TL detectors in verification of planning system’s for conformal and VMAT techniques of X-ray external beam

Introduction X-ray beam is the most widely used source for external beam radiotherapy. The dosimetry of these beams is controlled by thermoluminescent detectors (TLD) due to their small size and wide range of measured doses. Purpose This work presents the evaluation of the absorbed doses in TLD and calculated in treatment planning systems for conformal and VMAT techniques. Radiotherapy Department Silesia Oncology Center routinely uses computerized treatment planning systems Oncentra MasterPlan and Monaco in dose calculation in the patient’s body treated with external X-ray fields. The evaluation of the impact of preliminary conditions to the dose distribution in clinical and QA cases can be found in many papers. The way of the calculation correctness verification in heterogeneous medium is different for each radiotherapy department. Materials and methods There were prepared three different treatment plans for cancer therapy in pelvis, chest and head areas with the use of 6 MV beams in conformal and VMAT techniques. Dose calculations were performed with the Colapsed Cone Convolution and the Monte Carlo algorithms for anthropomorphic phantom and were compared with dose measured by calibrated TL detectors placed inside the phantom during irradiation. Results The results for all cases fulfill expectations for required accuracy in the treatment planning system regarding inhomogeneity correction. Conclusion It was observed that the dose uncertainty values are 5–10% for the area of the cancer tissue. These points are placed in the region with the high dose values and a high gradient of dose.