In-Phantom Peripheral Organ Doses from Prostate Irradiation Using 18 MV External Beam Radiotherapy Measured with 6LiF:Mg,Cu,P 7LiF:Mg,Cu,P Glass-Rod TLDs

摘要

A radiation dosimetry technique based on pairs of LiF:Mg,Cu,P and ~7LiF:Mg,Cu,P glass-rod TLDs was developed for measuring peripheral photon and neutron doses in the humanoid Rando phantom as a result of prostate irradiation using the 18 MV three-dimensional conformal radiotherapy (3D-CRT). The peripheral doses for different organs were estimated from TLD measurements and the risks of radiation-induced second malignancy were estimated using the competitive risk and linear no-threshold models. It was observed that following 80 Gy prostate irradiation using 18 MV 3D-CRT technique, both photons and neutrons doses ranged from approximately 97 mSv (in thyroid) to 807 mSv (in colon). Using the competitive risk model, the estimated risk of second malignancy was found to be ranging from 0.5% (for lungs) to 3.3% (for colon). Due to low doses (<2 Gy) exposure, estimation of the risk of second malignancy using the linear no-threshold model resulted in similar values as obtained with the competitive risk model. In conclusion, 6LiF:Mg,Cu,P and 7LiF:Mg,Cu,P glass-rod TLDs can be used in pairs to enable determination of photon and neutron doses simultaneously in a Rando phantom and to evaluate the impact of prostate cancer irradiation with high-energy (18 MV) 3D-CRT technique on the risk of second malignancy in various organs.