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What Is an X-Ray?

What to Expect When Undergoing This Test

How It Works

  • When It's Used

Contraindications

How to prepare, during the test, after the test, interpreting results.

An X-ray, also known as radiography , is a medical imaging technique. It uses tiny amounts of electromagnetic radiation to create images of structures inside the body. These images can then be viewed on film or digitally.

X-rays often are done to view bones and teeth , making them helpful in diagnosing fractures (broken bones) and diseases such as arthritis . A healthcare provider may also order an X-ray to look at organs and structures inside the chest, including the lungs, heart, breasts, and abdomen.

This article explains when X-rays are used, how to prepare for one, and what to expect. It also covers the risks and benefits of the imaging test.

The tiny particles of electromagnetic radiation that an X-ray machine emits pass through all but the most solid objects in the body. As such, the image it creates, known as a radiograph, allows healthcare providers to visualize internal structures in your body.

What Is Electromagnetic Radiation?

Electromagnetic radiation (EMR) is a type of radiation that travels in waves and has electric and magnetic fields. Devices that use this type of radiation include X-rays, microwaves, radio waves, ultraviolet light, infrared light, visible light, and gamma rays.

Sometimes a contrast medium , a type of dye, is given to help images appear in greater detail. You might receive these via injection into a blood vessel, orally, or rectally.

X-ray images appear in various shades of white and grey. Because bones and metal objects are solid, less radiation passes through them, making them appear white on the radiograph. On the other hand, skin, muscle, blood and other fluids, and fat are grey because they allow most radiation to pass through.

Areas where there is nothing to stop the beam of radiation, such as air, or even a fracture, appear black compared to surrounding tissue.

When It's Used

X-ray technology is used for a multitude of purposes. For example, it can help healthcare providers evaluate symptoms and diagnose injuries.

Among the most common reasons for X-rays include:

  • Identifying fractures
  • Identifying infections in bones and teeth
  • Diagnosing cavities and evaluating structures in the mouth and jaw
  • Revealing bone tumors
  • Measuring bone density (the amount of mineral in your bones) to diagnose osteoporosis (a bone disease caused by bone loss)
  • Finding evidence of pneumonia, tuberculosis , or lung cancer
  • Looking for signs of heart failure or changes in blood flow to the lungs and heart
  • Revealing problems in the digestive tract, such as kidney stones , sometimes using a contrast medium called barium
  • Locating swallowed items such as a coin or tiny toy

This technology can also support other types of diagnostic procedures.

Fluoroscopy

During fluoroscopy , an X-ray image displays on a monitor in real time. Unlike X-ray images, which are still pictures, fluoroscopy is a moving image. Often, you will receive a contrast dye intravenously (in your vein) during this procedure.

Seeing moving images allows healthcare providers to follow the progression of a procedure (such as the placement of a stent). They can also view the contrast agent passing through the body.

Computed tomography (CT scan) is a technique that takes a series of individual images of internal organs and tissues. These “slices” are then combined to show a three-dimensional visualization.

CT scans can identify organ masses, see how well blood is flowing, observe brain hemorrhage and trauma, view lung structures, and diagnose injuries and diseases of the skeletal system.

Mammography

A mammogram is a breast cancer screening test that uses X-ray imaging. Mammograms can also diagnose breast lumps and other breast changes.

During a mammogram, your breasts are placed one at a time between two plates. A technician then presses them together to flatten your breast to get a clear picture. Finally, they X-ray your breasts from the front and sides.

Arthrography allows healthcare providers to identify signs of joint changes that indicate arthritis. It uses an X-ray and a special contrast dye injected directly into the joint.

Sometimes instead of X-rays, an arthrogram uses CT scan, fluoroscopy, or magnetic resonance imaging (MRI) technology.

Having an X-ray doesn't hurt and isn't particularly dangerous. However, there are a few things to be aware of and discuss with your healthcare provider.

Radiation Exposure

Having frequent X-rays carries a very low risk of developing cancer later in life. That is because the radiation has enough energy to potentially damage DNA .

There are varying estimates as to how significant this risk is. What is known is that fluoroscopy and computed tomography both expose the body to more radiation than a single conventional X-ray. The Food and Drug Administration (FDA) says that the risk of cancer from exposure to X-rays depends on:

  • Exposure frequency
  • Age at exposure
  • Which reproductive organs a person has
  • Area of the body exposed

The more times a person is exposed to radiation from medical imaging throughout their life and the larger the dose, the greater the risk of developing cancer. In addition, the lifetime risk of cancer is more significant for someone who's exposed to radiation at a younger age than for a person who has X-rays when they're older.

Studies have shown that those with female reproductive organs are at a somewhat higher lifetime risk for developing radiation-associated cancer. Researchers believe that since reproductive organs absorb more radiation and people with ovaries typically have more reproductive organs than those with testicles, this may be why.

It is essential to weigh the risks and benefits of having an X-ray, CT scan, or fluoroscopy with your healthcare provider. Ask if the imaging study will make an impact on your care. If not, it may be advisable to skip the test. However, if a diagnosis or potential changes in your treatment are likely to depend on the X-ray results, it will most likely be worth the minor risk.

Barium Sulfate Risks

There may be some minor risks associated with contrast mediums used during X-ray procedures, particularly for people who have asthma or other conditions.

Barium sulfate contrast materials are perfectly safe for most people. However, some circumstances can put a person at an increased risk of severe side effects such as throat swelling, difficulty breathing, and more. These include:

  • Having asthma or allergies , which increases the risk of an allergic reaction
  • Cystic fibrosis , which increases the risk of small bowel blockage
  • Severe dehydration, which may cause severe constipation
  • An intestinal blockage or perforation that could be made worse by the contrast agent

Iodine Risks

Iodine is another contrast medium used for X-rays. After exposure to this dye, a small percentage of people may develop delayed reaction hours or even days later. Most reactions are mild, but some can be more severe and cause the following:

  • Skin rash or hives
  • Abnormal heart rhythms
  • High or low blood pressure
  • Shortness of breath
  • Difficulty breathing
  • Throat swelling
  • Cardiac arrest
  • Convulsions

Given your overall health profile, a healthcare provider can help you determine if using a contrast agent is necessary and suitable for you.

Pregnant people are usually discouraged from having an X-ray unless it's vital. That's because there is a risk that the radiation from an X-ray could cause changes in developing fetal cells and thereby increase the risk of birth defects or cancer later in life. The risk of harm depends on a fetus's gestational age and the amount of radiation exposure.

That said, this recommendation is mainly precautionary. These risks are associated with very high doses of radiation, and a regular diagnostic X-ray does not expose you to high-dose radiation. Therefore, the benefits of what an X-ray could reveal often outweigh any risks.

If you need an X-ray during pregnancy, the following can reduce your risks:

  • Cover with a leaded apron or collar to block any scattered radiation
  • Avoid abdominal X-rays
  • Inform the X-ray technician if you are or could be pregnant

In addition, if you have a child who needs an X-ray, don't hold them during the procedure if you are or might be pregnant.

Often, an X-ray is done as part of a visit to a healthcare provider or emergency room to diagnose symptoms or evaluate an injury. X-rays also complement specific routine exams, such as dental checkups . These types of X-rays usually take place in a medical office or the hospital.

Other times, a healthcare provider recommends screening X-rays, like mammograms, at regular intervals. These are often performed at imaging centers or hospitals by appointment.

The setting in which you get an X-ray and its reasons will determine your overall testing experience.

It's impossible to generalize how long an entire X-ray procedure will take. For example, it can take just a few minutes to get an image or two of an injured bone in an emergency room. On the other hand, a CT scan appointment can take longer.

If you're scheduling an X-ray, ask your healthcare provider to give you an idea of how much time you should allow.

X-ray tests may take place in various locations, including:

  • Hospital imaging departments
  • Freestanding radiology and imaging clinics
  • Medical offices, particularly specialists such as orthopedics and dentists
  • Urgent care centers

What to Wear

Generally speaking, the X-ray tech will ask you to remove any clothing covering the X-rayed area. For some procedures that involve X-ray imaging, you'll need to wear a hospital gown. Therefore, you may want to choose clothing that's easy to change in and out of.

In addition, since metal can show up on an X-ray, you may need to remove your jewelry and eyeglasses before an X-ray.

Food and Drink

If you have an X-ray without contrast, you can usually eat and drink normally. However, if you are receiving a contrast agent, you may need to avoid consuming food and liquids for some time before.

For example, healthcare providers use barium to highlight structures in the digestive system . Therefore, they may tell you not to eat for at least three hours before your appointment.

People with diabetes are usually advised to eat a light meal three hours before receiving barium. However, suppose you receive the barium via an enema (a tube inserted into the rectum). In that case, you may also be asked to eat a special diet and take medication to cleanse your colon beforehand.

Cost and Health Insurance

Most health insurance policies will cover any medically necessary X-ray imaging. Of course, out-of-pocket costs vary and depend on the type of plan you have. For example, you may be responsible for a copay , or for the entire cost if you haven't met your deductible . Check with your insurance company to learn the specifics of your plan.

If you don't have insurance or you're paying out-of-pocket for an X-ray, the fee will depend on several things, including:

  • Which body part is imaged
  • The number of images taken
  • Whether a contrast dye is used

Similarly, if you are paying for your X-ray and have time to research the fees, you can call the hospital's billing department ahead of time to get a quote for the procedure. Doing so can help you know the cost you're obligated to pay.

What to Bring

You will need to have your insurance card with you at your X-ray. In addition, if your healthcare provider gave you a written order for the procedure, bring that as well.

Because X-ray procedures vary widely, it isn't easy to generalize the experience. So instead, ask your healthcare provider for details about what to expect in your specific case.

You may need to remove some or all of your clothing before the X-ray. A technician will escort you to a dressing room or other private area where you can change into a hospital gown. There will probably be a locker where you can safely store your clothing and other belongings.

If you have a test involving a contrast dye, you will receive that before your imaging procedure.

Healthcare providers may give contrast dyes in the following ways:

  • In a special drink you swallow
  • Intravenous (IV) line

Except for IV contrast dye, which allows for a constant stream of the material to be given, contrasts are administered before the X-ray. In other words, you will not have to wait for the dye to "take" before your imaging test.

How you receive the contrast depends on the substance used and what internal organs or structures your healthcare provider needs to view. For example, you might receive an iodine-based contrast dye injection into a joint for an arthrogram.

On the other hand, you might swallow a barium contrast to help illuminate your digestive system for fluoroscopy. Oral barium contrast dye may not taste good, but most people can tolerate the flavor long enough to swallow the prescribed amount.

If you have a barium enema, you may feel abdominal fullness and urgency to expel the liquid. However, the mild discomfort will not last long.

A conventional X-ray is taken in a special room with an X-ray machine. During the test, you will:

  • Place a leaded apron or cover over your torso
  • Stand, sit, or lie down on an X-ray table
  • Position your body in specific ways
  • Use props such as sandbags or pillows to adjust your position

Once positioned correctly, you will need to be very still. That's because even slight movement can cause an X-ray image to come out blurry. A technician may even ask you to hold your breath.

Infants and young children may need support being still. Guardians often accompany small children into the procedure room for this reason. If you attend your child for support, you will wear a leaded apron to limit your radiation exposure.

For their protection, the technician will step behind a protective window to operate the X-ray machine while also watching you. It only takes a few seconds to take the picture. However, often multiple angles of the body part are necessary. So, after your first image, the technician will likely adjust you or the machine and take another picture.

For a CT scan, you will lie down on a table that moved you into a cylindrical machine that rotates around you to take many pictures from all directions . You won't feel anything during a CT scan, but it may be uncomfortable for you if you dislike being in enclosed spaces.

When the tech has all the required images, you will remove the lead apron (if used) and leave the room. If you need to change back into your clothes, they'll direct you to the dressing area to change out of your hospital gown.

After you leave your appointment, you can return to your regular activities. If you received a contrast medium, a healthcare provider might instruct you to drink extra fluids to help flush the substance out of your system.

The barium-based dye comes out in your bowel movements, which will be white for a few days. You also may notice changes in your bowel movement patterns for 12 to 24 hours after your X-ray.

If you take Glucophage ( metformin ) or a related medication to treat type 2 diabetes, you need to stop taking your medicine for at least 48 hours after receiving contrast. That's because it may cause a condition called metabolic acidosis—an unsafe change in your blood pH (the balance of acidic or alkaline substances in the body).

Barium Side Effects

Keep an eye on the injection site if you received contrast dye by injection. Call your healthcare provider if you experience signs of infection, like pain, swelling, or redness.

Barium contrast materials can cause some digestive tract problems. If these become severe or don't go away, see your healthcare provider. These side effects include:

  • Stomach cramps
  • Nausea and vomiting
  • Constipation

Iodine Side Effects

Likewise, iodine contrast can cause symptoms. Let your healthcare provider know if you begin to have even mild symptoms after receiving iodine contrast. These symptoms include:

  • Mild skin rash and hives

Severe Side Effects

Call your healthcare provider immediately or go to the emergency room if you experience signs of anaphylaxis , a severe allergic reaction, including:

  • Swelling of the throat
  • Difficulty breathing or swallowing
  • Fast heartbeat
  • Bluish skin color

A radiologist specializing in analyzing imaging tests interprets the images from your X-ray. They then send the results and a report to your healthcare provider. Often, they will call you or have you come in to discuss the findings. In emergencies, you should receive these results soon after your X-ray.

Any follow-up tests or treatment will depend on your particular situation. For example, if you have an X-ray to determine the extent of an injury to a bone and it reveals you have a break, the bone will need to be set . Likewise, a breast tumor revealed during mammography may require a follow-up biopsy to determine if it is malignant (cancerous) or benign (non-cancerous).

X-rays are imaging tests that use small amounts of electromagnetic radiation to view the inside structures of your body. In addition to conventional X-rays, several other specialized forms of X-rays capture images in more precise ways. Sometimes a contrast agent can help healthcare providers see things better. These dyes might be given via injection, IV, orally, or rectally.

X-rays don't typically require preparation unless you are receiving contrast. In that case, you may need to avoid food and drinks for a few hours beforehand. X-rays do not take long—usually just a few minutes. Often, a technician takes multiple angles and images of the area. Afterward, you will be able to leave right away. If you received contrast, you might notice side effects. You should tell your healthcare provider about any symptoms you experience.

A Word From Verywell

For the majority of people, X-rays are harmless. However, if you have to have multiple X-rays over a lifetime, you may be at increased cancer risk. As such, it's essential to talk to your healthcare provider before you have an X-ray to make sure you have all the information you need to make an informed decision. And if you are or could be pregnant, tell the technician before undergoing the procedure.

National Cancer Institute. Electromagnetic radiation .

U.S. National Library of Medicine MedlinePlus. X-rays .

U.S. Food & Drug Administration. Medical x-ray imaging .

Johns Hopkins Medicine. Arthrography .

Narendran N, Luzhna L, Kovalchuk O. Sex difference of radiation response in occupational and accidental exposure . Front Genet . 2019;10:260. doi:10.3389/fgene.2019.00260

RadiologyInfo.org. Contrast materials .

U.S. Food & Drug Administration. X-rays, pregnancy and you .

RadiologyInfo.org.  X-ray (radiography) .

RadiologyInfo.org. Pediatric X-ray (radiography) .

Johns Hopkins Medicine. What are X-rays?

U.S. Food and Drug Administration. Medical X-ray imaging .

By Kristin Hayes, RN Kristin Hayes, RN, is a registered nurse specializing in ear, nose, and throat disorders for both adults and children.

  • Patient Care & Health Information
  • Tests & Procedures

An X-ray is a quick, painless test that captures images of the structures inside the body — particularly the bones.

X-ray beams pass through the body. These beams are absorbed in different amounts depending on the density of the material they pass through. Dense materials, such as bone and metal, show up as white on X-rays. The air in the lungs shows up as black. Fat and muscle appear as shades of gray.

For some types of X-ray tests, a contrast medium — such as iodine or barium — is put into the body to get greater detail on the images.

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Why it's done

X-ray of knee arthritis

X-ray of knee arthritis

Knee arthritis can affect one side of the joint more than the other. This X-ray image shows how the cushioning cartilage has worn away, allowing bone to touch bone.

Medical image of chest X-rays

  • Chest X-ray

A chest X-ray helps detect problems with the heart and lungs. The chest X-ray on the left is typical. The image on the right shows a mass in the right lung.

X-ray of swallowed jack

  • X-ray of swallowed jack

X-rays can locate metal objects your child has swallowed, such as this jack.

