X ray Basics

Also called: Roentgenogram, Roentgenography, Radiograph, Roentgen Rays

Reviewed By:
David Slotnick, M.D.

Summary

An x-ray is a painless test in which an image is created of part of the body by using low doses of electromagnetic radiation that are reflected on film paper or fluorescent screens. X-rays or radiography can be used to diagnose many conditions, including:

• Bone breaks, chips and fractures
  
  
• Sprains and strains
  
  
• Tooth or jaw abnormalities
  
  
• Progression of degenerative diseases such as arthritis

An x-ray is painless and does not typically cause any side effects when administered correctly. A lead apron is usually worn to protect organs from radiation damage. Although the rays of radiation pose very little risk, x-rays may be harmful to developing fetuses. Therefore, women who are or may be pregnant should inform their physician or x-ray technologist of the condition.

Some modern tests (e.g., CAT scan) use computers along with x-rays to create three-dimensional imaging. X-ray tests are typically  viewed by an x-ray specialist (radiologist) before the results are explained to the patient.

Special requirements may be necessary before administering some specialized x-rays. Certain x-ray tests require a contrast medium to be injected, swallowed, or inserted. This helps outline certain internal structures on the x-ray image. X-ray tests requiring a contrast medium can take as long as an hour. However, many standard x-rays take only a few seconds or minutes (e.g., dental x-ray).

About x-rays

An x-ray is a painless test in which part of the body is imaged by using low doses of electromagnetic radiation that are reflected on film or fluorescent screens. These images are more commonly known as x-rays, and also as radiographs or roentgenograms. The images may be used to diagnose and monitor the treatment of various diseases.

X-rays are noninvasive, relatively inexpensive and fast. It is generally safe for people of all ages when used correctly. Medical professionals perform x-rays to diagnose many conditions, including:

• Determining if bones are broken, fractured, or chipped
  
  
• Assessing sprains and strains
  
  
• Monitoring progression of degenerative diseases such as arthritis
  
  
• Monitoring dental health or diagnosing the source of dental problems

X-ray results are two dimensional, with the boundaries between internal structures often blurred on x-ray film. Consequently, results may be misleading or inconclusive in some instances. In some cases, a series of x-ray tests over a period of time may also be needed to assess a condition or compare changes.

The X-ray works by passing small amounts of electromagnetic radiation through the body to produce images of bones, teeth and internal organs. The type of x-ray test administered depends on which part of the body needs to be examined.

X-rays are the oldest imaging technology still in use today.X-rays were discovered almost by accident in the 1890s by a German scientist named Wilhelm Conrad Roentgen. Because no one understood the rays that were at work in forming these images, the rays were initially called x-rays. Much more is now known about this form of radiation.

Bones and cartilage (the tissue that connects bones and joints) tend to be dense and absorb x-rays better than do soft tissues (e.g., skin, fat, internal organs). As a result, bones appear white on x-rays, whereas soft tissues usually appear as shades of gray. Organs or structures containing mostly air, such as the lungs, appear black. Generally, the denser the bone or organ, the more clearly it will appear during the x-ray. The use of a contrast medium makes certain areas of the body easier, or possible, to visualize using radiographic techniques.

The results may first be viewed by a physician with special training in interpreting radiography results (radiologist) before the primary care physician explains the results to the patient.

An x-ray machine produces a beam of radiation that is pointed by a tube at the part of the body being examined. The area to be examined is placed between the film and the x-ray tube, which is surrounded in lead casing except for a small opening through which the rays are beamed. Within the x-ray tube, a beam of electrons is fired into a target composed of a chemical element known as tungsten, emitting photons that travel straight and outward from the point on the target to the area being x-rayed. The resulting images are recorded on either film or a fluorescent screen.

