Assessment of out-of-field radiation doses for high dose per pulse intraoperative electron beam radiotherapy using TLD-100

Abstract

PurposeThis research aims to assess the out-of-field surface doses for different combinations of electron energy, applicator size, and distance from the applicator wall of high dose-per-pulse IntraOperative electron Radiation Therapy (IOeRT) using thermoluminescent dosimeters (TLDs). Materials and methodsThe out-of-field doses for various combinations of IOeRT electron beam energy/applicator size were measured using ionometric dosimetry. The calibrated LiF:Mg,Ti dosimeters (TLD-100) were used to make the measurements. TLD results were benchmarked using an Advanced Markus chamber and a polymethyl methacrylate slab phantom. TLDs were read out using a HARSHAW (type 4000) manual TLD reader. ResultsThe TLDs received out-of-field absorbed doses ranging from 0.033 to 0.545 mGy/MU depending on the applicator size, electron energy, and distance from the applicator's outer wall. The mean discrepancies between TLDs and Advanced Markus ion chamber measured data were about 1.82% in the PMMA slab phantom at a depth of maximum dose for each electron energy. ConclusionThe skin surface dose can be significant during IOeRT. The maximum out-of-field doses have occurred at high electron beam energy and closer distances around the applicator wall. TLD can measure the skin's dose level according to its good agreement with the reference Advanced Markus dosimeter. The TLD-100 can be used as a reliable dosimeter for intraoperative radiation dosimetry.