X-ray technology is used to examine many parts of the body.

Bones and teeth

  • Fractures and infections. In most cases, fractures and infections in bones and teeth show up clearly on X-rays.
  • Arthritis. X-rays of the joints can show evidence of arthritis. X-rays taken over the years can help your healthcare team tell if your arthritis is worsening.
  • Dental decay. Dentists use X-rays to check for cavities in the teeth.
  • Osteoporosis. Special types of X-ray tests can measure bone density.
  • Bone cancer. X-rays can reveal bone tumors.
  • Lung infections or conditions. Evidence of pneumonia, tuberculosis or lung cancer can show up on chest X-rays.
  • Breast cancer. Mammography is a special type of X-ray test used to examine breast tissue.
  • Enlarged heart. This sign of congestive heart failure shows up clearly on X-rays.
  • Blocked blood vessels. Injecting a contrast material that contains iodine can help highlight sections of the circulatory system so they can be seen easily on X-rays.
  • Digestive tract issues. Barium, a contrast medium delivered in a drink or an enema, can help show problems in the digestive system.
  • Swallowed items. If a child has swallowed something such as a key or a coin, an X-ray can show the location of that object.

More Information

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  • Acute coronary syndrome
  • Acute lymphocytic leukemia
  • Adult Still disease
  • Ambiguous genitalia
  • Anal cancer
  • Ankylosing spondylitis
  • Anorexia nervosa
  • Aspergillosis
  • Atrial fibrillation
  • Atrial septal defect (ASD)
  • Avascular necrosis (osteonecrosis)
  • Bed-wetting
  • Bell's palsy
  • Bladder stones
  • Blastocystis hominis
  • Bone cancer
  • Breast cancer
  • Broken ankle
  • Broken collarbone
  • Broken foot
  • Broken hand
  • Broken nose
  • Broken ribs
  • Broken wrist
  • Brucellosis
  • Bulimia nervosa
  • Carcinoid tumors
  • Carpal tunnel syndrome
  • Castleman disease
  • Cavities and tooth decay
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  • Hodgkin's lymphoma (Hodgkin's disease)
  • Horner syndrome
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  • Impacted wisdom teeth
  • Indigestion
  • Infant reflux
  • Inflammatory bowel disease (IBD)
  • Intestinal obstruction
  • Intussusception
  • Invasive lobular carcinoma
  • Juvenile idiopathic arthritis
  • Knee bursitis
  • Legg-Calve-Perthes disease
  • Lung cancer
  • Male breast cancer
  • Meralgia paresthetica
  • Metatarsalgia
  • Morton's neuroma
  • Mouth cancer
  • Multiple myeloma
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  • Non-Hodgkin's lymphoma
  • Osteoarthritis
  • Osteochondritis dissecans
  • Osteomyelitis
  • Paget's disease of bone
  • Paget's disease of the breast
  • Patellar tendinitis
  • Patellofemoral pain syndrome
  • Peptic ulcer
  • Peyronie disease
  • Plantar fasciitis
  • Posterior vaginal prolapse (rectocele)
  • Precocious puberty
  • Pseudomembranous colitis
  • Psoriatic arthritis
  • Pulmonary atresia
  • Pulmonary atresia with intact ventricular septum
  • Pulmonary atresia with ventricular septal defect
  • Pyloric stenosis
  • Reactive arthritis
  • Recurrent breast cancer
  • Residual limb pain
  • Rotator cuff injury
  • Sacroiliitis
  • Sarcoidosis
  • Septic arthritis
  • Shaken baby syndrome
  • Shin splints
  • Spinal cord injury
  • Spinal stenosis
  • Sprained ankle
  • Stress fractures
  • Swollen knee
  • Takayasu's arteritis
  • Tapeworm infection
  • Tennis elbow
  • Thoracic outlet syndrome
  • Throat cancer
  • Thumb arthritis
  • Tooth abscess
  • Torn meniscus
  • Ulcerative colitis
  • Umbilical hernia
  • Vaginal cancer
  • Vascular dementia
  • Vocal cord paralysis

Radiation exposure

Some people worry that X-rays aren't safe. This is because radiation exposure can cause cell changes that may lead to cancer. The amount of radiation you're exposed to during an X-ray depends on the tissue or organ being examined. Sensitivity to the radiation depends on your age, with children being more sensitive than adults.

Generally, however, radiation exposure from an X-ray is low, and the benefits from these tests far outweigh the risks.

However, if you are pregnant or suspect that you may be pregnant, tell your healthcare team before having an X-ray. Though most diagnostic X-rays pose only small risk to an unborn baby, your care team may decide to use another imaging test, such as ultrasound.

Contrast medium

In some people, the injection of a contrast medium can cause side effects such as:

  • A feeling of warmth or flushing.
  • A metallic taste.
  • Lightheadedness.

Rarely, severe reactions to a contrast medium occur, including:

  • Very low blood pressure.
  • Difficulty breathing.
  • Swelling of the throat or other parts of the body.

How you prepare

X-ray image of kidney stone

  • X-ray image of kidney stone

This X-ray using contrast reveals a kidney stone at the junction of the kidney and the tube that connects the kidney to the bladder, called the ureter.

A person having an X-ray exam

The X-ray tube is focused on the abdomen. X-rays will pass through the body and produce an image on the specialized plate below.

Different types of X-rays require different preparations. Ask your healthcare team to provide you with specific instructions.

What to wear

In general, you undress whatever part of your body needs examination. You may wear a gown during the exam depending on which area is being X-rayed. You also may be asked to remove jewelry, eyeglasses and any metal objects because they can show up on an X-ray.

Contrast material

Before having some types of X-rays, you're given a liquid called contrast medium. Contrast mediums, such as barium and iodine, help outline a specific area of your body on the X-ray image. You may swallow the contrast medium or receive it as an injection or an enema.

What you can expect

During the x-ray.

X-rays are performed at medical offices, dentists' offices, emergency rooms and hospitals — wherever an X-ray machine is available. The machine produces a safe level of radiation that passes through the body and records an image on a specialized plate. You can't feel an X-ray.

A technologist positions your body to get the necessary views. Pillows or sandbags may be used to help you hold the position. During the X-ray exposure, you remain still and sometimes hold your breath to avoid moving so that the image doesn't blur.

An X-ray procedure may take just a few minutes for a simple X-ray or longer for more-involved procedures, such as those using a contrast medium.

Your child's X-ray

If a young child is having an X-ray, restraints or other tools may be used to keep the child still. These won't harm the child and they prevent the need for a repeat procedure, which may be necessary if the child moves during the X-ray exposure.

You may be allowed to remain with your child during the test. If you remain in the room during the X-ray exposure, you'll likely be asked to wear a lead apron to shield you from unnecessary X-ray exposure.

After the X-ray

After an X-ray, you generally can resume usual activities. Routine X-rays usually have no side effects. However, if you're given contrast medium before your X-ray, drink plenty of fluids to help rid your body of the contrast. Call your healthcare team if you have pain, swelling or redness at the injection site. Ask your team about other symptoms to watch for.

X-rays are saved digitally on computers and can be viewed on-screen within minutes. A radiologist typically views and interprets the results and sends a report to a member of your healthcare team, who then explains the results to you. In an emergency, your X-ray results can be made available in minutes.

  • X-rays. National Institute of Biomedical Imaging and Bioengineering. https://www.nibib.nih.gov/science-education/science-topics/x-rays. Accessed Nov. 7, 2023.
  • Patient safety: Contrast materials. Radiological Society of North America. https://www.radiologyinfo.org/en/info/safety-contrast. Accessed Nov. 7, 2023.
  • Chest X-ray. Radiological Society of North America. https://www.radiologyinfo.org/en/info/chestrad. Accessed Nov. 7, 2023.
  • Bone X-ray (radiography). Radiological Society of North America. https://www.radiologyinfo.org/en/info/bonerad. Accessed Nov. 7, 2023.
  • Pediatric X-ray. Radiological Society of North America. https://www.radiologyinfo.org/en/info/pediatric-xray. Accessed Nov. 7, 2023.
  • Panoramic dental X-ray. Radiological Society of North America. https://www.radiologyinfo.org/en/info/panoramic-xray. Accessed Nov. 7, 2023.
  • Lee CI, et al. Radiation-related risks of imaging. https://www.uptodate.com/contents/search. Accessed Nov. 7, 2023.
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X-ray (Radiography)

Infographic about x-ray describing its function, strengths, and benefits.

For the benefits and risks of a specific x-ray procedure, how to prepare, and more, select a topic below.

Abdominal X-ray

Myelography

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Panoramic Dental X-ray

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Catheter Angiography

Pediatric VCUG

Chest X-ray

Pediatric X-ray

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Radiation Dose

Facet Joint Block

Radiation Safety

Fetal and Gonadal Shielding

Radiation Safety for Children

Fistulogram/Sinogram

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Plain Film X-Ray

Original Author(s): Stuart Jones and Chris Quach (Pulse Radiology) Last updated: December 8, 2018 Revisions: 14

Plain film x-ray  is the most common diagnostic radiological modality used in hospitals today. They were first discovered and used for imaging purposes by Wilhelm Röntgen on 8th November 1895, when he took an image of his wife’s hand.

In this article, we shall look at the basic science underpinning x-rays, and the principles of their interpretation.

Basic Principles

X-rays are a type of electromagnetic radiation (just like visible light). There are three criteria that must be met to allow electromagnetic radiation to be used for imaging purposes:

  • Ability to create to the electromagnetic radiation at the wavelength required
  • Ability to focus the radiation on a particular area
  • Ability to detect the radiation once it has passed through the patient.

The radiation is created when an electric current is generated from a high voltage generator. This causes electrons to “boil-off” from the cathode end of an X-ray tube assembly. These electrons are emitted from a filament on the cathode and rush towards a target material known as the anode . This process is known as thermionic emission .

The electrons emitted by the cathode rush towards the anode, which holds a disc made of tungsten. When the electrons collide with the tungsten, several interactions occur at the atomic level. One of these interactions causes electrons to be expelled from the outer orbits of the atoms releasing a X-ray photon . Energy levels of the X-ray photon will vary and can be adjusted when selecting a parameter known as kVP or kilovolts peak.

These X-rays then travel through a focusing cup , focusing and accelerating the photons towards the area of the body to be imaged. Traditionally, radiographic film was used known as double emulsion film containing silver nitrate. With technological advancements, many instutions will be using a cassette receptor or if newer technology is available, a digital plate receptor may be used instead. These receptors are placed behind the patient to capture the x-ray photons that are transmitted through the patient and ultimately form the image.

summary of x ray

Fig 1 – How an x-ray is generated.

Interpreting an X-Ray

The interpretation of an x-ray film requires sound anatomical knowledge, and an understanding that different tissue types absorb x-rays to varying degrees:

  • High density tissue (e.g. bone) – absorb x-rays to a greater degree, and appear white on the film.
  • Low density tissue (e.g the lungs) – absorb x-rays to a lesser degree, and appear black on the film.
  • Intermediate density tissue (e.g. muscle and fat) – appears as shades of grey on the x-ray film.

It is important to appreciate that x-rays only give a 2D superimposed view of the body part that has been imaged. Therefore, it may be necessary to take multiple views of the same area from different angle (e.g. in cases of suspected fracture), to gain a full understanding of the injury.

summary of x ray

Fig 2 – Illustration of the mediastinal structures in a normal chest radiograph.

Comparison to Other Imaging Techniques

The biggest advantage with plain film X-rays is the amount of radiation involved. It offers lower dosage compared to CT, and certain studies are performed relatively quickly (Chest X-rays). They are often used as an initial screening to rule out anything obvious before an advanced modality is used such as CT or MR.

However, plain film X-rays procedures are being replaced by CT and MR due to advancements in technology. There are CT scanners available on the market now that offer radiation dosage levels as low as plain film X-rays.

Below is a summary table of the common imaging modalities. Depending on the tissue being imaged, the urgency of the investigation and the level of detail required, any of these techniques may be preferred:

Plain film x-ray  is the most common diagnostic radiological modality used in hospitals today. They were first discovered and used for imaging purposes by Wilhelm Röntgen on 8th November 1895, when he took an image of his wife's hand.

  • Intermediate density tissue (e.g. muscle and fat) - appears as shades of grey on the x-ray film.

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  • with wavelengths in the approximate range of 10 −9  m to 10 −12  m (1 nm to 1 pm)
  • with photon energies in the approximate range of 10 3  eV to 10 6  eV (1 keV to 1 MeV)
  • called bremsstrahlung (from the German term for "braking radiation")
  • called synchrotron radiation (since they were first detected in ring-shaped particle accelerators called synchrotrons)
  • called characteristic x-rays (since the wavelengths emitted are a characteristic of the element)
  • U.S. Department of Health & Human Services
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What are medical x-rays?

How do medical x-rays work, when are medical x-rays used, are there risks, what are nibib-funded researchers developing in the field of x-ray technology.

X-rays are a form of electromagnetic radiation, similar to visible light. Unlike light, however, x-rays have higher energy and can pass through most objects, including the body. Medical x-rays are used to generate images of tissues and structures inside the body. If x-rays traveling through the body also pass through an x-ray detector on the other side of the patient, an image will be formed that represents the “shadows” formed by the objects inside of the body.

One type of x-ray detector is photographic film, but there are many other types of detectors that are used to produce digital images. The x-ray images that result from this process are called radiographs.

graphic explaining the electromagnetic spectrum, ranging from radio waves to gamma rays

To create a radiograph, a patient is positioned so that the part of the body being imaged is located between an x-ray source and an x-ray detector. When the machine is turned on, x-rays travel through the body and are absorbed in different amounts by different tissues, depending on the radiological density of the tissues they pass through. Radiological density is determined by both the density and the atomic number (the number of protons in an atom’s nucleus) of the material being imaged. For example, our bones contain calcium, which has a higher atomic number than most other tissues. Because of this property, bones readily absorb x-rays and therefore produce high contrast on the x-ray detector. As a result, bony structures appear whiter than other tissues against the black background of a radiograph. Conversely, x-rays travel more easily through less radiologically dense tissues, such as fat, muscle, and air-filled cavities such as the lungs. These structures are displayed in shades of gray on a radiograph.

Listed below are examples of examinations and procedures that use x-ray technology to either diagnose or treat disease:

X-ray radiography:  Detects bone fractures, certain tumors and other abnormal masses, pneumonia, some types of injuries, calcifications, foreign objects, or dental problems.

An x-ray system

Mammography:  A radiograph of the breast that is used for cancer detection and diagnosis. Tumors tend to appear as regular or irregular-shaped masses that are somewhat brighter than the background on the radiograph (i.e., whiter on a black background or blacker on a white background). Mammograms can also detect tiny bits of calcium, called microcalcifications, which show up as very bright specks on a mammogram. While usually benign, specific patterns of microcalcifications could indicate the presence of cancer. Learn more about mammography here .

Computed tomography (CT):  Combines traditional x-ray technology with computer processing to generate a series of cross-sectional images of the body that can later be combined to form a three-dimensional x-ray image. CT images are more detailed than plain radiographs and give doctors the ability to view structures within the body from many different angles. Learn more about CT here .

Fluoroscopy:  Uses x-rays and a fluorescent screen to obtain real-time images of movement within the body or to view diagnostic processes, such as following the path of an injected or swallowed contrast agent. For example, fluoroscopy is used to view the movement of the beating heart, and, with the aid of radiographic contrast agents, to view blood flow to the heart muscle as well as through blood vessels and organs. This technology is also used with a radiographic contrast agent to guide an internally threaded catheter during cardiac angioplasty, which is a minimally invasive procedure for opening clogged arteries that supply blood to the heart.

Therapeutic

Radiation therapy in cancer treatment:  X-rays and other types of high-energy radiation can be used to destroy cancerous tumors and cells by damaging their DNA. The radiation dose used for treating cancer is much higher than the radiation dose used for diagnostic imaging. Therapeutic radiation can come from a machine outside of the body or from a radioactive material that is placed in the body, inside or near tumor cells, or injected into the blood stream. Learn more about radiation treatment for cancer therapy here .

When used appropriately, the diagnostic benefits of x-ray scans significantly outweigh the risks. X-ray scans can diagnose possibly life-threatening conditions such as blocked blood vessels, bone cancer, and infections. However, x-rays produce ionizing radiation—a form of radiation that has the potential to harm living tissue. This is a risk that increases with the number of exposures added up over the life of an individual. However, the risk of developing cancer from radiation exposure is generally small.

