Verification of evaluation accuracy of absorbed dose in the dose-evaluation system for iridium-192 brachytherapy for treatment of keloids

Abstract

Ir high-dose-rate superficial brachytherapy (HDR-SBT) has been delivered as a postoperative radiotherapy to prevent recurrence of keloids in Nippon Medical School Hospital. However, extra radiation exposure for organs at risk is a concern because high-energy gamma rays penetrate more deeply than electrons at the energies typically used for therapy. Therefore, a system which can evaluate absorbed dose in the affected area and radiation exposure to tissue and organs based on the actual geometry in HDR-SBT was developed using the PHITS Monte Carlo code and a MIRD-5 phantom in our previous work. In this study, the absorbed dose was measured in a simple geometry using a waterequivalent phantom and radio-photoluminescence glass dosimeters to verify the evaluation accuracy of absorbed dose calculated by the developed system. We find that, accounting for the transit dose component and the energy dependence analytically, the calculations by PHITS underestimate the absorbed dose by 10.2% to 19.0% (average 15.5%±1.9%) compared to the measurements. The sensitivity-correction procedure was considered to be the main reason for the difference between the measured and calculated absorbed dose of the dosimeters.

Quantitative study on dose distribution of Freiburg flap for keloid high‐dose‐rate brachytherapy based on MatriXX

“…But for superficial skin tumors, the FF applicator placed on the skin surface cannot provide sufficient scattering conditions 8 . Several studies have been carried out to evaluate the dosimetric effect of incomplete scattering conditions 9–13 . Jayakody reviewed the dosimetry procedure to verify the dose in HDR brachytherapy 14 .…”

“… 8 Several studies have been carried out to evaluate the dosimetric effect of incomplete scattering conditions. 9 , 10 , 11 , 12 , 13 Jayakody reviewed the dosimetry procedure to verify the dose in HDR brachytherapy. 14 The TG‐186 report proposed a model‐based dose calculation algorithm 15 and several commercial TPS have updated their program.…”