Answer to Question #10818 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Equipment

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

Q

I did an experiment on scatter radiation using CR (computed radiography). I exposed a spine phantom and put a hand phantom with a cassette approximately 2 m from the table bucky. There is a formation of the image of the hand phantom by using only the scattered radiation from the spine phantom.

If there is an image produced, then there is an interaction with the scattered radiation. If the dose is considered negligible, then why is there still an interaction with the scattered radiation? Do you think that the interaction can be considered as dangerous?

A

Computed radiography (CR) x-ray cassettes are designed to be highly sensitive to radiation, specifically to keep patient doses as low as possible. Consequently, it should not be surprising that cassettes exposed to scatter radiation will show a shadow from an object placed between it and a scattered radiation source. CR cassettes will show noticeable darkening even from background radiation if they are stored for a few days and not erased before use. Consequently, it is always good practice to protect unexposed cassettes by placing them in an area where they are not subject to stray radiation before they are used for imaging purposes. Also, any cassettes which have not been recently used, should be erased before they are reemployed for imaging purposes. You may want to review the article recently published in the January 2011 issue of the American Journal of Radiography, "Computed Radiography Image Artifacts Revisited." (AJR:196; January 2011)

Mike Bohan
RSO/Medical Physics

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