Health Encyclopedia

X-ray

Definition

X-rays are a form of electromagnetic radiation, just like visible light. In a health care setting, a machines sends are individual x-ray particles, called photons. These particles pass through the body. A computer or special film is used to record the images that are created.

Structures that are dense (such as bone) will block most of the x-ray particles, and will appear white. Metal and contrast media (special dye used to highlight areas of the body) will also appear white. Structures containing air will be black and muscle, fat, and fluid will appear as shades of gray.

Alternative Names

Radiography

How the test is performed

The test is performed in a hospital radiology department or in the health care provider's office by an x-ray technologist. The positioning of the patient, x-ray machine, and film depends on the type of study and area of interest. Multiple individual views may be requested.

Much like conventional photography, motion causes blurry images on radiographs, and thus, patients may be asked to hold their breath or not move during the brief exposure (about 1 second).

How to prepare for the test

Inform the health care provider prior to the exam if you are pregnant, may be pregnant, or have an IUD inserted.

If abdominal studies are planned and you have had a barium contrast study (such as a barium enema, upper GI series, or barium swallow) or taken medications containing bismuth (such as Pepto-Bismol) in the last 4 days, the test may be delayed until the contrast has fully passed.

You will remove all jewelry and wear a hospital gown during the x-ray examination because metal and certain clothing can obscure the images and require repeat studies.

How the test will feel

There is no discomfort from x-ray exposure. Patients may be asked to stay still in awkward positions for a short period of time.

What the risks are

During a single radiograph, a small fraction of the x-rays pass right through the body. The remaining photons are absorbed by tissues in the body. The energy of the absorbed photons can break apart (ionize) compounds, and this may cause cell damage. Most cell damage is soon repaired. However, some is permanent.

For the exposures encountered in conventional radiography, the risk of cancer or heritable defects (due to damaged ovarian cells or sperm cells) is very low. Most experts feel that this low risk is largely outweighed by the benefits of information gained from appropriate imaging. X-rays are monitored and regulated to provide the minimum amount of radiation exposure needed to produce the image.

Young children and developing fetuses carried by pregnant women are more sensitive to the risks of x-rays. Women should tell health care providers about suspected pregnancy.

For additional information regarding why the test is performed and normal and abnormal results, please see the specific x-ray topics:

Review Date:10/23/2006
Reviewed By:Stuart Bentley-Hibbert, MD, PhD, Department of Radiology, Weill Cornell Medical Center, New York, NY. Review provided by VeriMed Healthcare Network.

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