What Is An X-ray?

Woman getting x-ray of neck.
Woman getting x-ray of neck.. Science Photo Library Ltd/Getty Images

How Does X-Ray Work?

Every day you use objects that utilize different wavelengths from the electromagnetic spectrum. All wavelengths within the spectrum give off energy in the form of electromagnetic radiation (EMR). We use this energy every day including (listed from longest waves to shortest waves):

  • Radio waves - AM/FM radio
  • Microwave - reheat a meal from last night or make popcorn
  • Infrared - most remote controls, thermal heat-detecting goggles
  • Visible - allows us to see different colors
  • Ultraviolet - behind sunburns in the summertime
  • X-ray - useful in the medical field for seeing inside the body
  • Gamma-ray - also useful in medical imaging

X-ray is one of the forms of electromagnetic radiation that can be used to take an image of the internal structures of the body. An x-ray machine sends out tiny particles, which pass through all but the most solid of objects such as bones and metal, creating a special image known as a radiograph. Bones and any metal objects will appear white on the radiograph. Muscle, fluid and fat will show up as a gray on the image, while air will appear black. The black and white image that is created forms an image that can be very useful to doctors in helping determine your medical diagnosis.

Risks Associated With X-Ray

Having an x-ray is not painful, but if performed very frequently, can carry a risk of developing cancer later on in life.

This risk is very low and must be weighed against the benefit of having the images. It is especially important that you notify the x-ray technician if you are pregnant.

The actual associated risk from radiation exposure is mostly estimated from atomic bomb survivors in Japan from 1945. To better understand this, two terms are particularly important.

Roentgens is a term that is used to describe the amount of radiation in a volume of air. The term is named after the founder of x-ray, Wilhelm Roentgen, in 1895. Effective dose is measured in sieverts (Sv) which numerically describe a whole body dose of radiation. The higher the number, the more radiation exposure you are receiving.

There are varying estimates as to how significant the risk for acquiring cancer is from radiation exposure, however CT scans seem to pose the greatest risk. A single x-ray has a low radiation exposure and is generally around 0.02 milisieverts (mSv). A CT scan can range from 2 mSv (Head CT) to 16 mSv (Coronary CT Angiogram), which is the equivalent of 100 to 800 x-rays.

What To Expect For An X-Ray

You may be asked to wear a hospital gown and to take off any jewelry you're wearing because it will show up on the x-ray. Depending on the area you are having imaged you may be asked to pose in different positions, some of which may be slightly awkward. However, it only takes a second to take the x-ray, so this is very temporary.

Also, depending on the area you are having imaged, the technician may take several shots from different angles. The images are usually interpreted by a doctor called a radiologist, who specializes in analyzing these tests. The results are then sent to your physician.

Is The Risk Worth It?

It is important to have this discussion with your physician. You should always ask, "will the x-ray or ct scan make an impact in my care?" If the imaging study is not likely to change things, you will probably be better off to skip the test. However if treatment will likely change dependent upon the results of the x-ray or ct scan, then it will most likely be worth the small risk.


Chandra X-Ray Center. (n.d.). Where does the "X" in "X-ray" come from? Accessed on June 25, 2016 from http://chandra.harvard.edu/blog/node/62

High Energy Astrophysics Science Archive Research Center. (2014). The Electromagnetic Spectrum. Accessed on June 24, 2016 from http://imagine.gsfc.nasa.gov/science/toolbox/emspectrum1.html

Lee, C.I. & Elmore, J.G. (2015). Radiation-related risks of imaging studies. Accessed on June 25, 2016 from http://www.uptodate.com (Subscription Required).

Medline Plus Medical Encyclopedia. X-ray. Accessed: February 24, 2010 from http://www.nlm.nih.gov/medlineplus/ency/article/003337.htm

U.S. Food and Drug Administration. (2016). What Are The Radiation Risks From CT? Accessed on June 25, 2016 from http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115329.htm

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