United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Question 175: A health care worker serves in a dual

nuclear medicine and radiology position. The worker wears

a dosimeter on the waist and a dosimeter at the collar.

During fluoroscopy procedures, which is the primary source

of exposure, the worker wears a lead apron that covers the

waist dosimeter, but not the collar dosimeter. Over the

course of a year, the worker receives a dose of 5.2 rem as

measured by the collar dosimeter and 1.7 rem as measured by

the waist dosimeter. (a) Has the individual been

overexposed? (b) Can licensees take credit for shielding

while monitoring the external dose component of the TEDE?

Answer: (a) Yes, the individual has received a dose in

excess of 10 CFR 20.1201 limits. The head and neck

constitute part of the "whole body", and in this case,

received the highest exposure. The collar dosimeter

measured a dose of 5.2 rem over the course of a year. If

the head and neck were not shielded, and if the collar

dosimeter was a measurement of the dose to the head and

neck, then the dose exceeded the limit of 5 rem TEDE.

(b) The licensee can only "take credit" for shielding if

it can be shown that the dose monitored behind the

shielding is an accurate measurement of the maximum deep

dose equivalent to the individual. Many shields used for

radiation protection do not cover all of the upper legs,

upper arms, and/or neck, and few if any shields protect the

head from external radiation. Therefore, few shields would

satisfy the conditions for credit. However, licensees

should use shielding as necessary to minimize the area of

exposure and keep doses ALARA. (Reference: 10 CFR 20.1201)

Page Last Reviewed/Updated Thursday, March 29, 2012