An x-ray in a pregnant woman poses no known risks to the baby if the area of the body being imaged isn’t the abdomen or pelvis. In general, if imaging of the abdomen and pelvis is needed, doctors prefer to use exams that do not use radiation, such as magnetic resonance imaging (MRI) or ultrasound. However, if neither of those can provide the answers needed, or there is an emergency or other time constraint, an x-ray may be an acceptable alternative imaging option.

Because children are more sensitive to ionizing radiation and have a longer life expectancy, they have a higher relative risk for developing cancer from such radiation compared with adults. Parents may want to ask the technologist or doctor if their machine settings have been adjusted for children.

Learn more about specific risks involved with CT and mammography .

Current research of x-ray technology focuses on ways to reduce radiation dose, improve image resolution, and enhance contrast materials and methods. The following are examples of research projects funded by NIBIB that are developing new applications of x-ray technology:

X-ray of a broken arm

Single-frame x-ray tomosynthesis (SFXT): Conventional x-ray radiography generates a single two-dimensional image, which is created by imaging a single plane at a single time point. X-ray tomosynthesis, on the other hand, uses multiple images, which are then reconstructed to generate more information, such as a three-dimensional image. Unlike CT imaging, where the source/detector physically travels at least 180 degrees around the patient, tomosynthesis uses a limited rotational angle and takes fewer images (requiring less radiation and less expense). Current tomosynthesis approaches, however, generate a static snapshot of the tissue of interest and do not allow for real-time imaging.

NIBIB-funded researchers are working on a new x-ray method, called single-frame x-ray tomosynthesis (or SFXT), that would allow for real-time monitoring of a small area of tissue. By capturing 30 images every second, this technique would have 10 to 100 times the temporal resolution of conventional tomosynthesis, resulting in “sharper” images of tissues in motion (similar to using a faster shutter speed on a camera). The researchers plan to evaluate the use of SFXT in the detection of cardiovascular disease — by looking at calcium deposits in the coronary arteries — and to guide radiation treatment to precise locations in the lungs, which would enable safer ablation of lung tumors.

Imaging to guide lung biopsies: Lung cancer is the leading cause of cancer-related mortality in the United States, and analyzing lesions found in the lungs is a way to screen for the disease and to guide treatment. For a biopsy , one method to obtain lung tissue is through a bronchoscopy, where a thin tube is passed through the nose or mouth and guided into the lungs. However, obtaining tissues of interest remains difficult, as locating and visualizing such lesions is challenging. To overcome these limitations, researchers have developed a new, cost-effective chest x-ray tomosynthesis system that can generate high-resolution, real-time images of the lungs, which would allow for improved visualization during a transbrochial biopsy. In addition to being less expensive and easier to use than standard CT-based approaches, this x-ray technique is stationary and does not require any physical motion of the x-ray source or detector. Further, this method uses low doses of radiation, which would be beneficial for patients who require multiple biopsies. This x-ray system is currently being optimized for pre-clinical large animal evaluation.

Learn more about how X-rays work here .

Updated June 2022

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Physics LibreTexts

30.4: X Rays - Atomic Origins and Applications

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Learning Objectives

By the end of this section, you will be able to:

  • Define x-ray tube and its spectrum.
  • Show the x-ray characteristic energy.
  • Specify the use of x rays in medical observations.
  • Explain the use of x rays in CT scanners in diagnostics.

Each type of atom (or element) has its own characteristic electromagnetic spectrum. X rays lie at the high-frequency end of an atom’s spectrum and are characteristic of the atom as well. In this section, we explore characteristic x rays and some of their important applications.

We have previously discussed x rays as a part of the electromagnetic spectrum in Photon Energies and the Electromagnetic Spectrum . That module illustrated how an x-ray tube (a specialized CRT) produces x rays. Electrons emitted from a hot filament are accelerated with a high voltage, gaining significant kinetic energy and striking the anode.

There are two processes by which x rays are produced in the anode of an x-ray tube. In one process, the deceleration of electrons produces x rays, and these x rays are called bremsstrahlung , or braking radiation. The second process is atomic in nature and produces characteristic x rays , so called because they are characteristic of the anode material. The x-ray spectrum in Figure is typical of what is produced by an x-ray tube, showing a broad curve of bremsstrahlung radiation with characteristic x-ray peaks on it.

A graph of X-ray intensity versus frequency is shown. The curve starts from a point near the origin in the first quadrant and increases. Before the frequency attains its maximum value, two sharp peaks are formed, after which the X-ray intensity decreases sharply to zero at f max. Below the graph appears the equation q V equals h f max.

The spectrum in Figure is collected over a period of time in which many electrons strike the anode, with a variety of possible outcomes for each hit. The broad range of x-ray energies in the bremsstrahlung radiation indicates that an incident electron’s energy is not usually converted entirely into photon energy. The highest-energy x ray produced is one for which all of the electron’s energy was converted to photon energy. Thus the accelerating voltage and the maximum x-ray energy are related by conservation of energy. Electric potential energy is converted to kinetic energy and then to photon energy, so that \(E_{max} = hf_{max} = q_eV\). Units of electron volts are convenient. For example, a 100-kV accelerating voltage produces x-ray photons with a maximum energy of 100 keV.

Some electrons excite atoms in the anode. Part of the energy that they deposit by collision with an atom results in one or more of the atom’s inner electrons being knocked into a higher orbit or the atom being ionized. When the anode’s atoms de-excite, they emit characteristic electromagnetic radiation. The most energetic of these are produced when an inner-shell vacancy is filled—that is, when an \(n = 1\) or \(n = 2\) shell electron has been excited to a higher level, and another electron falls into the vacant spot. A characteristic x ray (see Photon Energies and the Electromagnetic Spectrum ) is electromagnetic (EM) radiation emitted by an atom when an inner-shell vacancy is filled. Figure shows a representative energy-level diagram that illustrates the labeling of characteristic x rays. X rays created when an electron falls into an \(n = 1\) shell vacancy are called \(K_a\) when they come from the next higher level; that is, an \(n = 2\) to \(n = 1\) transition. The labels \(K, \, L, \, M, . . . \) come from the older alphabetical labeling of shells starting with \(K\) rather than using the principal quantum numbers 1, 2, 3, …. A more energetic \(K_{\beta}\) x ray is produced when an electron falls into an \(n = 1\) shell vacancy from the \(n = 3\) shell; that is, an the \(n = 3\) to the \(n = 1\) transition. Similarly, when an electron falls into the the \(n = 2\) shell from the the \(n = 3\) shell, an \(L_{\alpha}\) x ray is created. The energies of these x rays depend on the energies of electron states in the particular atom and, thus, are characteristic of that element: every element has it own set of x-ray energies. This property can be used to identify elements, for example, to find trace (small) amounts of an element in an environmental or biological sample.

Different energy levels are shown in the form of horizontal lines. The line at the bottom shows the energy level for n is equal to one for the K shell. At a distance above this line, another horizontal line shows the energy level for n is equal to two for the shell L. Similarly, other lines are shown for the shells M and N. As we move from bottom to the top, the distance between the lines decreases, and near the end a few lines are shown very close to each other. Each level is labeled according to the characteristic x ray of the shell.

Example \(\PageIndex{1}\): Characteristic X-Ray Energy

Calculate the approximate energy of a \(K_{\alpha}\)

x ray from a tungsten anode in an x-ray tube.

How do we calculate energies in a multiple-electron atom? In the case of characteristic x rays, the following approximate calculation is reasonable. Characteristic x rays are produced when an inner-shell vacancy is filled. Inner-shell electrons are nearer the nucleus than others in an atom and thus feel little net effect from the others. This is similar to what happens inside a charged conductor, where its excess charge is distributed over the surface so that it produces no electric field inside. It is reasonable to assume the inner-shell electrons have hydrogen-like energies, as given by \(E_n = -\frac{Z^2}{n^2} E_0 (n = 1, \, 2, \, 3, . . .)\). As noted, a \(K_a\) x ray is produced by an \(n = 2\) to \(n = 1\) transition. Since there are two electrons in a filled \(K\) shell, a vacancy would leave one electron, so that the effective charge would be \(Z - 1\) rather than \(Z\). For tungsten, \(Z = 74\), so that the effective charge is 73.

\(E_n = - \frac{Z^2}{n^2}E_0(n = 1, \, 2, \, 3, . . .)\) gives the orbital energies for hydrogen-like atoms to be \(E_n = -(Z^2/n^2)E_0\), where \(E_0 = 13.6 \, eV\). As noted, the effective \(Z\) is 73. Now the \(K_{\alpha}\) x-ray energy is given by \[E_{K_{\alpha}} = \Delta E = E_i - E_f = E_2 - E_1,\] where \[E_1 = -\dfrac{Z^2}{1^2}E_0 = - \dfrac{73^2}{1} \left(13.6 \, eV\right) = - 72.5 \, keV\] and \[E_2 = - \dfrac{Z^2}{2^2} E_0 = - \dfrac{73^2}{4}\left(13.6 \, eV\right) = -18.1 \, keV.\] Thus, \[E_{K_{\alpha}} = -18.1 \, keV - (- 72.5 \, keV) = 54.4 \, keV.\]

This large photon energy is typical of characteristic x rays from heavy elements. It is large compared with other atomic emissions because it is produced when an inner-shell vacancy is filled, and inner-shell electrons are tightly bound. Characteristic x ray energies become progressively larger for heavier elements because their energy increases approximately as \(Z^2\). Significant accelerating voltage is needed to create these inner-shell vacancies. In the case of tungsten, at least 72.5 kV is needed, because other shells are filled and you cannot simply bump one electron to a higher filled shell. Tungsten is a common anode material in x-ray tubes; so much of the energy of the impinging electrons is absorbed, raising its temperature, that a high-melting-point material like tungsten is required.

Medical and Other Diagnostic Uses of X-rays

All of us can identify diagnostic uses of x-ray photons. Among these are the universal dental and medical x rays that have become an essential part of medical diagnostics. (See Figure and Figure .) X rays are also used to inspect our luggage at airports, as shown in Figure , and for early detection of cracks in crucial aircraft components. An x ray is not only a noun meaning high-energy photon, it also is an image produced by x rays, and it has been made into a familiar verb—to be x-rayed.

The X-ray image of front view of the jaw, especially the teeth.

The most common x-ray images are simple shadows. Since x-ray photons have high energies, they penetrate materials that are opaque to visible light. The more energy an x-ray photon has, the more material it will penetrate. So an x-ray tube may be operated at 50.0 kV for a chest x ray, whereas it may need to be operated at 100 kV to examine a broken leg in a cast. The depth of penetration is related to the density of the material as well as to the energy of the photon. The denser the material, the fewer x-ray photons get through and the darker the shadow. Thus x rays excel at detecting breaks in bones and in imaging other physiological structures, such as some tumors, that differ in density from surrounding material. Because of their high photon energy, x rays produce significant ionization in materials and damage cells in biological organisms. Modern uses minimize exposure to the patient and eliminate exposure to others. Biological effects of x rays will be explored in the next chapter along with other types of ionizing radiation such as those produced by nuclei.

As the x-ray energy increases, the Compton effect (see Photon Momentum ) becomes more important in the attenuation of the x rays. Here, the x ray scatters from an outer electron shell of the atom, giving the ejected electron some kinetic energy while losing energy itself. The probability for attenuation of the x rays depends upon the number of electrons present (the material’s density) as well as the thickness of the material. Chemical composition of the medium, as characterized by its atomic number \(Z\), is not important here. Low-energy x rays provide better contrast (sharper images). However, due to greater attenuation and less scattering, they are more absorbed by thicker materials. Greater contrast can be achieved by injecting a substance with a large atomic number, such as barium or iodine. The structure of the part of the body that contains the substance (e.g., the gastro-intestinal tract or the abdomen) can easily be seen this way.

Breast cancer is the second-leading cause of death among women worldwide. Early detection can be very effective, hence the importance of x-ray diagnostics. A mammogram cannot diagnose a malignant tumor, only give evidence of a lump or region of increased density within the breast. X-ray absorption by different types of soft tissue is very similar, so contrast is difficult; this is especially true for younger women, who typically have denser breasts. For older women who are at greater risk of developing breast cancer, the presence of more fat in the breast gives the lump or tumor more contrast. MRI (Magnetic resonance imaging) has recently been used as a supplement to conventional x rays to improve detection and eliminate false positives. The subject’s radiation dose from x rays will be treated in a later chapter.

A standard x ray gives only a two-dimensional view of the object. Dense bones might hide images of soft tissue or organs. If you took another x ray from the side of the person (the first one being from the front), you would gain additional information. While shadow images are sufficient in many applications, far more sophisticated images can be produced with modern technology. Figure shows the use of a computed tomography (CT) scanner, also called computed axial tomography (CAT) scanner. X rays are passed through a narrow section (called a slice) of the patient’s body (or body part) over a range of directions. An array of many detectors on the other side of the patient registers the x rays. The system is then rotated around the patient and another image is taken, and so on. The x-ray tube and detector array are mechanically attached and so rotate together. Complex computer image processing of the relative absorption of the x rays along different directions produces a highly-detailed image. Different slices are taken as the patient moves through the scanner on a table. Multiple images of different slices can also be computer analyzed to produce three-dimensional information, sometimes enhancing specific types of tissue, as shown in Figure . G. Hounsfield (UK) and A. Cormack (US) won the Nobel Prize in Medicine in 1979 for their development of computed tomography.

A photographic image taken through the port of a C T scanner, showing a patient on a stretcher surrounded by three nursing staff and a doctor who are taking the patient’s C T scan.

X-Ray Diffraction and Crystallography

Since x-ray photons are very energetic, they have relatively short wavelengths. For example, the 54.4-keV \(K_{\alpha}\) x ray of Example has a wavelength \(\lambda = hc/E = 0.0228 \, nm\). Thus, typical x-ray photons act like rays when they encounter macroscopic objects, like teeth, and produce sharp shadows; however, since atoms are on the order of 0.1 nm in size, x rays can be used to detect the location, shape, and size of atoms and molecules. The process is called x-ray diffraction , because it involves the diffraction and interference of x rays to produce patterns that can be analyzed for information about the structures that scattered the x rays. Perhaps the most famous example of x-ray diffraction is the discovery of the double-helix structure of DNA in 1953 by an international team of scientists working at the Cavendish Laboratory—American James Watson, Englishman Francis Crick, and New Zealand–born Maurice Wilkins. Using x-ray diffraction data produced by Rosalind Franklin, they were the first to discern the structure of DNA that is so crucial to life. For this, Watson, Crick, and Wilkins were awarded the 1962 Nobel Prize in Physiology or Medicine. There is much debate and controversy over the issue that Rosalind Franklin was not included in the prize.

Figure shows a diffraction pattern produced by the scattering of x rays from a crystal. This process is known as x-ray crystallography because of the information it can yield about crystal structure, and it was the type of data Rosalind Franklin supplied to Watson and Crick for DNA. Not only do x rays confirm the size and shape of atoms, they give information on the atomic arrangements in materials. For example, current research in high-temperature superconductors involves complex materials whose lattice arrangements are crucial to obtaining a superconducting material. These can be studied using x-ray crystallography.

An x ray diffraction image, which resembles a structured array of small black dots on a white background. A white arm extends from the top left to the center of the image, where there is a small white disk. This white disk is the shadow of the beam block, which blocks the part of the incident x ray beam that was not diffracted by the crystal.

Historically, the scattering of x rays from crystals was used to prove that x rays are energetic EM waves. This was suspected from the time of the discovery of x rays in 1895, but it was not until 1912 that the German Max von Laue (1879–1960) convinced two of his colleagues to scatter x rays from crystals. If a diffraction pattern is obtained, he reasoned, then the x rays must be waves, and their wavelength could be determined. (The spacing of atoms in various crystals was reasonably well known at the time, based on good values for Avogadro’s number.) The experiments were convincing, and the 1914 Nobel Prize in Physics was given to von Laue for his suggestion leading to the proof that x rays are EM waves. In 1915, the unique father-and-son team of Sir William Henry Bragg and his son Sir William Lawrence Bragg were awarded a joint Nobel Prize for inventing the x-ray spectrometer and the then-new science of x-ray analysis. The elder Bragg had migrated to Australia from England just after graduating in mathematics. He learned physics and chemistry during his career at the University of Adelaide. The younger Bragg was born in Adelaide but went back to the Cavendish Laboratories in England to a career in x-ray and neutron crystallography; he provided support for Watson, Crick, and Wilkins for their work on unraveling the mysteries of DNA and to Max Perutz for his 1962 Nobel Prize-winning work on the structure of hemoglobin. Here again, we witness the enabling nature of physics—establishing instruments and designing experiments as well as solving mysteries in the biomedical sciences.