The energy contained in the photons may cause some cell damage. Most of this cell damage is repaired quickly, but in some cases may be permanent. However, the low doses of radiation in modern x-ray tests are considered very safe. Most physicians feel the benefits of radiography outweigh the very small risk associated with the procedure. However, young children and developing fetuses are more sensitive to radiation. Women should advise their physician if they are pregnant before getting an x-ray.

Additional techniques may be necessary to get a clear view of softer tissues, hollow areas or fluid-filled body parts. For example, a physician may administer one of a variety of special materials known as contrast mediums to produce sharper contrasts in light and dark areas on the x-ray. These contrasts give the physician a clearer image of areas such as the urinary tract, the spinal cord, blood vessels and the gallbladder.

Types and differences of x-rays

In addition to standard x-ray tests, there are a number of specialized radiography tests that can provide more specific information about an illness, injury or abnormality. These specialized radiography tests include:

• CAT scan (computed axial tomography). This noninvasive or minimally invasive test uses multiple x-ray images, taken from different angles, to create three-dimensional images of body structures. It may be performed alone or with the use of a contrast medium. A CAT scan is used when an area inside the body needs to be viewed from multiple angles and in greater detail.
  
  
• Fluoroscopy. This type of test uses radiography to image internal body organs while they are in motion. A continuous x-ray beam is focused on the part of the patient being examined to create a detailed, moving image that appears on a monitor – much like a movie.
  
  
• Angiography. An angiography is a radiography procedure in which contrast material is injected through a catheter to the arteries of the heart. This allows the physician to detect if there is obstruction in coronary arteries. Angiography may be performed if the patient is experiencing abnormal chest pain.
  
  
• Barium x-ray. With this type of imaging test, a patient is given a chalky solution containing barium. The barium coats the insides of the digestive system, allowing this area to be viewed in greater detail with an x-ray. Barium x-rays may involve the upper gastrointestinal tract, where a barium solution is swallowed to outline the esophagus, stomach and a portion of the small intestine. For the lower portion of the gastrointestinal tract, a barium enema is used to outline the rectum and colon. These tests may be used to determine causes of intestinal or abdominal pain (e.g., peptic ulcers, irritable bowel syndrome).

X-rays in the body

X-ray is a procedure used on many types of the body to diagnose or monitor various illness or conditions. X-ray, or radiographic, studies specific to certain body systems include:

• Arthrography. Radiographic examination of a joint. Contrast medium and/or air are inserted into the joint and used to outline the soft tissue and joint structures. It is most commonly performed to reveal problems associated with the shoulder, wrist, hip, knee and ankle.
  
  
• Bone x-ray. Radiography is the fastest and easiest way to view broken bones, joint or spine injuries. Images can reveal fine hairline fractures or bone chips. At least two images from different angles are taken. In many cases, several images are needed, especially if the problem involves a joint. Radiography also may be used ensure that a fracture has been properly aligned and stabilized at the beginning of the healing process.
  
  
• Chest x-ray. The most commonly performed form of diagnostic radiography, it takes images of the heart, lungs, airways, blood vessels and the bones of the spine and chest. It is used to diagnose many conditions, including chest pain, emphysema, heart problems, lung cancer and pneumonia. A chest x-ray may also be performed to locate objects, such as coins, a child may have swallowed.
  
  
• Dental x-ray. These x-rays can monitor tooth growth and identify dental problems, such as cavities, abscesses and impacted wisdom teeth. They may also be used to monitor changes in the jaw or gum disease.
  
  
• Discography. This test is a type of fluoroscopy that may be performed on patients who are considering back surgery or who have not responded well to conventional treatments for lower back pain.
  
  
• Hysterosalpingography. Also known as uterosalpingography, it is an x-ray examination of the uterus and fallopian tubes. In this procedure, the type of radiography known as fluoroscopy is used with a contrast material, which is injected into the uterus via the cervix. It may be performed on women who are having difficulty becoming pregnant or who have experienced repeated miscarriages. It also is used to reveal the presence of uterine fibroids and tumors and to monitor the effects of fallopian tube surgery.
  
