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19 July 2008

Answer to Question #341 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Diagnostic X Ray and CT

The following question was answered by an expert in the appropriate field:

What is ESE (entrance skin exposure) and what do you know about what is being done about it and what are some good resources for finding out more?

Since radiation measurement devices can’t be put just under the skin of patients undergoing x-ray exams, we use a radiation instrument with a "phantom" (a plastic sphere or square to represent a body) in the beam to estimate entrance skin exposure dose for various exams. The radiation instrument is placed on the phantom to catch the x rays just as they enter the phantom. The instrument result is actually an exposure-in-air measurement and we use it to estimate skin dose and to calculate organ doses (for organs that lie in the x-ray path). The ESE is measured in units of Roentgen (R) or milliRoentgen (mR). The Food and Drug Administration occasionally distributes information regarding acceptable ESEs. Institutions are not required to comply with them but those wanting to have the best standard of practice will determine methods to comply with acceptable ESEs, often making them even lower. The Food and Drug Administration Web site might be able to provide some useful information or provide you with a contact if you’re interested in further information on this topic. Kelly Classic Certified Medical Health Physicist

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