Certain other uses for x rays will be studied in later chapters. X rays are useful in the treatment of cancer because of the inhibiting effect they have on cell reproduction. X rays observed coming from outer space are useful in determining the nature of their sources, such as neutron stars and possibly black holes. Created in nuclear bomb explosions, x rays can also be used to detect clandestine atmospheric tests of these weapons. X rays can cause excitations of atoms, which then fluoresce (emitting characteristic EM radiation), making x-ray-induced fluorescence a valuable analytical tool in a range of fields from art to archaeology.

  • X rays are relatively high-frequency EM radiation. They are produced by transitions between inner-shell electron levels, which produce x rays characteristic of the atomic element, or by accelerating electrons.
  • X rays have many uses, including medical diagnostics and x-ray diffraction.

summary of x ray

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x-rays of King George and Queen Mary

As with many of mankind's monumental discoveries, X-ray technology was invented completely by accident. In 1895, a German physicist named Wilhelm Roentgen made the discovery while experimenting with electron beams in a gas discharge tube . Roentgen noticed that a fluorescent screen in his lab started to glow when the electron beam was turned on. This response in itself wasn't so surprising -- fluorescent material normally glows in reaction to electromagnetic radiation -- but Roentgen's tube was surrounded by heavy black cardboard. Roentgen assumed this would have blocked most of the radiation.

Roentgen placed various objects between the tube and the screen, and the screen still glowed. Finally, he put his hand in front of the tube, and saw the silhouette of his bones projected onto the fluorescent screen. Immediately after discovering X-rays themselves, he had discovered their most beneficial application.

Roentgen's remarkable discovery precipitated one of the most important medical advancements in human history. X-ray technology lets doctors see straight through human tissue to examine broken bones, cavities and swallowed objects with extraordinary ease. Modified X-ray procedures can be used to examine softer tissue, such as the lungs , blood vessels or the intestines.

In this article, we'll find out exactly how X-rays machines pull off this incredible trick. As it turns out, the basic process is really very simple.

What's an X-Ray?

The x-ray machine, are x-rays bad for you.

X-rays are basically the same thing as visible light rays. Both are wavelike forms of electromagnetic energy carried by particles called photons (see How Light Works for details). The difference between X-rays and visible light rays is the energy level of the individual photons. This is also expressed as the wavelength of the rays.

Our eyes are sensitive to the particular wavelength of visible light, but not to the shorter wavelength of higher energy X-ray waves or the longer wavelength of the lower energy radio waves .

Visible light photons and X-ray photons are both produced by the movement of electrons in atoms . Electrons occupy different energy levels, or orbitals, around an atom's nucleus. When an electron drops to a lower orbital, it needs to release some energy -- it releases the extra energy in the form of a photon. The energy level of the photon depends on how far the electron dropped between orbitals. (See this page for a detailed description of this process.)

When a photon collides with another atom, the atom may absorb the photon's energy by boosting an electron to a higher level. For this to happen, the energy level of the photon has to match the energy difference between the two electron positions. If not, the photon can't shift electrons between orbitals.

summary of x ray

The atoms that make up your body tissue absorb visible light photons very well. The energy level of the photon fits with various energy differences between electron positions. Radio waves don't have enough energy to move electrons between orbitals in larger atoms, so they pass through most stuff. X-ray photons also pass through most things, but for the opposite reason: They have too much energy.

They can, however, knock an electron away from an atom altogether. Some of the energy from the X-ray photon works to separate the electron from the atom, and the rest sends the electron flying through space. A larger atom is more likely to absorb an X-ray photon in this way, because larger atoms have greater energy differences between orbitals -- the energy level more closely matches the energy of the photon. Smaller atoms, where the electron orbitals are separated by relatively low jumps in energy, are less likely to absorb X-ray photons.

The soft tissue in your body is composed of smaller atoms, and so does not absorb X-ray photons particularly well. The calcium atoms that make up your bones are much larger, so they are better at absorbing X-ray photons .

In the next section, we'll see how X-ray machines put this effect to work.

The most important contributions of X-ray technology have been in the world of medicine, but X-rays have played a crucial role in a number of other areas as well. X-rays have been pivotal in research involving quantum mechanics theory, crystallography and cosmology. In the industrial world, X-ray scanners are often used to detect minute flaws in heavy metal equipment. And X-ray scanners have become standard equipment in airport security, of course.

The heart of an X-ray machine is an electrode pair -- a cathode and an anode -- that sits inside a glass vacuum tube . The cathode is a heated filament , like you might find in an older fluorescent lamp . The machine passes current through the filament, heating it up. The heat sputters electrons off of the filament surface. The positively-charged anode, a flat disc made of tungsten , draws the electrons across the tube.

summary of x ray

The voltage difference between the cathode and anode is extremely high, so the electrons fly through the tube with a great deal of force. When a speeding electron collides with a tungsten atom, it knocks loose an electron in one of the atom's lower orbitals. An electron in a higher orbital immediately falls to the lower energy level, releasing its extra energy in the form of a photon. It's a big drop, so the photon has a high energy level -- it is an X-ray photon.

summary of x ray

Free electrons can also generate photons without hitting an atom. An atom's nucleus may attract a speeding electron just enough to alter its course. Like a comet whipping around the sun , the electron slows down and changes direction as it speeds past the atom. This "braking" action causes the electron to emit excess energy in the form of an X-ray photon.

The high-impact collisions involved in X-ray production generate a lot of heat. A motor rotates the anode to keep it from melting (the electron beam isn't always focused on the same area). A cool oil bath surrounding the envelope also absorbs heat.

The entire mechanism is surrounded by a thick lead shield. This keeps the X-rays from escaping in all directions. A small window in the shield lets some of the X-ray photons escape in a narrow beam. The beam passes through a series of filters on its way to the patient.

A camera on the other side of the patient records the pattern of X-ray light that passes all the way through the patient's body. The X-ray camera uses the same film technology as an ordinary camera , but X-ray light sets off the chemical reaction instead of visible light. (See How Photographic Film Works to learn about this process.)

Generally, doctors keep the film image as a negative . That is, the areas that are exposed to more light appear darker and the areas that are exposed to less light appear lighter. Hard material, such as bone, appears white, and softer material appears black or gray. Doctors can bring different materials into focus by varying the intensity of the X-ray beam.

In a normal X-ray, most soft tissue doesn't show up clearly. To focus in on organs, or to examine the blood vessels that make up the circulatory system, doctors must introduce contrast media into the body, which are are liquids that absorb X-rays more effectively than the surrounding tissue. To bring organs in the digestive and endocrine systems into focus, a patient will swallow a contrast media mixture, typically a barium compound. If the doctors want to examine blood vessels or other elements in the circulatory system, they will inject contrast media into the patient's bloodstream. Contrast media are often used in conjunction with a fluoroscope . In fluoroscopy, the X-rays pass through the body onto a fluorescent screen, creating a moving X-ray image. Doctors may use fluoroscopy to trace the passage of contrast media through the body. Doctors can also record the moving X-ray images on film or video.

X-rays are a wonderful addition to the world of medicine; they let doctors peer inside a patient without any surgery at all. It's much easier and safer to look at a broken bone using X-rays than it is to open a patient up.

But X-rays can also be harmful. In the early days of X-ray science, a lot of doctors would expose patients and themselves to the beams for long periods of time. Eventually, doctors and patients started developing radiation sickness , and the medical community knew something was wrong.

The problem is that X-rays are a form of ionizing radiation . When normal light hits an atom, it can't change the atom in any significant way. But when an X-ray hits an atom, it can knock electrons off the atom to create an ion , an electrically charged atom. Free electrons then collide with other atoms to create more ions.

An ion's electrical charge can lead to unnatural chemical reactions inside cells . Among other things, the charge can break DNA chains. A cell with a broken strand of DNA will either die or the DNA will develop a mutation. If a lot of cells die, the body can develop various diseases. If the DNA mutates, a cell may become cancerous , and this cancer may spread. If the mutation is in a sperm or an egg cell, it may lead to birth defects. Because of all these risks, doctors use X-rays sparingly today.

Even with these risks, X-ray scanning is still a safer option than surgery. X-ray machines are an invaluable tool in medicine, as well as an asset in security and scientific research. They are truly one of the most useful inventions of all time.

For more information on X-rays and X-ray machines, check out the links that follow.

Lots More Information

Related articles.

  • The Ultimate Human Body Quiz
  • How Light Works
  • How Atoms Work
  • How MRI Works
  • How Nuclear Medicine Works
  • How Ultrasound Works
  • Do certain radio wave frequencies pose health risks?
  • How far does ultraviolet light penetrate into the body?

More Great Links

  • X-Rays: Another Form of Light
  • An Inexpensive X-ray Machine
  • The interaction of radiation with matter
  • Generation and Properties of X-rays
  • Overview of X-ray Computed Tomography
  • Radiation expert warns of danger from overuse of medical X-rays

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summary of x ray

by Chris Woodford . Last updated: October 31, 2022.

Photo: Once X rays had to be treated like old-fashioned photographs. Now, they're as easy to study and store as digital photographs on computer screens. Photo by Kasey Zickmund courtesy of U.S. Air Force.

What are X rays?

Artwork: The electromagnetic spectrum, with the X-ray band highlighted in yellow over toward the right. You can see that X rays have shorter wavelengths, higher frequencies, and higher energy than most other types of electromagnetic radiation, and don't penetrate Earth's atmosphere. Their wavelengths are around the same scale as atomic sizes. Artwork courtesy of NASA (please follow this link for a bigger and clearer version of this image).

summary of x ray

Artwork: Lead is a heavy element that you'll find toward the bottom of the periodic table: its atoms contain lots of protons and neutrons, so they're very dense and heavy. Lead is very good at stopping X rays.

What are X rays used for?

Photo: Taking a dental X ray with modern, digital technology. This equipment uses low-power (and therefore safer) X rays and instead of the dentist having to develop an old-fashioned photo, the results show up almost instantly on their computer screen. Photo by Matthew Lotz courtesy of US Air Force .

Photo: A typical CT scanner. The patient lies on the bed, which slides through the hole in the donut-shaped scanner behind. The scanner unit contains one or more rotating X-ray sources and detectors. Photo by Francisco V. Govea II courtesy of US Air Force and Wikimedia Commons .

Photo: Using digital X ray equipment (left) to check the contents of a suspicious package (on the floor, right). Photo by Jonathan Pomeroy courtesy of US Air Force .

Photo: Nondestructive X ray testing is one way to inspect planes without taking them apart. Here, a plane has just been tested in a lead-lined hangar at Randolph US Air Force Base, Texas. The warning signs you can see on the door indicate the potential dangers from the X rays. Photo by Steve Thurow courtesy of US Air Force.

Photo: Studying semiconductor materials with X-ray spectroscopy. Photo by Jim Yost courtesy of US DOE/NREL .

Photo: X-ray image of the Sun produced by the Soft X-ray Telescope (SXT). Photo courtesy of NASA Goddard Space Flight Center (NASA-GSFC) .

How are X rays produced?

How were x rays discovered.

Photo: Wilhelm Röntgen's X-ray photograph of his wife's hand. Note the rings! Photo believed to be in the public domain, courtesy of the National Library of Medicine's Images from the History of Medicine (NLM) collection and the National Institutes of Health .

19th century

20th century.

Illustration: A typical Coolidge tube. Artwork courtesy of the Wellcome Collection published under a Creative Commons (CC BY 4.0) licence .

Photo: The Chandra X-ray telescope just before it was released from the Space Shuttle Columbia on on July 23, 1999. Photo courtesy of NASA/JSC

21st century

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Patient handouts.

X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of your body. The images show the parts of your body in different shades of black and white. This is because different tissues absorb different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white. Fat and other soft tissues absorb less and look gray. Air absorbs the least, so lungs look black.

The most familiar use of x-rays is checking for fractures (broken bones), but x-rays are also used in other ways. For example, chest x-rays can spot pneumonia. Mammograms use x-rays to look for breast cancer.

When you have an x-ray, you may wear a lead apron to protect certain parts of your body. The amount of radiation you get from an x-ray is small. For example, a chest x-ray gives out a radiation dose similar to the amount of radiation you're naturally exposed to from the environment over 10 days.

  • Medical X-Rays (Food and Drug Administration)
  • X-Ray (Mayo Foundation for Medical Education and Research) Also in Spanish
  • Contrast Materials (American College of Radiology; Radiological Society of North America) Also in Spanish
  • How to Read Your Radiology Report (American College of Radiology; Radiological Society of North America) Also in Spanish
  • Products for Security Screening of People (Food and Drug Administration)
  • Radiation Dose from X-Ray and CT Exams (American College of Radiology; Radiological Society of North America) Also in Spanish
  • Tracing the X-Ray Trail (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Abdominal X-Ray (American College of Radiology; Radiological Society of North America) Also in Spanish

From the National Institutes of Health

  • Cystogram (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Discography (Discogram) (American College of Radiology; Radiological Society of North America) Also in Spanish
  • Lower Extremity Radiography (American Society of Radiologic Technologists) - PDF
  • Panoramic Dental X-Ray (American College of Radiology; Radiological Society of North America) Also in Spanish
  • Radiography of the Paranasal Sinuses (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Skull Radiography (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Upper Extremity Radiography (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Venography (American College of Radiology; Radiological Society of North America) Also in Spanish

Journal Articles References and abstracts from MEDLINE/PubMed (National Library of Medicine)

  • Article: POLCOVID: a multicenter multiclass chest X-ray database (Poland, 2020-2021).
  • Article: A Comparison of Radiographic Outcomes after Total Hip Arthroplasty between the...
  • Article: X-ray inhibits FUT4-mediated proliferation in A549 cells by downregulating SP1 expression.
  • X-Rays -- see more articles
  • American College of Radiology Accredited Facility Search (American College of Radiology)
  • Food and Drug Administration
  • RadiologyInfo (American College of Radiology; Radiological Society of North America) Also in Spanish
  • Keeping Kids Still during Exams (American Society of Radiologic Technologists) - PDF - In English and Spanish
  • Pediatric VCUG (Voiding Cystourethrogram) (American College of Radiology; Radiological Society of North America) Also in Spanish
  • X-Ray Exam: Abdomen (For Parents) (Nemours Foundation)
  • X-Ray Exam: Ankle (Nemours Foundation)
  • X-Ray Exam: Bone Age Study (For Parents) (Nemours Foundation) Also in Spanish
  • X-Ray Exam: Cervical Spine (For Parents) (Nemours Foundation)
  • X-Ray Exam: Chest (For Parents) (Nemours Foundation)
  • X-Ray Exam: Elbow (Nemours Foundation)
  • X-Ray Exam: Femur (Upper Leg) (Nemours Foundation)
  • X-Ray Exam: Finger (Nemours Foundation) Also in Spanish
  • X-Ray Exam: Foot (Nemours Foundation)
  • X-Ray Exam: Forearm (Nemours Foundation)
  • X-Ray Exam: Hand (Nemours Foundation)
  • X-Ray Exam: Hip (Nemours Foundation)
  • X-Ray Exam: Knee (Nemours Foundation)
  • X-Ray Exam: Leg Length (Nemours Foundation) Also in Spanish
  • X-Ray Exam: Lower Leg (Tibia and Fibula) (Nemours Foundation) Also in Spanish
  • X-Ray Exam: Neck (Nemours Foundation) Also in Spanish
  • X-Ray Exam: Pelvis (For Parents) (Nemours Foundation)
  • X-Ray Exam: Scoliosis (Nemours Foundation)
  • X-Ray Exam: Upper Arm (Humerus) (Nemours Foundation)
  • X-Ray Exam: Upper Gastrointestinal Tract (Upper GI) (Nemours Foundation)
  • Galactography (Ductography) (American College of Radiology; Radiological Society of North America) Also in Spanish
  • X-Rays, Pregnancy and You (Food and Drug Administration)
  • Barium enema (Medical Encyclopedia) Also in Spanish
  • Bone x-ray (Medical Encyclopedia) Also in Spanish
  • Chest x-ray (Medical Encyclopedia) Also in Spanish
  • Enteroclysis (Medical Encyclopedia) Also in Spanish
  • Lumbosacral spine x-ray (Medical Encyclopedia) Also in Spanish
  • Pelvis x-ray (Medical Encyclopedia) Also in Spanish
  • Skull x-ray (Medical Encyclopedia) Also in Spanish

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1 Production and Properties of X-Rays

In this chapter you will learn about the construction and function of the x-ray tube. A satisfactory understanding of exposure and imaging terms requires at least a limited understanding of x-rays and their properties.