  
• Intravenous pyelogram (IVP). Radiographic examination of the kidneys, ureters and urinary bladder. Contrast material is used. This form of radiography helps reveal abnormalities in the urinary system. It also can tell a physician how efficiently the patient's urinary system is able to handle waste. Enlarged prostate, kidney stones and tumors all may be diagnosed through this technique.
  
  
• Lower gastrointestinal (GI) tract radiography. Radiographic examination of the large intestine (colon). It uses fluoroscopy and contrast material and can diagnose or monitor conditions such as constipation, ulcers, benign tumors, cancer and signs of other intestinal illnesses. This procedure can also be useful in diagnosing inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis.
  
  
• Mammography. Radiographic procedure that examines the breasts to help diagnose breast diseases in women. It is also used as a screening tool to help identify breast cancer, or potentially cancerous tissues. A specially designed x-ray machine flattens the breast and exposes only breast tissues to the x-rays. A radiographic procedure called galactography uses mammography to create images (galactograms) of the inside of the breast's milk ducts.
  
  
• Myelography. Radiographic examination of the spinal cord and the space surrounding it (subarachnoid space). Contrast material is used in this procedure. It can aid the diagnosis of herniated or ruptured intervertebral disks, bone spurs, spinal stenosis (narrowed spinal column), tumors, infection, inflammation of the arachnoid membrane (which covers the spinal cord), abnormalities of blood vessels supplying the spinal cord and damage caused by injuries.
  
  
• Upper gastrointestinal tract radiography. Radiographic examination of the pharynx, esophagus, stomach and first part of the small intestine (duodenum). It uses fluoroscopy and a contrast material. Conditions that are revealed through this procedure include blockages, hiatal hernias, inflammation, problems with the muscular wall of gastrointestinal tissues, scarring, tumors and ulcers.
  
  
• Voiding cystourethrogram (VCUG). Radiographic examination of the bladder and lower urinary tract. It involves the insertion of a contrast medium through a catheter placed in the ureter. The patient then empties the bladder while images are taken. This test is often recommended for children with urinary tract infections to check for a condition known as vesicoureteral (VU) reflux. This is a condition in which the valve of the ureters allows urine to flow backward into the ureters.

Before the x-ray procedure

X-rays may occur in a laboratory, physician’s office or hospital. In general, no special preparation is needed before an x-ray is taken, unless a special material called a contrast medium is going to be used. Contrast mediums outline a specific body area internally. They can be swallowed, injected into a vein or inserted rectally, and produce a dull, opaque appearance on film.

If a contrast medium will be used, patients may be asked not to smoke, eat or drink after midnight before the test, and the physician may make minor changes in how the patient takes his or her medications or supplements. The physician will also ask about the patient’s history of allergies to screen for a potential allergic reaction to dyes or other materials that may be used in contrast mediums.

A scheduled mammogram requires preparation. The patient will be asked to avoid using deodorant, antiperspirant or lotions on the breast or under the arms before the test. These products can interfere with the quality of the image produced. Women who experience premenstrual breast tenderness may prefer to schedule their mammograms after their periods.

A radiology technician or specially trained nurse generally takes x-ray films. At the time of the test, the technician will ask the patient to remove any objects that may interfere with the image (e.g., clothing, jewelry, wigs, watches and/or dentures). Splints or prosthetic limbs may also be removed in some cases.

Patients should inform the examiner if they have had an x-ray using a contrast dye or barium in the past few days. They should also make sure the examiner is aware of all medications that have been taken recently, including over-the-counter medications or supplements.

Female patients should be sure to inform the examiner if they are or may be pregnant because x-rays can be harmful to fetuses in very rare cases. In cases where the benefits of radiography outweigh the potential risks, pregnant women may wear a lead apron over their abdomen during the test.

