Answer to Question #11739 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 next to a new computed tomography (CT) room which has lead-lined walls, but the ceiling is not lead lined. It is a standard drop ceiling with the second floor a little more than a meter above that. I was wondering about radiation coming from the ceiling over the walls into the next room where I work. I can move a ceiling tile and see into the CT room. Am I being exposed to CT radiation?


I can understand your concern regarding your potential radiation exposure. However, radiation (lead) shielding is designed by qualified medical physicists who have extensive experience with the situation you are describing. They take into account the distance from the CT scanner (from the scanner to the ceiling and back down into your room), the fact that the radiation is not direct but scattered from the ceiling above the scanner, the amount of time someone would spend in the room where you are working, and the amount of time the CT scanner is in use. After all of these factors are considered, the amount of radiation you would receive would be negligible, i.e., less than the naturally occurring background radiation you receive.

If you are still concerned, I suggest you contact your institution's radiation safety officer (RSO) and ask them to provide a dosimetry badge that you could place near where you work for a month or so. This will show you that the radiation exposure level is negligible.

Joel E. Gray, PhD, FAAPM

Answer posted on 18 October 2016. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.