A TL-based anthropomorphic benchmark for verifying 3-D dose distributions from external electron beams calculated by radiotherapy treatment planning systems.

Initial results are reported of a Polish-Finnish project to verify electron dose distributions calculated by treatment planning systems (TPSs), CadPlan v.6.3.2 and Theraplan v.3.5, which use different electron beam dose distribution algorithms. Treatment of gross tumour volumes representing lung and parotid cancer was simulated in an Alderson anthropomorphic phantom with thermoluminescent detectors (TLDs) (Li(2)B(4)O(7):Mn,Si) placed at selected measurement points inside its volume. The observed discrepancy between relative values of dose calculated and measured by TLDs at each of the measurement points and those calculated by the different TPSs at the same points is discussed.

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 live 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.