[How conservative is routine personal dosimetry monitoring in diagnostic radiology?]

Dose values obtained by official personal radiation exposure monitoring are often considered equivalent to the effective dose of a person. This paper provides estimates of the extent of deviation between the two dose concepts under various conditions.

Doses for patients and personnel were measured using thermoluminescence dosimeters for five different geometries at three work settings in a radiology department. Patients and personnel were simulated with anthropomorphic phantoms. Different types of protective clothing as well as permanent protection shields were considered in the calculations.

Dose values obtained by official personal dose monitoring are conservative only for specific radiation protection situations. With state-of-the-art personal protective equipment (wrap-around style lead apron with thyroid shield), the ratio between effective dose and personal dose varies between 0.6 and 1.25. Without thyroid protection the official personal dose systematically underestimates the effective dose: for protective clothing with 0.5 mm lead equivalent without thyroid shielding, the effective dose exceeds the personal dose by factors between 1.7 and 3.1. If protective clothing with lead equivalent 0.35 mm is used, this factor varies between 1.1 and 1.82.

The official exposure monitoring algorithms for estimating the effective dose for occupationally exposed personnel are not always appropriate for typical situations in diagnostic radiology. Improved dose measurement protocols should avoid underestimation of the effective dose. The results presented herein provide an opportunity to derive more realistic effective dose values from personal dosimetry measurements.