Answer to Question #9049 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Shielding

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

I work in an architectural firm that designs medical facilities. Some of the designs I have seen of x-ray rooms incorporate a small shielding wall and window inside the room where the technician goes while the x ray is being performed. My concern is that this small area is not sealed with a door, but has only a cased opening. While the opening is not directly in a "line of sight" with the x ray, my concern is about the ability of x rays to "bounce" off of walls and expose the technician unnecessarily. Is there any validity to my concerns?

You raise an excellent question and for the right reason! The answer lies in Structural Shielding Design for Medical X-Ray Imaging Facilities. For radiographic installations (i.e., diagnostic):

"The operator of a radiographic unit shall remain in a protected area (control booth) or behind a fixed shield that will intercept the incident radiation. The booth shall be positioned so that no unattenuated primary or unattenuated single-scattered radiation will reach the operator's position in the booth. There shall not be an unprotected direct line of sight from the patient or x-ray tube to the x-ray machine operator or to loaded film cassettes placed behind a control booth wall."

There is additional information provided regarding the viewing window and other aspects, but the above is the basis for the answer to your question.

There will be some minimal amount of radiation dose to an operator behind a control wall from multiple scattered x rays. As long as there is no unattenuated primary or unattenuated single-scatter radiation, then those doses will remain minimal.

Ken "Duke" Lovins, CHP

National Council on Radiation Protection and Measurements. Structural shielding design for medical x-ray imaging facilities. Bethesda, MD: National Council on Radiation Protection and Measurements; NCRP Report No. 147:11; 2004. Available at: Accessed 30 April 2010.

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