Validation of a radiotherapy treatment planning system using an anthropomorphic phantom and MTS-N thermoluminescent detectors

A treatment planning system (TPS) was validated in conditions of simulated radiotherapy (RT) of an anthropomorphic tissue-equivalent phantom. Individually calibrated solid MTS-N (LiF:Mg,Ti) detectors were placed within the treatment volume in this phantom which was then repeatedly irradiated by external ⁶⁰Co or 6 MV X ray beams. On the basis of TLD-measured depth-dose curves for the two beams, the relative accuracy of determining dose (of the order of 1 Gy) at five depths in a water phantom is about 0.4-0.6%. In the volume of interest representing the target volume, the relative standard difference between the calculated and measured dose values ranged between 1.3% and 2.2% for the ⁶⁰Co and 6 MV X ray beams, respectively. The TPS-calculated uniformity of irradiation of that volume is within 1%. While fraction-to-fraction repeatability was within 1-2%, systematic underexposure around the reference point, by 2-3%, was found in two consecutive exposures by sets of both beams.