X-rays are a type of electromagnetic radiation, just like visible light.
An x-ray machine sends individual x-ray particles through the body. The images are recorded on a computer or film.
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.
How the test is performed
The test is done in a hospital radiology department or in the health care provider's office. How you are positioned depends on the type of x-ray being done. Several different x-ray views may be needed.
You need to stay still when you are having an x-ray. Motion can cause blurry images. You may be asked to hold your breath or not move for a second or two when they image is being taken.
How to prepare for the test
Before the x-ray, tell your health care team if you are pregnant, may be pregnant, or if you have an IUD inserted.
Metal can cause unclear images. You will need to remove all jewelry and may need to wear a hospital gown.
How the test is done depends on the specific type of x-ray.
How the test will feel
X-rays are painless. However, some body positions needed during an x-ray may cause temporary discomfort.
What the risks are
X-rays are monitored and regulated so you get the minimum amount of radiation exposure needed to produce the image.
For most conventional x-rays, the risk of cancer or defects is very low. Most experts feel that benefits of appropriate x-imaging greatly outweight any risks.
Young children and babies in the womb are more sensitive to the risks of x-rays. Tell your health care provider if you think you might be pregnant.
For more information, see the specific x-ray topics:
Mettler FA. Introduction: an approach to image interpretation. In: Mettler FA, ed. Essentials of Radiology. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2005:chap 1.
Goldstone K, Yates SJ. Radiation issues governing radiation protection and patient doses in diagnostic imaging. In: Adam A, Dixon AK, eds. Grainger& Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 5th ed.New York, NY: Churchill Livingstone; 2008:chap 9.
Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.