Dosimetry of a portable in vivo x-ray fluorescence system using EBT3 radiochromic film

Purpose. In vivo x-ray fluorescence is a non-invasive analytical technique for determining trace and toxic element exposures. In this work we measure the dose for a portable handheld x-ray system (pXRF). Materials and Methods. We used EBT3 radiochromic film calibrated with a clinical orthovoltage unit for absolute dose measurement. Films were placed on a human phantom and irradiated with the Tracer III-SD pXRF at tube potentials of 40 and 45 kVp with various levels of filtration. Results. Using settings that result in the best detection limits, the highest absorbed point dose to the skin was 0.3 Gy, the equivalent dose to a 1 cm² area was 54 mSv, and the whole-body effective dose was less than 1 μSv for a standard 3-min in vivo measurement of strontium or lead. Recent work has demonstrated that 1 s and 30 s measurements are feasible for bone strontium measurements, which would lead to significantly lower doses. Conclusions. Our results are in agreement with a previous dosimetry study of another portable x-ray device and indicate that it is safe for in vivo measurements of elements such as strontium and lead, only after appropriate dose validation and with appropriate beam filtration in place. (paper)