Answer to Question #12169 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment/Shielding — Lead Aprons

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

Q

When radiation from an x-ray source hits a lead apron, how would this affect the scattered radiation hitting one's face? I am assuming the x-ray energy would be significantly less once the lead apron has been hit, but I want to know about how much less it would be.

A

You are correct in assuming that the radiation dose from the scattered x rays would be less than from the direct x-ray beam. The dose from the scattered x rays will be affected by many factors, including the energy of the incident x rays (i.e., the peak kilovoltage [kVp] of the beam), the energy profile of the beam which varies depending on the material of the x-ray anode (e.g., tungsten or molybdenum) and the amount of filtration in the beam, the current or amperage of the beam, the cross-sectional area of the beam as it reaches the lead apron, the angle at which the beam strikes the apron, the lead-equivalence thickness of the lead apron, and other factors.

Needless to say, your question does not have an easy answer. Complex calculations using Monte Carlo techniques can provide estimates; however, the only way to determine the accuracy of such estimates is to make measurements of the incident x-ray beam and the scattered x rays and compare the results.

The good news is that the intensity of x rays scattered by 90 degrees (the scattering angle between the incoming beam and the upward angle to reach the face) will be less than one-thousandth of the intensity of the incident x-ray beam due simply to the physics of the scattering process. The scattered x-ray beam will also be of lower energy.

Edgar D. Bailey, PE, CHP

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 12 November 2017. 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.