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15 March 2010

Answer to Question #7820 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 am an interventional radiological technologist who works in a catheterization laboratory. I work with a cardiologist who believes that by lowering the patient closer to the tube during cases, we are reducing scatter from the x-ray tube. I believe the only thing we are really doing is increasing dose to the patient by reducing distance from the source and that there is no significant amount of scatter from the x-ray tube. I tried looking for anything about radiation safety and table height but was unable to locate any information. Is he correct?

From Wagner and Archer, "keep the patient at a maximum distance from the x-ray tube" because x-ray intensity at the patient's skin surface is decreased as the distance increases. In addition, "keep the image intensifier as close to the patient as possible" because this will minimize the x-ray concentration at the skin surface.

Scatter radiation comes from the patient, is directly proportional to the amount of x ray striking the patient, and is a maximum at a 90-degree angle to the primary x-ray beam. If you move the patient farther away from the x-ray tube, the scatter radiation will decrease because the amount of x ray striking the patient has decreased.

So, in this case, you are correct!

Ken "Duke" Lovins, CHP

Reference
Wagner LK, Archer BR. Minimizing risks from fluoroscopic x-rays. Third Ed. Available at: www.rmpartnership.com.

Answer posted on 14 October 2008. The information and material posted on this Web site is intended as general reference information only. Specific facts and circumstances may alter the concepts and applications of 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 specific to whatever facts and circumstances are presented in any given situation. Answers are correct at the time they are posted on the Web site. Be advised that over time, some requirements could change, new data could be made available, or Internet links could change. For answers that have been posted for several months or longer, please check the current status of the posted information prior to using the responses for specific applications.