Answer to Question #11148 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Shielding

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


Is it possible for any amount of scatter x-radiation to travel as far as behind a medical diagnostic x-ray tube? If the x-ray tube was horizontally orientated and tightly collimated, and then exposed at 109 kVp and 3.2 mAs, can any x ray reach behind the direction of x ray (and thus behind the tube)?


Yes, the scatter from the patient goes out in all directions with the highest percentage being toward the x-ray tube. However, the x-ray tube will absorb most of the scatter that it intercepts due to the thick lead lining inside of the tube. That said, the x rays that are not absorbed by the tube will continue in the same direction. If one is standing behind the tube there will still be exposure from the x rays that are not absorbed by the tube, i.e., above and below the tube.

The best place to stand during an x-ray exposure is outside of the room (in a control booth) or behind a lead shield.

Joel Gray, PhD

Answer posted on 7 January 2015. 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.