Learning Objectives

At the end of this chapter you should be able to:

  • Name and describe the two parts of the cathode.
  • Describe the appearance of the anode.
  • Explain the purpose of the glass envelope and the tube housing.
  • Draw a diagram of the x-ray tube and label the parts.
  • Explain how the parts of the x-ray tube function to produce x-rays.
  • Place the events involving the production of x-rays in chronological order.
  • Differentiate between the terms anode, target and focal spot.
  • Describe the interactions in the anode and the x-ray energies they produce.
  • Explain these properties of x-rays: divergent rays, photon energy, visibility, speed, ability to produce scatter, effect on phosphors, effect on photodetectors, and the ability to cause biological damage.

X-rays are a form of invisible electromagnetic radiation and were discovered on November 8, 1895 by Wilhelm Conrad Roentgen. Electromagnetic radiation includes visible light as well as other “waves” like microwaves, radio waves and gamma rays. X-rays have similar properties to other types of electromagnetic radiation since they all travel at the same speed and obey many of the same laws. X-rays, however, are distinguished by their extremely short wavelength (about 1/10,000 the length of visible light waves). It is this short wavelength that enables x-rays to penetrate materials that normally absorb or reflect light.

A quick overview of x-Ray Generation

Basically, x-rays are produced when high speed electrons strike matter. This can occur inside or outside a vacuum. Because molecules of air can interfere with the travel of the electrons, creating x-rays in a vacuum is more efficient and effective. Since a vacuum is basically space without any matter in it, we need to contain the components for creating x-rays in something that can keep the air out. The device we use for keeping the air out and maintaining a vacuum for the x-rays to be created in is the x-ray tube.

The modern x-ray tube consists of an evacuated (i.e. enclosing a vacuum) glass or metal bulb into which two electrodes – the cathode and the anode – are sealed. The glass bulbs are similar to an incandescent light bulb in which the filament glows instead of burning out because there is no air to support combustion (See Figure 1-1). In the original incandescent light bulbs, electrons from the electrode wires were connected by cotton filament. This caused the cotton to heat up enough to glow. The only  reason the cotton didn’t burst into flames is because there is no air inside the bulb.

Figure 1-1: The Incandescent Light Bulb compared to a Coolidge X-Ray Tube

summary of x ray

The Coolidge tube is one of the earliest designs of the  x-ray tube.  While the positive and negative electrodes in the light bulb both connect to the bottom of the bulb, the positive (left) and negative (right) electrodes of the x-ray tube are connected at opposite ends of the bulb.

The invention of the Coolidge type of x-ray tube made it possible to maintain a constant source of x-rays that could be easily duplicated at will because it was evacuated. The degree of vacuum of the Coolidge x-ray tube and the arrangement of the electrodes are such that no electricity can travel between the electrodes until the filament in the cathode is heated. The advent of the evacuated x-ray tube was a critical step in the development of diagnostic x-ray as a tool in modern medicine.

X-Ray Tube Construction

The inside of the x-ray tube consists of two main parts: the cathode and the anode. These two parts work together to produce x-rays. Electrons are released from the cathode, they zoom over to the anode, and when they collide with the anode x-rays are produced.

The Cathode

Figure 1-2: The Cathode Assembly of the X-Ray Tube

The cathode (Figure 1-2) is the negatively charged electrode. It consists of two filaments (usually) and a focusing cup.

The Filament

Figure 1-3: The Filament

summary of x ray

This shows a close up of the coiled filament. When the filament is heated, electrons escape from the metal of the filament and produce a cloud of electrons around the filament. (In this chapter, we will illustrate electrons that have escaped from the filament in blue. All other electrons will be shown in yellow.)

The filament’s role in x-ray production is to release electrons. The filament is a tiny wire made of tungsten and shaped into a coil or spiral. It looks a little bit like the spring inside a ball point pen. See Figure 1-3. Tungsten is the preferred filament material due to its ability to resist melting at high temperatures. Pure tungsten or a mixture of tungsten and thorium provide wire filaments with melting points of around 3400 degrees C or 6000 degrees F.When electrons flow through the filament, the filament heats up and some of the electrons are emitted and are then free to cross the x-ray tube. The number of electrons released is controlled by the number of electrons allowed to flow through the filament, which is described in electrical terms as the current or amperage.The higher the current, the higher temperature the filament reaches and the greater the electron emissions.

Key Takeaways

While an x-ray tube can function with one filament, there are usually two filaments. An x-ray tube with two filaments is called a dual-focus x-ray tube, because the selection of the filament controls the focal spot size for the exposure.  The two filaments are positioned next to each other and are parallel to each other. The large filament is longer than the small filament.

The Focusing Cup

Figure 1-4: The Focusing Cup

summary of x ray

The orange structures in the diagram above are the focusing cup. The negative charge on the focusing cup repels the electrons released from the filament making a tighter electron beam.

The focusing cup is a metal device that surrounds the filament. See Figure 1-4. The focusing cup surrounds the filament on three sides. It is the role of the focusing cup to compress the electron beam as it crosses the x-ray tube. The cup is made of nickel and is negatively charged.

Figure 1-5: The Rotating Anode

summary of x ray

The anode is shaped like a saucer. When visualizing how the anode sits in the x-ray tube, think of a saucer standing on end with its bottom facing the filament wires (Figure 1-5). The edge of the anode that tilts back is where the x-rays are produced. The anode rotates while the x-rays are being produced so that the production of x-rays takes place all around the edge of the anode in an area called the focal track . If we took a snapshot of the process of x-ray production, the exact area that the electrons strike along the focal track is called the focal spot or target .

Figure 1-6: Layers of the Anode Disk

summary of x ray

The top layer of the anode is made of tungsten.  The layer of tungsten is bonded to a molybdenum disk. Molybdenum inhibits heat transfer from the surface of the anode to help prevent damage to the rotor. Some anodes are also backed with a layer of graphite.

The modern anode (Figure 1-6), which is the positively charged electrode, is a disk made of molybdenum and coated with tungsten, which has a little rhenium added to it. Tungsten has a high atomic number, which is important for efficient x-ray production, and a high melting point that helps it endure the extreme temperatures that can occur during x-ray production. The rhenium serves to reduce cracks and surface imperfections in the anode disk. The molybdenum prevents the heat produced by the electron interactions from traveling down the stem of the anode and warping the bearings that allow the anode to rotate. Graphite keeps the anode from cracking when it experiences rapid changes in temperature.

The positively charged anode:

  • Accelerates the emitted electrons, AND
  • Stops the accelerated electrons, causing kinetic energy to be converted to x-rays.

The anode has two roles in the production of x-rays. First, the positive charge applied to the anode creates a potential difference, or voltage, that further accelerates the electrons released by the filament. The voltage applied to the x-ray tube during the creation of x-rays is typically between 60,000 and 120,000 volts! This extremely high voltage causes the electrons crossing the tube to reach speeds nearly equal to the speed of light!!!! Newton’s Second Law of Motion tells us that even though an electron has a really small amount of mass, a high rate of acceleration can still cause it to produce a high amount of force, which we typically think of in terms of kinetic energy. This brings us to the second role of the anode – to stop those speeding electrons! When we bring those electrons to a stop, all that extra energy has to go somewhere – The Law of Conservation of Matter and Energy tells us that matter and energy can be neither created nor destroyed, only changed from one form to another. When we stop those speeding electrons we convert the kinetic energy that the electrons had acquired while crossing the x-ray tube into electromagnetic energy – x-rays.

The anode rotates to help spread out the heat created by the electron interactions at the target. The anodes in standard x-ray tubes typically rotate at around 3,000 rpm. For radiographic examinations that require high tube current (lots of electrons hitting the anode) or exams where multiple exposures are made in a very short amount of time (like CT scanners), high speed rotating anodes with rotational speeds of about 10,000 rpm are used.

The Glass Envelope

The inside parts of the x-ray tube (the cathode, containing the filament and focusing cup, and the anode) are surrounded by a glass housing made of Pyrex glass (Figure 1-7). The glass housing has a thin spot in it called the window. This Pyrex glass has lead added to it. The lead helps to absorb any leakage radiation, i.e. radiation that tries to go any direction but through the window.

The x-ray beam is produced at the anode and first exits the tube through this window before it travels toward the patient’s body.While the x-ray tube is being manufactured  it is baked, and this removes the air inside the glass housing, creating a vacuum. As mentioned earlier, the vacuum is important to getting consistent amounts of x-rays produced during the exposure. If the glass envelope cracks, the vacuum is destroyed and it’s time to buy a new x-ray tube.

Figure 1-7: The Modern  Glass Enclosed X-Ray Tube

summary of x ray

Figure 1-8: The X-Ray Tube within its Metal Housing.

The Metal Housing

A metal housing is built on the outside of the glass envelope. One of its purposes is to protect the glass envelope. The metal housing is what the radiographer sees when looking at the x-ray tube. The insides of the tube and the glass envelope are hidden by this metal housing. At first students often confuse the collimator box with the tube. The x-ray tube sits above the collimator box (Figure 1-8).

Production of the X-Ray Beam

Now that we know about the individual components of the x-ray tube and their roles, let’s examine the production of the x-ray beam in a little more detail. X-rays are produced inside the x-ray tube after a chain of events involving the filament, focusing cup and anode. The chain of events involves releasing electrons from atoms at the filament, giving the released electrons a high speed, focusing these electrons, and the stopping them suddenly at the anode where the x-rays are produced (see Figure 1-9).

Figure 1-9: Production of the X-Ray Beam

summary of x ray

Releasing the Electrons

The first event is the removal of electrons from the atoms contained in the filament wire. The filament is the source of the electrons. The filament wires are connected in a circuit, which is a group of wires that can conduct electricity. The circuit containing the filament wires is called the filament circuit. The number of electrons flowing in a circuit is described by the term current . When current is sent through this circuit, one of the two filament wires heats up. The more electrons that flow through the filament, the hotter the filament wires get.

The filament wires are made of tungsten, which has a high melting point. The high melting point is important because the current causes the wire to get hot enough to actually glow. This glowing is called incandescence . When the filament gets this hot, electrons are “boiled off” or freed from the atoms of the filament. This process of releasing electrons is called thermionic emission – “therm-” meaning heat and “-ionic” meaning a charged particle, in this case an electron. Because the temperatures necessary for thermionic emission in tungsten are very near its melting point, reaching thermionic emission can put us at risk of melting the filament wire, resulting in catastrophic failure of the x-ray tube. To help reduce the risk of melting the filament wires, we can add a little bit of thorium to the tungsten. The thorium causes thermionic emission to take place at significantly lower temperatures and keeps us from reaching the melting point of tungsten under normal circumstances.

Figure 1-10: Electron Cloud or Space Charge

summary of x ray

For a fraction of a second these electrons sit right beyond the filament in a group called the electron cloud or space charge (Figure 1-10). All electrons are negatively charged, and since like charges repel each other, the electrons in this group want to spread out away from each other. So, the focusing cup is used to hold the group of electrons together.

Focusing the Electrons

The focusing cup helps the electrons hit the anode in a small area.

The focusing cup surrounds the filament on three sides. It is the role of the focusing cup to compress the electron beam as it crosses the x-ray tube. See Figure 1-11. The cup is made of nickel and is negatively charged. Because like charges repel each other, the negative charge on the focusing cup repels the electrons that are emitted from the filament, keeping them from spreading out across the x-ray tube. The repulsive action of the focusing cup also serves to propel the stream of electrons away from the cathode and toward the focal spot on the anode.

Figure 1-11: Focusing the Electron Cloud

summary of x ray

Accelerating the Electrons to High Speed

The electrons must travel from the cathode to the anode at high speeds to produce x-rays. Two forces work together to produce this high speed. During the exposure, the focusing cup gets a strong negative charge and the anode gets a strong positive charge. The negatively charged electrons sitting in their group (the space charge) just beyond the filament are repelled by the negatively charged focusing cup. This causes the electrons to leave the filament as a group and shoot over to the anode. While the negative charge of the focusing cup starts the electron stream moving, the pull of the anode is primarily responsible for the high speeds the electrons reach (Figure 1-11).

The high kilovoltage (thousands of volts) applied to the x-ray tube causes the anode to have a very high positive charge. Because the anode has this high positive charged, and opposite charges attract, the positive anode pulls the negative electrons from the filament at the same time that they are being repelled by the focusing cup. This combination of push and pull forces the electrons to travel at high speed between the filament and the anode. The high speed gives the electrons a large amount of kinetic energy, which is the energy of motion.

Stopping the Electrons and Creating X-rays

The actual place that the electrons hit on the surface of the anode is called the target . The anode disk is made of molybdenum, which is coated with tungsten so the anode surface or the target area is made of tungsten. The size of the area that the electrons hit is called the focal spot (Figure 1-11). The anode disk, the target and the focal spot are all physically located in the same place (at the anode), but the terms should not be interchanged since they each mean something different.

Figure 1-12: Isotropic Emission of X-Rays

summary of x ray

X-rays are emitted from the focal spot in all directions. This is called isotropic emission. The tube housing absorbs the radiation that is directed at any angle other than through the window.

When the x-rays are produced at the focal spot, they fly off in all directions, like the sparks from a Fourth of July sparkler.  This spherical pattern is called isotropic emission (Figure 1-12). Only the x-rays that are aimed at the patient are useful to us. The rest of the x-rays could fly out of the tube and hit people other than the patient. This is why a lead glass envelope and a lead-lined metal housing are put around the cathode and anode. These housings and the anode disk absorb this unnecessary radiation. A tiny bit of radiation still might get through, and this is called leakage radiation. Leakage radiation is limited to no more than 100mR/hour at 1 meter.

Activity 1A – X-Ray Components Crossword

Use this crossword puzzle to test your knowledge of the components of the x-ray tube.

Activity 1B – The Process of X-Ray Production

Place the steps in the production of x-rays in the correct order.

Electron Interactions with Target Atoms

The wavelengths and energy levels of the x-rays in the beam are determined by the specific interactions of the electrons with the atoms in the anode. Atoms with a high atomic number will have much larger nuclei and a LOT more orbital electrons with which the high-speed electrons from the cathode may interact. Because there is more for the high-speed electrons, i.e. incident electrons, to interact with, a lot more interactions occur and those that do occur will result in the production of higher energy x-rays. This is the primary reason Tungsten (atomic number 74) is chosen as the target material on the anode.

When the electrons slam into the anode at high speed, they interact in one of three locations: with an outer shell orbital electron, with an inner shell orbital electron, or with the nucleus.  What gets created depends on where the incident electron interacts.

Outer Shell Interactions

When the incident electron (i.e. an incoming electron or electrons emitted at the filament) interacts with an outer shell electron, energy is transferred from the high-speed electron that causes the outer shell electron to become excited. When the outer shell electron absorbs more energy that the binding energy that keeps it in its orbital, it jumps up to the next higher electron shell. However, it leaves a vacancy in its normal orbital. To return to its normal orbital, the excited electron releases the excess energy in the form of infrared radiation – heat.  99% of all incident electron interactions create heat.

Electron interactions with outer shell orbital electrons in the target create heat.

While we don’t typically think of heat as similar to light, infrared radiation is actually part of the electromagnetic spectrum. It just has a much longer wavelength and a much lower energy than x-rays.

Inner Shell Interactions

Some incident electrons make it past the outer shell and interact with inner shell electrons. To understand these interactions that occur between the incident electrons and inner shell electrons of the target atoms, we need to understand electron binding energies – the energy that keeps the electrons in place around an atom.

Electron Binding Energy

We know that electrons are contained in orbitals or shell in organized levels around the nucleus. Because the nucleus has a positive charge and electrons are negative, there is a force attracting the electrons toward the nucleus. We call this attractive force electron binding energy because it binds the electrons in place – keeping them in their orbital shells.

The electron binding energy on a particular electron is dependent on two factors: how many protons are in the nucleus and how far the orbital electron is from the nucleus. The number of protons in the nucleus is an important piece of information about an atom because it determines the chemical properties of the element and its place in the periodic table. This means that the electron binding energies are different for atoms of each different element. The orbital electron’s distance from the nucleus is defined by its orbital shell. When physicists talk about the electron shells, they label them with letters, starting with the letter K. The reason orbitals start with the letter K and not A has a humorous story behind it. Physicist Charles G. Barkla was one of the early scientists studying x-ray production. He had noticed that there were two different energy levels of x-rays emitted from the atoms struck with high speed electrons. He started off talking about the x-rays with the highest energies as type A x-rays and the lower energy x-rays as types B, C, etc., but he wasn’t sure that the type A x-rays were the highest energy x-rays possible. Since he wanted to leave room in his labeling scheme for the discovery of even higher energy x-rays, he changed the name of the highest energy x-rays he had identified to type K. It turns out that k-type x-rays were the highest energy x-rays possible with this type of interaction, but by that time the name had stuck. So the highest energy x-rays are called K x-rays and the electron shell that the x-rays are emitted from, which happens to be the electron shell closest to the nucleus is called the K-shell. See Figure 1-13 for a Bohr model of a tungsten atom with labeled shells.

