Answer to Question #14090 Submitted to "Ask the Experts"

Category: Medical and Dental Equipment and Shielding — Lead Aprons

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

Q

I see in the NCRP Reports specific to radiography practices (medical, dental, veterinary, etc.) that lead/lead-equivalent aprons are recommended, however, the lead/lead-equivalent thickness is not provided. I see in other publications that 0.5 mm and 0.25 mm are the "standard." Is there a reference to determining and prescribing these specific thicknesses? I see in the NCRP Reports specific to radiography practices (medical, dental, veterinary, etc.) that lead/lead-equivalent aprons are recommended, however, the lead/lead-equivalent thickness is not provided. I see in other publications that 0.5 mm and 0.25 mm are the "standard." Is there a reference to determining and prescribing these specific thicknesses?

A

I'm not certain where the historical values for recommended lead thickness arise, however, minimum lead or lead equivalent thickness requirements are specified in various state regulations. It is common for states to require a minimum of 0.25 mm of lead, while others require 0.5 mm.

I noted that your email address is with the US Air Force, and their requirements are as follows:

The AF used to have a standard in AFI 48-148. However, the current AFMAN 48-148, which supersedes the previous versions, has no standard beyond stating that PPE (including lead shielding) can be used to meet as low as reasonably achievable (ALARA). The old standard (dated 14 December 2015) had stated the following:

4.8.1.6. Leaded protective aprons shall be worn in the fluoroscopy room by all medical and support staff during all fluoroscopy procedures. Note: Radiation PPE normally ranges from 0.25-1 mm lead equivalent; a qualified expert (e.g., medical physicist or bioenvironmental engineer, as defined in the Glossary) shall specify and recommend all protective shielding for the specific modality.

4.5.5.1. Gonadal shielding using at least 0.5 mm lead equivalence shall be used whenever potentially procreative individuals are likely to receive direct gonadal radiation in an exam or treatment or the primary beam is within 2.5 cm of the gonadal area.

4.5.5.3. The lens of the eye should be shielded with a least 2 mm lead equivalence during tomographic procedures that include the eye in the useful beam (not required for PA projections).

As a medical health physics consultant, we expect to see our facilities meet the minimum requirements for the state that they are located in. If we are asked for a recommendation, we recommend a minimum of 0.5 mm lead or lead equivalent. That way, everyone is using the same standard, while maintaining the spirit of ALARA.

Kennith "Duke" Lovins, CHP
Michael Cox, DABR

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.
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