A lead apron usually is worn by patients to help protect sex organs from x-rays. In high doses, eggs and sperm can be affected by radiation. However, the risk of this occurring as a result of a radiography test is extremely low. Women should also inform the examiner if they currently have an IUD (a form of birth control) implanted.

During and after the x-ray procedure

X-rays are performed by most physicians and dentists for a variety of conditions and diseases. Depending on the procedure, the patient will sit, stand or lie down between the x-ray machine and x-ray film. Pillows or soft weights may be used to hold the patient in position if necessary. Momentary compression of the body area being examined is occasionally needed for some x-ray tests.

The x-ray machine is then pointed at the area being examined. While exposed to x-rays, the patient may be encouraged to hold their breath to help remain still. Movement during an x-ray test can cause images to blur on film. Multiple x-rays may be taken from different angles if necessary. In the case of dental x-rays, a small piece of film is usually placed in the mouth behind the teeth being tested. The patient bites down on attached paper to hold the film in place before the x-ray is taken.

Radiography tests can be as short as a few seconds (e.g., dental x-rays) or minutes (e.g., bone x-ray), or take as long as an hour in cases where a contrast medium has been administered (e.g., barium enema). Occasional swelling, pain or redness may be experienced at the injection site if a contrast medium is administered this way. The x-ray film is usually developed within a few minutes. A physician who specializes in interpreting x-rays (radiologist) may first view the results. Additional x-rays may be taken from different angles if necessary.

Patients can resume normal activities immediately following the radiography test. The radiologist or the patient’s physician will interpret the findings and review them with the patient either that same day or during a follow-up visit. Additional tests (e.g., CAT scan, MRI) may be necessary if the x-rays do not provide enough information on the tissues or structures being studied.

Potential risks with x-rays

The levels of radiation used in x-ray procedures are so low that they pose only minimal risk to patients. As a precaution, some patients may be asked to wear a lead apron to shield reproductive organs from exposure to radiation. At very high doses, radiation can damage a woman’s eggs or a man’s sperm.

High doses of radiation can also be harmful to a developing fetus. Therefore, women who are or may be pregnant should be sure to inform the physician and x-ray technologist of the condition. It may be necessary to take certain precautions to protect the fetus.

Some precautions a patient may request for an x-ray include:

• Ask the physician how an x-ray will help. Patients have a right to understand why a physician believes an x-ray is necessary. If it is medically necessary, it should not be refused because the small risk of radiation is much lower than the risk of not having a condition properly diagnosed. Patients should not insist on having an x-ray if it is not medically necessary.
  
  
• Ask for gonad shields for x-rays of the lower back, abdomen or area near the sex organs. These lead shields can protect a man’s testicles or a woman’s ovaries from radiation, which protects reproductive cells. This shield should be considered for any patient who may have children in the future. However, in some cases – such as x-rays of the gonads – these shields are not an option.
  
  
• Keep track of x-rays with an x-ray record card. Patients who have x-rays taken should record the date, type of exam and where the x-ray is kept. In some cases, these old x-rays can be used instead of taking new x-rays. Each family member should have an x-ray card.
  
  
• Some radiography procedures require the patient to swallow a contrast medium. In rare cases, patients experience an allergic reaction to the dyes that may be used. Patients with a history of such reactions should inform their physician and x-ray technologist.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about x-rays:

1. What type of x-ray is recommended?
   
   
2. How long will this particular test take?
   
   
3. Will this rx-ray require the use of a contrast medium?
   
   
4. Does it require any preparation on my part?
   
   
5. I think I’m pregnant. Should I wait to have a x-ray?
   
   
6. How much radiation will be used for this particular x-ray test?
   
   
7. What is the margin of error for x-rays in detecting diseases, broken bones, etc.?
   
   
8. Will I receive other tests in addition to the x-ray?
   
   
9. I recently had an x-ray. Am I at risk for being exposed to too much radiation if I have another?
   
   
10. When is it safe for my child to have an x-ray?