Figure 1-13: Bohr Model of a Tungsten Atom

summary of x ray

Tungsten has an atomic number of 74 and is surrounded by 74 electrons. The shells are labeled starting at K from the inside out.

In the interaction between an incident electron and an inner shell electron, the high-speed electron passes near an inner shell orbital electron. Because both electrons have a negative charge and like charges repel, the repulsive force between the two electrons ejects the orbital electron from its orbit. This leaves a vacancy in the inner orbital, which makes the atom unstable. In order to become more stable one of the outer shell electrons drops into the inner shell to fill the vacancy. Because outer shell electrons have more energy to fight the attractive force of the positive nucleus, the outer shell electron has to lose energy to move into the inner shell vacancy. The energy that the outer shell electron loses is released as an x-ray. We call this x-ray characteristic radiation because the energy of the emitted x-ray is characteristic of the difference between the binding energies of the shell the orbital electron came from and the shell it dropped into (see Figure 1-13).

Figure 1-13: Characteristic Interactions

summary of x ray

Characteristic interactions happen in 2 steps. In the first, the incident electron from the filament interacts with an inner shell electron, ejecting it from its orbit. In the second step, an outer shell electron loses energy in the form of a characteristic x-ray so that it can drop into the inner shell vacancy.

Characteristic radiation makes up a small portion, less than 15%, of the total x-ray beam. Characteristic x-rays are completely dependent on the difference in energy levels between the orbits in the atom. Since the binding energies for each orbital level are known for each element, we can accurately calculate the energy of each characteristic x-ray produced. For tungsten atoms, the innermost orbital electrons have a binding energy of 69.5 keV. Since the more distant orbitals have binding energies ranging from 0.5 to 12 keV, we can expect all characteristic x-rays produced in a tungsten target to have energies between 57.5 and 69 keV.

If we graph the number of characteristic x-ray photons at each energy level, we will see a series of vertical lines. These lines will be clustered into two groups, one for x-rays released by electrons filling L-shell vacancies and another for x-ray released by electrons filling K-shell vacancies (See Figure 1-14). We call graphs of the number of photons at each energy level emissions spectra . When referring to the shape of the emissions spectra created by characteristic x-rays, we use the term “discrete” because each spike stands separately from the next one. While we can get characteristic interactions occurring when vacancies are filled further from the nucleus, the energy is so low that the photons released are ultraviolet light rather than x-rays.

Figure 1-14: Characteristic X-Ray Emission Spectra

summary of x ray

This graph of the characteristic x-ray energies separates the individual energy spikes. When measuring the actual x-ray output, it can become difficult to distinguish between very closely placed energy spikes. Some emission spectra will illustrate single spikes.

Interactions with the Nucleus

If the high-energy electron passes near the atomic nucleus of the target atom, the positive attraction of the nucleus will cause the electron to slow down or brake (See Figure 1-15). As Roentgen discovered and characterized x-rays in Germany, he applied a German term to this interaction – Bremsstrahlung. Bremsstrahlung means braking in German. When the electron slows down, it is, in essence, losing kinetic energy. We know that the lost energy does not simply disappear, it has to be converted to something else. In this instance the kinetic energy lost by the electron is released as an x-ray photon. Bremsstrahlung radiation accounts for more than 85% of the total number of x-rays in the beam.

Figure 1-15: Bremsstrahlung Interactions

summary of x ray

Projectile electrons that slow down a lot make sharper turns and lose more energy. Projectile electrons that only slow down a little don’t change direction as much and lose less energy.

Because the incident electrons can pass the nucleus at different distances, the amount of deceleration varies. The closer an electron passes to the nucleus, the greater its deceleration will be. Because Bremsstrahlung interactions take place at these different distances, it is these interactions that are responsible for the heterogeneous or poly-energetic nature of the x-ray beam. A heterogeneous x-ray beam is necessary because it is what makes differential absorption possible. In differential absorption, tissues that are more dense or have higher atomic numbers will absorb more x-rays than tissues that are thinner or made of lower atomic number atoms. If all of the x-rays in the beam were the same energy, the radiograph would not show different shades of gray. It would only show black or white. More on this in Chapter 2. A wide variety of x-ray energies are essential to properly demonstrating the subtle differences in tissues.

The distance the electron will pass from the nucleus is a function of statistical probability. We know that the incident electron is more likely to pass through an atom further away from the nucleus and less likely to pass near it. Because electrons passing further from the nucleus do not slow down very much, they emit lower energy x-rays. As the electrons pass closer to the nucleus the energies of the emitted x-rays increases. The probabilities tell us that more low energy x-rays will be produced than high energy ones. Plotting the relationship between the photon energy levels and number of x-ray photons produced at that energy will produce a bell-shaped curve with the greatest number of photons occurring at approximately 1/3 of the highest energy level (See figure 1-16). Notice that all possible energy levels are represented on the bremsstrahlung emissions spectra. We call this type of graph continuous , because there are no breaks in the possible energies of the photons. The highest energy on the bremsstrahlung graph is determined by the kilovoltage selected by the radiologic technologist. For example, if a technologist selects 120 kVp for a PA chest x-ray, the highest possible energy of any bremsstrahlung x-ray will be 120 keV.

Figure 1-16: Bremsstrahlung Emission Spectra

summary of x ray

Bremsstrahlung x-rays have continuously variable energies with the greatest amplitude occurring at approximately 1/3 of the kVp used to create the beam.

Emissions Spectra of the entire Beam

When we combine the graph of the Characteristic radiation energies with the graph of the Bremsstrahlung radiation energies, we get a complete picture of both the number and energies of the x-rays in the beam (Figure 1-17). The amplitude of the bell-shaped brems curve gives us an idea of the total number of x-rays in the x-ray beam. The position of the characteristic spikes indicate the material the anode target is made of. The left-to-right position of the brems curve indicates the median energy of x-ray photons in the beam.

Figure 1-17: The Complete Emission Spectra

summary of x ray

The number of characteristic x-rays gets added to the number of bremsstrahlung x-rays emitted at the same energy level.

Activity 1C – Match the Diagrams

Match each diagram with its description.

Properties of X-rays

After the x-rays are produced they have some properties that are important to understand because the properties affect the quality of the radiograph. The properties also help determine what technical factors the radiographer should use to produce a good radiograph. The properties that are listed in this book are not all the x-ray properties, but they are the ones that pertain to radiographic quality.

X-Ray Property

That x-rays travel in straight lines is a principle quality that we use in the design of our rooms and radiation protection practices. We can be assured that we are safe behind the control panel of our x-ray rooms, even with an open doorway next to us as long as there is no direct line between the radiation source and us. The x-rays cannot turn corners. From the standpoint of image quality, the fact that x-rays only travel in straight lines is what enables us to produce an image that accurately represents the patient’s body.

The part of the x-ray beam that is directed at the patient is only a section of the x-rays produced at the anode (Figure 1-18). Since the remainder of the x-rays are absorbed by the anode, the glass envelope and the tube housing, they are virtually eliminated. The x-rays that are aimed at the patient are still moving away from the focal spot. They all keep traveling in straight lines, but because they are still moving isotropically , they diverge or move away from each other, creating a cone-shaped beam.

Figure 1-18: Diverging Photons Create a Cone-Shaped Beam

summary of x ray

The x-ray beam that is directed at the patient consists of millions of x-rays or what are better called x-ray photons. A photon is a tiny particle of energy. The energy of each of the photons in the x-ray beam can be different. The technical term for this is heterogeneous or polyenergetic .

Figure 1-19: The Heterogenous Beam

summary of x ray

Photons with less energy are absorbed more easily by the patient’s body parts, whereas photons with more energy will penetrate right through the patient’s body. The photons that get through the patient’s body will hit the image receptor and eventually produce an image of the patient’s body.

X-rays are a form of electromagnetic radiation. There are many different kinds of electromagnetic radiation, such as radio waves and light waves, but x-rays are a type that is able to penetrate through matter such as the patient’s body.

Since x-rays are a type of energy, they are invisible. This can make them seem mysterious and is why many people are afraid of them. X-rays cannot be seen as they are produced, as they leave the x-ray tube, or as they enter the patient’s body. It’s obvious that they were there, though, when the image of the patient’s body appears on the radiograph.

The speed of light is 3 x 10 8 meters/second or approximately 186,000 miles/second, and x-rays travel at the same speed as light. The walls in an x-ray room are lined with lead, which is good at absorbing x-rays. The radiographer stands in a lead-shielded area when making the exposure, and since x-rays travel so fast, they will already be absorbed by the lead in the walls by the time the radiographer lets go of the exposure button and gets back inside the x-ray room.

Scattered radiation is produced when x-rays enter the patient’s body. The x-ray beam that is directed at the patient’s body is called the primary beam (Figure 1-20). When the primary beam enters the patient’s body, three things could happen to the photons:

  • Photons could be absorbed by the patient’s body parts.
  • Photons could pass right through the patient’s body and enter the image receptor, depositing energy to create the image. These photons are called exit radiation or remnant radiation .
  • Photons could hit something in the patient’s body, bounce off, and fly out in a new direction. These photons are called scattered radiation .

Figure 1-20: Primary, Remnant and Scattered Radiation

summary of x ray

Scattered radiation that hits the image receptor creates several significant problems for the quality of the radiographic image. Scatter reduces radiographic contrast. Loss of contrast is not good, and there are a variety of things the radiographer can do to avoid the problems associated with scatter. We will examine ways to counteract the effects of scatter radiation in future chapters.

X-rays produce an image of the patient’s body by affecting the image receptor. When x-ray photons hit the image receptor, they interact with the atoms in the receptor and knock some electrons out of place. The removal of an electron from a neutral atom creates an ion pair – a positively charged atom and a negatively charged electron. The process of creating this ion pair is called ionization.

Ionization is a key factor in the creation of the radiographic image. The ionization that takes place in the image receptor produces electrical pulses that are measured to determine the amount of remnant radiation interacting with a specific location within the image receptor. The computer then assigns a shade of gray to that portion of the image based on the level of ionization that occurred there. Areas of the image receptor that absorbed a lot of radiation will have a higher electric charge and will be displayed as darker or black areas on the image. Areas of the image receptor that receive low levels of x-rays will have low electric charges and will be displayed as brighter or white areas on the image. The variation in levels of brightness seen on the radiograph is called contrast.

X-rays can cause certain materials called phosphors to glow or light up. This glowing is called fluorescence. The phosphors light up in proportion to the amount of radiation that hits them. If a large quantity of radiation hits a phosphor, that phosphor lights up very bright. If only a little radiation hits the phosphor, the phosphor gives off only a little light. Fluorescent materials can be used to magnify the action of x-rays in the creation of the radiographic image.

When x-rays interact with a fluorescent phosphor, the phosphor crystals glow. The light given off by the phosphor crystals can cause other materials to release electrons. Because each x-ray can cause the phosphor to release many light photons, a greater electric charge can be produced

The x-ray properties we have been discussing so far are all fascinating and exciting! This last one isn’t so great for us or the patients. X-rays can damage biological or living matter. X-ray photons can change the atoms in the living body to leave some of the atoms in the body. Remember that this process of removing an electron from an atom is called ionization. When ionization happens inside living tissues, the chemical changes that occur can damage the DNA in the cells. This can cause the cell to either die or malfunction. If DNA damage occurs in sperm or ova that are then used to produce a baby, the damage can be transferred to the baby’s body. This is why radiographers must be so careful about protecting themselves, their patients, and others from unnecessary radiation.

  • X-rays travel in straight lines.
  • X-rays diverge from their point of origin at the focal spot.
  • X-ray photons have many different energies.
  • X-rays are highly penetrating.
  • X-rays are invisible.
  • X-rays travel at the speed of light.
  • X-rays produce scattered radiation.
  • X-rays ionize matter.
  • X-rays cause fluorescence of some materials.
  • X-rays cause biological damage.

In addition to the 10 properties listed above, x-rays have other properties that do not have an impact on radiographic image quality. These include:

  • X-rays have no mass.
  • X-rays have no charge. They cannot be deflected by electric or magnetic fields.
  • X-rays cannot be focused with a lens.
  • The are capable of traveling in a vacuum. (Which is a good thing since we are creating them in a vacuum!)

Activity 1D – X-Ray Properties Word Find

Decide which word best matches the definition or completes the sentence, then find it in the word search puzzle and circle it.

  • Can you see x-rays? They are __________
  • One word meaning many energies
  • Another word meaning many energies
  • ____________ radiation is directed at the patient.
  • X-rays travel at the speed of __________.
  • Low energy x-rays are more easily ____________ by the patient’s body.
  • X-rays are highly ______________.
  • X-rays are emitted in all directions. This is called ______________ emission.
  • X-rays __________ from the focal spot.
  • X-rays cause _______________ damage.
  • X-rays are a form of _____________________ radiation.
  • The process of removing electrons from atoms.
  • This type of radiation gets through the patient and deposits energy in the image receptor.
  • X-rays travel in ______________ lines.
  • X-rays cause __________________ of some materials.
  • X-rays that bounce off the patient’s body are called __________

The inside parts of the x-ray tube are the anode and the cathode. The cathode consists of the focusing cup and filament. When x-rays are produced, electrons are released from the filament, given a high speed, and focused into a small group by the focusing cup. When they zoom over to the anode, they are stopped suddenly. The kinetic energy of the electrons is converted to x-rays. X-rays are created by two different types of interactions with target atoms. When the incident electron ejects an inner-shell electron and an outer-shell electron drops in to fill the vacancy, a characteristic x-ray is released. Characteristic x-rays have discrete energies and are graphed as vertical lines. When the incident electron passes the nucleus of the target atom and changes direction because of the attractive pull of the nucleus, the incident electron loses energy in the form of a bremsstrahlung x-ray. Bremsstrahlung x-rays have continuous energy ranges and are graphed as a bell-shaped curve.  X-rays have certain properties. These properties are summarized in Table 1-1.

Kilovoltage peak; determines the energy and penetrating ability of the x-ray beam

The weighted combination of all of the visually significant characteristics of an image that contribute to the diagnostic value of the image.

The sharpness of the lines of the structures included in the image. Recorded detail is related to the concept of spatial resolution.

Digital Radiographic Exposure: Principles & Practice Copyright © 2022 by Carla M. Allen. All Rights Reserved.

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StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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StatPearls [Internet].

X-ray production.

Dawood Tafti ; Christopher V. Maani .

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Last Update: July 31, 2023 .

  • Definition/Introduction

X-rays are a form of electromagnetic radiation with wavelengths ranging from 0.01 to 10 nanometers. In the setting of diagnostic radiology, X-rays have long enjoyed use in the imaging of body tissues and aid in the diagnosis of disease. Simply understood, the generation of X-rays occurs when electrons are accelerated under a potential difference and turned into electromagnetic radiation. [1] An X-ray tube, with its respective components placed in a vacuum, and a generator, make up the basic components of X-ray production. Essential components of an X-ray tube include a cathode, and an anode separated a short distance from each other, a vacuum enclosure, and high voltage cables forming the X-ray generator attached to the cathode and anode components. [2]  In the generation of X-ray production, a cathode filament machined in a cathode cup is activated, causing intense heating of the cathode filament. [3] The heating of the filament leads to the release of electrons in a process called thermionic emission. [4] The released electrons form in an electron cloud at the filament surface, and repulsion forces prevent the ejection of electrons from this negatively charged cloud. [2]  Upon application of a high voltage by an X-ray generator to the cathode as well as the anode, there is an acceleration of electrons ejected to an electrically positive anode. [3]  The filament and the focusing cup determine this path of acceleration. The number of electrons is measured in the form of milliampere (mA) units, where 1 milliampere is equal to 6.24 x 10^15 electrons/s. Electron kinetic energy (measured in keV) is related to the applied voltage. The tube voltage, tube current, and exposure duration (measured in seconds) are adjustable by the user.

