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.
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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 the image is being taken.
Geleijns J, Tack D. Medical physics: radiation risks. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology: A Textbook of Medical Imaging. 6th ed. Philadelphia, PA: Elsevier Churchill Livingstone; 2015:chap 1.
Mettler FA Jr. Introduction: an approach to image interpretation. In: Mettler FA Jr, ed. Essentials of Radiology. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 1.
Linda J. Vorvick, MD, Clinical Associate Professor, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.