Answer to Question #2827 Submitted to "Ask the Experts"

I am a radiologic technologist working in a very busy operating room full-time. I am concerned about the protection of lead aprons varying in lead thickness. I just received a new lightweight lead apron with 0.35 mm Pb equivalent in the front and 0.25 mm Pb equivalent in the back. I am planning to have children in the near future and I am concerned about the protection this apron will give me. Will a 0.5 mm Pb equivalent apron better protect me? What are the kVp ranges attenuated for each thickness? Do lead aprons protect against low-level scatter radiation? What are the differences in protection from lead aprons in terms of direct beam attenuation and scatter radiation attenuation?

I am making the assumption that you know what radiation doses you are receiving and can put the following numbers in some context. If you wear your radiation badge on your collar outside a 0.5 mm equivalent lead apron, you can divide the collar badge reading by 22 to determine your whole-body radiation dose (National Council on Radiation Protection and Measurements Report 122). Or, you can use data from testing of lead aprons as follows. The following information includes actual test results at my institution. All measurements were done with the lead aprons in the primary beam using 100 kVp and 250 mAs at a distance of 40.

• Lead equivalence in apron—0.75 mm
  Transmission through apron—1.1%
   
• Lead equivalence in apron—0.6 mm
  Transmission through apron—2.2%
   
• Lead equivalence in apron—0.5 mm
  Transmission through apron—2.0-3.8% (ave of 3.2%)
   
• Lead equivalence in apron—0.35
  Transmission through apron—8.4%
   
• Lead equivalence in apron—0.25 mm
  Transmission through apron—10.4%

Let's take the 0.5 mm lead equivalent apron. On average, about 3.2% of the x rays get through the apron when exposed to the primary beam. So, if you were exposed to 100 mrem of radiation outside the apron, your body would be exposed to 3.2 mrem inside the apron. If you were wearing a 0.35 mm lead equivalent apron and exposed to 100 mrem outside the apron, your body would be exposed to 8.4 mrem inside the apron. The annual whole-body radiation exposure limit for radiation workers in the United States is 5,000 mrem. Since scatter radiation is a very low energy, there would be even less transmission through the apron. Since I don't know where you live, you can disregard the following if you live outside the United States. I believe most states, in their regulations, require 0.5 mm lead equivalent aprons. If an individual is primarily exposed from the front, there are exceptions to the lead equivalence in the back of the aprons. Some might not but if you live in the United States, you might want to check your State's local department of health Web site to see what its regulations say or talk to your organization's radiation safety officer or medical physicist just to be sure.

Kelly Classic
Certified Medical Health Physicist