Once the high kinetic energy electrons finally reach the anode target, this initiates the process of X-ray production. Tungsten is often the usual anode target, although other material targets are also employed. Electrons come extremely close to the nucleus of the target, causing a deceleration and change in direction, converting the kinetic energy to electromagnetic radiation in a process known as “breaking radiation” or bremsstrahlung. [5] The output is a spectrum of X-ray energies. Incident electrons can also result in ionization, whereby the approaching electron can remove a second electron belonging to an atom of the anode target, losing its energy through ionization or excitation. This process leads to an emission of a photon as the electron orbit vacancy gets filled by an orbital shell electron from a further out shell. Considering orbital energies and their differences are unique in atoms, this leads to a “characteristic X-ray” with energies that can serve as a fingerprint unique to each anode target. Bremsstrahlung X-rays, however, constitute the majority of X-rays produced in this process. 

Before understanding the final production of an X-ray image, it is essential to understand the interaction of X-rays with individuals exposed to X-rays. There are three important types of interactions that occur between X-rays and the tissues of our body. The “classical” or “coherent” interaction occurs when an X-ray strikes an orbital electron and subsequently bounces off and changes direction. [6]  These X-rays are low energy and do not cause ionization and only add a small dose amount to a patient. In “Compton” scattering, X-rays of higher energy strike an outer shell electron and are strong enough to remove it from the shell, causing ionization of an atom. [7] This phenomenon contributes to dose and also contributes to scatter. Photoelectric interactions occur when an incoming X-ray strikes an inner shell electron, removing it from the shell and causing a downward cascade of outer shell electrons filling inner orbit vacancies, further releasing secondary X-rays. This type of interaction contributes to image contrast. Finally, the differential absorption of X-rays within the tissues of the body subsequently contributes to the production of the final image. Attenuation of X-rays ultimately depends on the effective atomic number in tissue, X-ray beam energy, and tissue density. [8]

Image detectors come in the form of digital and analog film detectors. [9] One limitation of analog systems is the limited range of exposure intensities that it can accurately detect; this lends itself to multiple images taken for an adequate and interpretable study, and therefore subsequently leads to increased radiation exposure to a patient. Digital systems allow a user to fix contrast and brightness and provide greater post image processing options. [9]

  • Issues of Concern

Effective dose refers to the amount of radiation received by the whole body, and measurement is in millisievert (mSv). Generally speaking, various procedures entail different effective radiation doses based on site and use of contrast. For example, a radiograph of the spine has an approximate effective dose of around 1 mSv. [10] A radiograph of the extremity ranges within the upper limits of normal between 0.17 to 2.7 microSv. [10] To better place these doses in context, we can compare these exposures with natural radiation we obtain from our surroundings, which usually approximates to 3 mSv per year. [11] A spine X-ray, therefore, is comparable to the natural background radiation exposure for six months. An extremity radiograph compares to natural background radiation exposure of 3 hours. Bone densitometry and mammography studies have an approximate effective dose of around 0.001 mSv and 0.4 mSv, respectively, comparable to 3 hours and six weeks of background radiation, respectively. [12] Radiography, therefore, in the setting of cumulative exposure is not without risks in patients who require frequent imaging studies. An X-ray technician plays an instrumental role in the acquisition of interpretable and high-quality X-ray images. A working and constant relationship between a radiologist and an X-ray technician is essential in troubleshooting and acquiring images in the appropriate diagnosis of a patient. X-ray technicians are also critical in preventing artifacts, taking brief medical histories, ensuring appropriate laterality, appropriate positioning, and adjusting and maintaining various equipment involved in X-ray acquisition.

  • Clinical Significance

Although adequate coverage of the full range of uses of conventional radiographs cannot is beyond the scope of this article, the use of radiography frequently plays a critical role in assessing the various osseous structures of the body. Evaluation of the lungs is also possible, and the use of contrast can also help to examine soft tissue organs of the body, including the gastrointestinal tract and the uterus, such as in the setting of hysterosalpingography. Radiography is useful in performing various procedures including catheter angiography, stereotactic breast biopsies as well as an intra-articular steroid injection. Radiography helps in the evaluation of multiple pathologies, including fractures, types of pneumonia, malignancies, as well as congenital anatomic abnormalities.

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X-ray generator. Contributed by Dawood Tafti, MD

Disclosure: Dawood Tafti declares no relevant financial relationships with ineligible companies.

Disclosure: Christopher Maani declares no relevant financial relationships with ineligible companies.

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X-Ray Interactions, Illustrated Summary (Photoelectric, Compton, Coherent) for Radiologic Technologists and Radiographers

The x-ray interactions are Photoelectric, Compton and Coherent. Photoelectric is mainly responsible for image contrast, Compton contributes to artifacts in the images, and Coherent scattering has little influence in most diagnostic (x-ray/CT) procedures.

Coherent (Classical) Scatter

Overview of the physics behind x-ray interactions.

When x-rays interact with the human body during an x-ray exposure, they form an image that is highly dependent on the type of interactions of matter and x-rays. Diagnostic x-ray interactions are dominated by two different physical interactions – the photoelectric effect and Compton scatter.

Understanding the impact of the photoelectric effect and Compton scatter and their behavior as a function of energy can greatly improve your ability to select the best technical parameters for a given clinical situation.

We start with a high level summary graphic that demonstrates the differences between the x-ray interactions of: photoelectric, compton and coherent scattering and then go into detail on each of the interactions.

The Photoelectric Effect

The photoelectric effect is the dominant contributor to the generation of signal in an x-ray image as the x-ray is coming in and will be stopped and deposit its energy locally.

The photoelectric effect occurs when an x-ray interacts with an electron in the matter. The photo is completely absorbed and its energy is transferred to an electron that is removed from the electron cloud.

Since the electrons that are in the inner shells are at a more stable configuration the electrons in the outer shells will transition to an inner shell and a characteristic x-ray will be emitted. These secondary events are very low energy and are absorbed relatively locally and do not contribute to the measured image signal.

The likelihood of such interactions with inner shells depends strongly on atomic number Z (i.e. Z 3 ), or how many protons are in nucleus.

Therefore, image contrast in x-ray and CT is much better for materials with high Z elements.

During this interaction, electrons which move to the inner shell, preserve energy and emit secondary x-ray photon.

Another important point is that the likelihood of interaction is much higher for lower diagnostic x-ray energies, i.e. ( 1 /E 3 ), where E is the energy of the x-ray photons.

Therefore, when possible it is typically beneficial to use lower energy photons for a given imaging task, provided that they can penetrate the patient.

Rad Take-home Point : In the photoelectric effect an x-ray comes in and deposits its energy locally mostly in an energetic electron (which then deposits its energy locally).

Compton Scattering

Compton Scattering is the second dominant effect in x-ray imaging. In this case, the x-ray photon interacts with an electron in the outer shell, and hence the likelihood of Compton Scattering doesn’t depend on Z.

As shown in the Figure the X-Ray photon knocks the electron out. Then the photon goes out in an opposing direction from the knocked out electron in order to conserve momentum.

It is important to remember here is that unlike in the photoelectric effect, the energy is not all deposited locally.

The scattered photon may still have a significant fraction of the energy of the incoming photon. It can still travel through the patient and potentially could have a secondary scatter effect or could get measured on the detector.

For more information on the impact of x-ray scatter on image quality and the effect of technical parameters on x-ray scatter please see our post on  x-ray scatter .

Rad Take-home Point : In the Compton effect an x-ray interacts with a weakly bound electron and the electron and photon both continue on in opposing directions. 

Coherent Scattering, it is one of the 3 interactions that can take place with diagnostic X-rays and the body. It also has other names ‘Elastic Scattering’ and ‘Rayleigh Scattering’.

Coherent Scattering happens when an X-Ray photon comes in, interacts with electron cloud and goes out. The X-Ray is scattered after this interaction but it has the same energy as it leaves.

If you imagine a rubber band ball and throw it against the wall, it will come off with approximately the same energy it had going in. That’s what we call elastic scattering. That’s why this interaction is called ‘Elastic Scattering’. For diagnostic imaging Coherent scattering only occurs at energies below 10keV.

For a lot of energy spectra used in diagnostic imaging; there are not very many photons below 10keV that pass through the pre-patient attenuators. Therefore,this effect is less relevant that Compton and Photoelectric Effect for diagnostic imaging.

For completeness we will mention that the likelihood is dependent on the number of protons (i.e. Z). So, if you have more protons, you’re more likely to have coherent scattering and it’s inversely proportional to 1 over Energy squared.

As the energy increases of the X-rays this effect is less likely. This is why there is not a big effect for most diagnostic X-ray exams.

Rad Take-home Point :

  • Rad Take Home Point: Coherent scattering is an additional interaction to Compton Scattering and Photoelectric.
  • It only occurs at very low energies. So, it’s not as important as the other two.

Energy Dependence of Interactions

In different parts of the body and at the different energy levels, photoelectric effect and Compton scattering have different contributions.

From the perspective of an image scientist or medical physicist the human body can usually be approximated as a bag of water for the soft tissue and with some bone distributed throughout.

The photoelectric and Compton effects have similar behavior as a function of energy but the energy where the transition occurs between photoelectric being dominant to Compton being dominant is at a higher energy in the case of bones.

In water photoelectric is dominant up to level of 26 keV, while in bones, it is dominant up to 45 keV. Beyond those transition points Compton scatter occurs more often than photoelectric.

As discussed above the likelihood of photoelectric interactions is proportional to Z 3 . This is what is driving the dominance of the photoelectric up to higher energies as the bones contain Ca and other high Z elements.

Rad Take-home Point : Photo-electric effect is dominant at low energies and for high Z materials the transition energy where Compton becomes dominant is significantly higher. 

The regions in an x-ray image with the most attenuation are typically shown as bright in an x-ray image. These regions attenuate or absorb the x-rays at a higher rate than other regions.

The primary interactions dominating diagnostic x-ray imaging are the photoelectric effect and Compton Scattering.

In general, maximizing the contribution of photoelectric interactions will lead to the highest image contrast. This can be achieved by using high Z materials as contrast agents and/or using lower energy x-rays where the photoelectric effect becomes more likely.

To conclude this post we provide a summary table so you have a study guide with all of the information just in one place.

Coherent Scattering:  In a coherent scattering event you have a diagnostic X-ray come in and then the X-ray goes out with a different angle but the same energy.

Photoelectric Effect:  The diagnostic X-ray comes in and then that X-ray is stopped locally and an electron and a characteristic lower energy photon are emitted. Those both deposit their energy relatively locally .

Compton Effect:  Compton is somehow in between Coherent Scattering and the photoelectric effect. The X-ray comes in, it’s scattered and an electron is scattered as well. The electron deposits its energy locally. So, for Compton you’ll have some energy going forward and some energy being deposited.

Dominant Interactions:  Photoelectric and Compton are the dominant interactions. Coherent scattering really only plays impact at really low energies.

Outcome  of photoelectric is that, that photon stopped and that energy is deposited locally. So, if we think of that from a dose perspective or from an imaging perspective, this is how contrast is generated on images. In terms of the Compton scattering, you have some energy deposited locally while the x-ray is changing its direction. So, some energy is going to keep going as the X-ray continues to traverse the matter.

Energy Summary:  Less than 10keV for Coherent scattering and then depending on the material type, around 30keV is the transition between Photoelectric and Compton being dominant. So Photoelectric is dominant at lower energies and Compton is dominant at higher energies. Depending upon what the energy spectrum either photoelectric or Compton will be dominant.If the spectral has a lot of low energy photons, it’s going to be dominated by the Photoelectric effect.

Z-Dependence:  The Z dependence is directly dependent on Z for coherent scattering. For photoelectric, it’s dependent on Z^3, so it’s very strongly dependent on Z. That’s why images of bone are exquisite on X-ray imaging because bones have relatively higher Z.

Compton scattering, Compton is independent of Z.

Impact on Image Contrast:  Coherent scattering, does not a significant impact on an X-ray image. Especially with a standard diagnostic energy spectrum. Photoelectric, is the primary contrast source in your image. Compton scattering leads to a background haze in an X-ray image. It can lead to different more structured artifacts in a CT image.

Impact on Dose: Coherent scattering does not have a significant impact on patient dose.

Impact on Patient Dose:  The electrons deposit the energy locally. So, both Photoelectric and Compton scattering lead to significant contribution there in terms of Patient dose.

Impact on Staff:  Coherent and photoelectric are not significant. Compton scattering on the other hand is the dominant source of the background radiation in the room.

We think that the table above provides a good summary of the contributions of the different physical interactions of X-rays with matter.

With this material you can make either flash cards or make a table and cover up the different squares as you’re going through and just test yourself so that you can identify the different areas that these different interactions impact in terms of dose, and image contrast in X-ray imaging.

summary of x ray

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This Day In History : November 8

Changing the day will navigate the page to that given day in history. You can navigate days by using left and right arrows

summary of x ray

German scientist discovers X-rays

On November 8, 1895, physicist Wilhelm Conrad Röntgen (1845-1923) becomes the first person to observe X-rays, a significant scientific advancement that would ultimately benefit a variety of fields, most of all medicine, by making the invisible visible. 

Röntgen's discovery occurred accidentally in his Wurzburg, Germany, lab, where he was testing whether cathode rays could pass through glass when he noticed a glow coming from a nearby chemically coated screen. He dubbed the rays that caused this glow X-rays because of their unknown nature.

X-rays are electromagnetic energy waves that act similarly to light rays, but at wavelengths approximately 1,000 times shorter than those of light. Röntgen holed up in his lab and conducted a series of experiments to better understand his discovery. He learned that X-rays penetrate human flesh but not higher-density substances such as bone or lead and that they can be photographed.

Röntgen's discovery was labeled a medical miracle and X-rays soon became an important diagnostic tool in medicine, allowing doctors to see inside the human body for the first time without surgery. In 1897, X-rays were first used on a military battlefield, during the Balkan War, to find bullets and broken bones inside patients.

Scientists were quick to realize the benefits of X-rays, but slower to comprehend the harmful effects of radiation. Initially, it was believed X-rays passed through flesh as harmlessly as light. However, within several years, researchers began to report cases of burns and skin damage after exposure to X-rays, and in 1904, Thomas Edison’s assistant, Clarence Dally, who had worked extensively with X-rays, died of skin cancer. Dally’s death caused some scientists to begin taking the risks of radiation more seriously, but they still weren’t fully understood. 

During the 1930s, 40s and 50s, in fact, many American shoe stores featured shoe-fitting fluoroscopes that used X-rays to enable customers to see the bones in their feet; it wasn’t until the 1950s that this practice was determined to be risky business. 

Wilhelm Röntgen received numerous accolades for his work, including the first Nobel Prize in physics in 1901, yet he remained modest and never tried to patent his discovery. Today, X-ray technology is widely used in medicine, material analysis and devices such as airport security scanners.

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HISTORY Vault: 101 Inventions That Changed the World

Take a closer look at the inventions that have transformed our lives far beyond our homes (the steam engine), our planet (the telescope) and our wildest dreams (the internet).

Also on This Day in History November | 8

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Proposition 187 is approved in California

Maurice ferré becomes first puerto rican to lead a major u.s. mainland city, this day in history video: what happened on november 8, beer hall putsch begins, salvatore “sonny” bono is elected to the u.s. congress, the republican revolution.

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X-rays articles from across Nature Portfolio

X-rays are a type of electromagnetic radiation with a wavelength between 0.01 and 10 nanometres. X-rays offer an important method for investigating the atomic structure of crystalline materials and nanometre-scale structures. Distant galaxies and clusters can be detected by the X-rays they emit.

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Brighter organic scintillators by hot exciton manipulation

The fast response and efficiency of plastic scintillators are severely degraded by the preferential population of slow triplet excited states in luminescence centres, such as in dye molecules. This issue can be solved by hot exciton manipulation, which avoids population of the lowest triplet state.

  • Martin Nikl

Latest Research and Reviews

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Ultracompact mirror device for forming 20-nm achromatic soft-X-ray focus toward multimodal and multicolor nanoanalyses

Optics used for X-ray focusing suffer from wavelength dependent effects like chromatic aberration. Here the authors demonstrate fabrication of a ultracompact Kirkpatrick-Baez mirror and use it for achromatic focusing to 20 nm spot for the soft X-ray at 2-keV photon energy.

  • Takenori Shimamura
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Quenched lattice fluctuations in optically driven SrTiO 3

Intense light pulses can induce symmetry breaking, as for the generation of ferroelectricity in SrTiO 3 . Using ultrafast X-ray diffuse scattering at a free-electron laser, nonlinear phonon interactions that occur on such mid-IR excitation are observed, with a theory for the dynamics presented.

