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20 July 2008

Answer to Question #5745 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Equipment

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

I recently had to have a contrast-medium series of x rays to confirm the presence of a small stone in the kidney/ureter/bladder area. Each of these four images taken (including the plain x ray at the beginning) seemed to last for around three to five seconds with the machine making its noise whilst I held my breath. When I returned for a plain x ray a few weeks later to check on the stone, the noise and breath hold lasted for a second or less. I have been trying to find information on exposure times but usually find nothing or some information that says they last for a second or less. Are you able to explain the differences above?

Discussion with a certified x-ray technologist confirmed that the typical x-ray exposure time for this procedure is on the order of less than one second. Typically, you are asked to hold your breath when the technologist pushes the "prep" or "rotor" button. It typically takes one to three seconds before the x ray is actually produced. Most x-ray units "beep" only during the x-ray exposure. Some x-ray tubes start to become noisy as they age, and this is most likely what you heard prior to the actual x-ray exposure, making it sound like the exposure was longer than it actually was.

Ken "Duke" Lovins, CHP

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