Answer to Question #12169 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
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.
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