  • A. Cavalleri

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Free-electron crystals for enhanced X-ray radiation

Shaping the quantum free electron wavefunction leads to over thousand-fold intensity enhancements and greater directionality in X-ray bremsstrahlung.

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Reconstruction of lateral coherence and 2D emittance in plasma betatron X-ray sources

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Observation of a single protein by ultrafast X-ray diffraction

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Plasma interactions with bespoke laser pulses

Due to dispersion, the group velocity of laser pulses propagating in plasmas slows down with increasing wavelength, which presents challenges for precision-controlled plasma interactions. Now, new techniques for spatio-temporal pulse shaping have lifted this limitation in the demonstration of short-pulse table-top soft X-ray lasers.

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Exploring the Universe with X-Ray Astronomy: Insights from eROSITA

X -ray astronomy has been reshaping our understanding of the cosmos by allowing us to perceive the universe through ‘X-ray vision’—a concept once reserved for the realm of science fiction. Astronomers leverage this technique to investigate some of the most energetic and tumultuous phenomena in space.

The eROSITA consortium at the Max Planck Institute for Extraterrestrial Physics has recently enriched our cosmic perspective with a new X-ray data haul from the eROSITA survey, encapsulating half of the X-ray sky. This compilation showcases about 900,000 distinct X-ray sources, surpassing the total number of such sources previously observed over the entire history of X-ray astronomy.

The versatility of eROSITA—an advanced soft X-ray imaging telescope perched on the Spectrum-RG satellite—is evident from its comprehensive all-sky survey, which reveals a variety of cosmic occurrences and characteristics. Whether it’s detailing the sheer number of supermassive black holes or galaxies’ energetic interactions, eROSITA provides a more nuanced picture of the universe’s structure and evolution.

As the eROSITA team continues sifting through the expansive data sets and sharing them with the global scientific community, we can only anticipate more revolutionary discoveries in the fascinating field of X-ray astronomy.

About eROSITA

eROSITA’s journey in the cosmos, including its pivotal scanning missions, enables a profound analysis of the high-energy universe. With over 50 scientific papers already published based on eROSITA’s findings, the telescope’s contributions enhance our grasp of cosmic events and the environments around supermassive black holes and galaxy clusters.

eROSITA’s Treasury of X-ray Sources

The newly acquired data from eROSITA paints a captivating picture of the cosmos at varying X-ray energy levels, each unravelling different properties of the astronomical sources. This rich dataset lays the groundwork for future endeavors to delve deeper into the universe’s mysteries using high-energy observations.

Zeroing in on Specific X-ray Objects

eROSITA’s focused observations offer invaluable insights into the galactic infrastructure and the dynamics of large-scale cosmic formations. By examining intense X-ray emissions, the telescope sheds light on the interactions occurring within and between galaxy clusters, contributing significantly to our understanding of the cosmos’s formation.

eROSITA’s Past Work and Future

Since its commencement in late 2019, eROSITA has notably advanced X-ray astronomy, providing detailed glimpses into the evolving universe. Its observations of a distant quasar and the hot gas surrounding our galaxy are just a few exemplary highlights of its achievements.

FAQs about X-Ray Astronomy and eROSITA

The groundbreaking work by eROSITA represents a monumental leap in the field of X-ray astronomy, offering a comprehensive X-ray view of the universe. Through advanced technology and dedication, astronomers continue to decipher the enigmatic high-energy realm of the cosmos, deepening our understanding of the universe’s ever-evolving narrative. The vast array of data and images provided by eROSITA promises to keep the astronomical community busy, potentially rewriting the textbooks with new cosmic knowledge.

Exploring the Universe with X-Ray Astronomy: Insights from eROSITA

Bleeding Cool News and Rumors

X-Men '97 Showrunner, Producer on What to Know About Wolverine, Beast

Posted in: Disney+ , Marvel , Preview , streaming , Trailer , TV | Tagged: disney plus , Marvel Studios , preview , trailer , x-men , X-Men '97

X-Men '97 Showrunner Beau DeMayo & Supervising Producer Jake Castorena offer some insights into Wolverine's & Beast's roles in the series.

Article Summary

  • Marvel's X-Men '97 to hit Disney+ on March 20th, bringing classic heroes back.
  • Showrunner and Supervising Producer share insights on Wolverine and Beast's roles in the show.
  • Comic-Con 2023 panel teases footage and updates, including Mr. Sinister's return.
  • Beau DeMayo emphasizes importance of fans working on the X-Men '97 production.

Earlier today, the news that fans had been waiting a long time for was finally announced. On March 20th, Marvel Studios will be bringing X-Men '97 to Disney+ screens – and with that news came an official trailer and poster that wore its X-Men: The Animated Series love on its sleeve. In case you hadn't heard, the voice cast includes Ray Chase as Cyclops, Jennifer Hale as Jean Grey, Alison Sealy-Smith as Storm, Cal Dodd as Wolverine, JP Karliak as Morph, Lenore Zann as Rogue, George Buza as Beast, AJ LoCascio as Gambit, Holly Chou as Jubilee, Isaac Robinson-Smith as Bishop, Matthew Waterson as Magneto, and Adrian Hough as Nightcrawler . Thanks to a profile interview with Empire Magazine , Showrunner Beau DeMayo & Supervising Producer Jake Castorena shared some insights into the beloved characters ahead of next month – for this go-around, we're looking at what they had to share about Wolverine and Beast.

x-men '97

When it comes to Wolverine, DeMayo sees the famed X-Man as the "broken-hearted samurai who thinks he's an animal" who still has a lot to offer from a storyline perspective. Castorena followed that with an interesting observation about the clawed Canadian. "What I love is, he has the most combat [training] of everyone on the team just because he's been alive long enough, and he throws it out the window every time," the supervising producer shared. As DeMayo describes him, viewers can expect the team's resident favorite "uncle" to be the source of both hope and solutions. "He's the guy who's always going to say the right thing, even if he's quoting somebody else. He's always going to have a solution. It may not be the perfect solution, but he's going to try very, very hard to fix the scientific problem of the day," the showrunner added.

x-men '97

DeMayo & Supervising Producer Jake Castorena made a surprise appearance during Marvel's "Designing the X-Men" panel at San Diego Comic-Con 2023 to offer some updates and… wait for it… footage from the series. Yup – but the bad news? It's not going to be released – at least not anytime soon. But what was screened included scenes of the team interrogating Dr. Trask, Jean Grey having some "issues" with Cerebro, Cyclops using his power to save some literally falling teammates, and even a "To me, my X-Men" line thrown in for good measure. Along with the screening, we learned that Jean is pregnant, Archangel & Bishop will be official team members, and Mr. Sinister has a "pretty foolproof plan to destroy the X-Men once and for all." From the production standpoint, we learned that things are going "really, really well" and that not only is post-production work on the first season being finished up but also that they're about to wrap writing the Season 2 finale.

X-Men '97 – Beau DeMayo Clarifies Some Previous Misreporting

Picking up not long after the events of the "final" episode "Graduation Day" (directed by Larry Houston and written by James Krieg ), the series will apparently deal with the fallout stemming from the world witnessing Henry Peter Gyrich shooting Xavier during a Mutant/Human Relations Summit. While Xavier & Lilandra leave for the Shi'Ar home world for Xavier's cure, global support for mutantkind grows. As we've seen in previous previews for the animated series, the X-Men roster will see some changes as Morph and Bishop join the team. Things are apparently so good that Rogue & Gambit consider giving a real-life a shot, while Cyclops & Storm look to continue growing Professor X's dream. Even Magneto was apparently moved enough by Xavier's words & actions to consider giving Xavier's philosophy a try. So, with all of this "happily ever after" stuff going on, what better time for Mr. Sinister to make a return? Now, here's a look at DeMayo's tweet clarifying what was discussed at Marvel Unlimited's X-Men: 60 Uncanny Years Live Virtual Event on March 16th:

@ComicBook_Movie #XMen #xmentas #xmen97 Few sites misreporting an answer from Thursday was an official show synopsis. Not the case. It was only an answer to a question, and I said CYCLOPS and Storm are trying to carry on Xavier's dream. 😘 — Beau DeMayo (@beau_demayo) March 19, 2023

In October 2022, DeMayo fielded some questions on social media that included shedding some light on the upcoming animated series revival. With production first getting underway in Fall 2020 and a second season confirmed, DeMayo sees the animated series as a large part of his life "for the foreseeable future," along with two upcoming non-MCU feature projects. As for the series and how it will be received by a fanbase that's remained faithful to the series since it originally left our screens, DeMayo admitted that it's a concern but also that he's "not worried" because of the "amazing talent" that's working on the series.

DeMayo Only Wanted Fans Working on "X-Men '97" : "My general rule was you had to be a fan. No questions," DeMayo explained. "I've been on [a] show, namely '[The] Witcher,' where some of the writers were not or actively disliked the books and games… even actively mocking the source material. It's a recipe for disaster and bad morale. Fandom as a litmus test checks egos and makes all the long nights worth it." As DeMayo sees it, "you have to respect the work before you're allowed to add to its legacy."

DeMayo Has "Mixed Feelings" on Rogue Controlling Her Powers : "I am aware that Rogue learned to control her powers, and I have mixed feelings on the shift. However, trust me when I say Rogue fans have plenty to be stoked about… in no small part due to [Supervising Producer] Charley Feldman being a massive advocate for her character."

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COMMENTS

  1. X-ray

    X-rays are a form of ionizing radiation—when interacting with matter, they are energetic enough to cause neutral atoms to eject electrons. Through this ionization process the energy of the X-rays is deposited in the matter.

  2. X-ray summary

    X-ray, Electromagnetic radiation of extremely short wavelength (100 nanometres to 0.001 nanometre) produced by the deceleration of charged particles or the transitions of electrons in atoms.

  3. X-Rays: Uses, Procedure, Results

    Summary . X-rays are imaging tests that use small amounts of electromagnetic radiation to view the inside structures of your body. In addition to conventional X-rays, several other specialized forms of X-rays capture images in more precise ways. Sometimes a contrast agent can help healthcare providers see things better.

  4. X-ray: Imaging test quickly helps find diagnosis

    A feeling of warmth or flushing. A metallic taste. Lightheadedness. Nausea. Itching. Hives. Rarely, severe reactions to a contrast medium occur, including: Very low blood pressure. Difficulty breathing. Swelling of the throat or other parts of the body. How you prepare Enlarge image X-ray exam Enlarge image

  5. X-ray

    X-ray (or much less commonly, X-radiation) is a high-energy electromagnetic radiation. In many languages, it is referred to as Röntgen radiation, after the German scientist Wilhelm Conrad Röntgen, who discovered it in 1895 [1] and named it X-radiation to signify an unknown type of radiation. [2]

  6. X-ray

    X-ray or radiography uses a very small dose of ionizing radiation to produce pictures of the body's internal structures. X-rays are the oldest and most frequently used form of medical imaging. They are often used to help diagnosed fractured bones, look for injury or infection and to locate foreign objects in soft tissue.

  7. Plain Film X-Ray

    X-rays are a type of electromagnetic radiation (just like visible light). There are three criteria that must be met to allow electromagnetic radiation to be used for imaging purposes: Ability to create to the electromagnetic radiation at the wavelength required Ability to focus the radiation on a particular area

  8. X-rays

    resources Summary X-rays are a form of ionizing electromagnetic radiation… with wavelengths in the approximate range of 10 −9 m to 10 −12 m (1 nm to 1 pm) with photon energies in the approximate range of 10 3 eV to 10 6 eV (1 keV to 1 MeV) X-rays are formed by… decelerating charges

  9. X-rays

    X-rays are a form of electromagnetic radiation, similar to visible light. Unlike light, however, x-rays have higher energy and can pass through most objects, including the body. Medical x-rays are used to generate images of tissues and structures inside the body.

  10. 30.4: X Rays

    X-Ray Diffraction and Crystallography. Since x-ray photons are very energetic, they have relatively short wavelengths. For example, the 54.4-keV \(K_{\alpha}\) x ray of Example has a wavelength \(\lambda = hc/E = 0.0228 \, nm\). Thus, typical x-ray photons act like rays when they encounter macroscopic objects, like teeth, and produce sharp shadows; however, since atoms are on the order of 0.1 ...

  11. How X-rays Work

    As with many of mankind's monumental discoveries, X-ray technology was invented completely by accident. In 1895, a German physicist named Wilhelm Roentgen made the discovery while experimenting with electron beams in a gas discharge tube.Roentgen noticed that a fluorescent screen in his lab started to glow when the electron beam was turned on. This response in itself wasn't so surprising ...

  12. What are X rays? A simple introduction

    X rays are a kind of super-powerful version of ordinary light: a higher- energy form of electromagnetic radiation that travel at the speed of light in straight lines (just like light waves do).

  13. X-ray: How It Works, What to Expect, and More

    An X-ray is a common method of scanning the body. Doctors and dentists use X-rays to get clear images of bones, tissue, organs, or teeth. X-rays use a form of ionizing radiation to take images. This is similar to light, except X-rays have higher energy, meaning they can pass through the body.

  14. X-Rays: MedlinePlus

    Summary X-rays are a type of radiation called electromagnetic waves. X-ray imaging creates pictures of the inside of your body. The images show the parts of your body in different shades of black and white. This is because different tissues absorb different amounts of radiation. Calcium in bones absorbs x-rays the most, so bones look white.

  15. X-Rays

    White Marsh See additional imaging locations How are X-rays performed? X-rays can be performed on an outpatient basis, or as part of inpatient care. Although each facility may have specific protocols in place, generally, an X-ray procedure follows this process:

  16. Production and Properties of X-Rays

    Summary. The inside parts of the x-ray tube are the anode and the cathode. The cathode consists of the focusing cup and filament. When x-rays are produced, electrons are released from the filament, given a high speed, and focused into a small group by the focusing cup. When they zoom over to the anode, they are stopped suddenly.

  17. A brief history of x-rays

    X-ray analysis techniques were adopted in other life science sub-fields, such as virology, in which crystalline forms of plant viruses were being prepared in the 1930s, rendering x-ray analysis feasible. By 1956, Crick and Watson concluded from such analysis that a small virus contains identical subunits, packed together in a regular manner. ...

  18. X-ray Production

    X-rays are a form of electromagnetic radiation with wavelengths ranging from 0.01 to 10 nanometers. In the setting of diagnostic radiology, X-rays have long enjoyed use in the imaging of body tissues and aid in the diagnosis of disease.

  19. X-Ray Interactions, Illustrated Summary (Photoelectric, Compton

    Summary Overview of the Physics Behind X-Ray Interactions When x-rays interact with the human body during an x-ray exposure, they form an image that is highly dependent on the type of interactions of matter and x-rays. Diagnostic x-ray interactions are dominated by two different physical interactions - the photoelectric effect and Compton scatter.

  20. German scientist discovers X-rays

    This Day In History: 11/08/1895 - Scientist Discovers X-rays. On November 8, 1895, physicist Wilhelm Conrad Röntgen (1845-1923) becomes the first person to observe X-rays, a significant ...

  21. X-rays

    X-rays are a type of electromagnetic radiation with a wavelength between 0.01 and 10 nanometres. X-rays offer an important method for investigating the atomic structure of crystalline materials ...

  22. X-ray survey bolsters prevailing theory of universe's expansion

    The first x-ray survey of the universe in decades has cataloged and measured the biggest lumps in the cosmos: clusters of hundreds or thousands of galaxies. Their masses show how fast matter clumped together over cosmic history, and they tell a story that is at once satisfying and frustrating: The universe is about as lumpy as the standard ...

  23. Wilhelm Conrad Roentgen

    Wilhelm Conrad Röntgen (born March 27, 1845, Lennep, Prussia [now Remscheid, Germany]—died February 10, 1923, Munich, Germany) physicist who received the first Nobel Prize for Physics, in 1901, for his discovery of X-rays, which heralded the age of modern physics and revolutionized diagnostic medicine. Röntgen studied at the Polytechnic in ...

  24. Exploring the Universe with X-Ray Astronomy: Insights from eROSITA

    X-ray astronomy has been reshaping our understanding of the cosmos by allowing us to perceive the universe through 'X-ray vision'—a concept once reserved for the realm of science fiction.

  25. X-Men '97 Showrunner, Producer on What to Know About Wolverine, Beast

    Article Summary. Marvel's X-Men '97 to hit Disney+ on March 20th, bringing classic heroes back. Showrunner and Supervising Producer share insights on Wolverine and Beast's roles in the show.