Measurement of entrance skin dose (ESD) by TLD dosimeters and its comparison with treatment design systems in GYN brachytherapy

Careful treatment planning of brachytherapy is an essential aspect of cancer treatment. The aim of this study was to evaluate the accuracy of calculations of treatment design system in GYN brachytherapy by BEBIG-60Co device by performing entrance skin dosimetry (ESD) using TLD dosimeters. For this study, 11 GYN cancer patients selected for brachytherapy to measure skin surface dosimetry. Finally, a comparison was made between the dose calculation from the treatment design system and the dose measured by the TLDs. In about 90% of the cases, there was a good agreement between the treatment dose calculation and the TLD measurement (taking into account the 5.5% uncertainty for the TLD). Increasing the dose in the anterior position of patients 5 and 11 can be due to the displacement of the applicator in the direction of length. For patient No. 8, moving the Ooid applicator to the right has led to an increase in dose and a decrease in the right and left directions. Several factors, such as the movement of markers on the patient's skin and the movement of applicators during patient transfer between imaging and treatment rooms, cause differences in the dose of TLDs compared to the dose of TPS. Therefore, the method of dosimetry of the skin surface can be a suitable method to confirm the accuracy of the dose in the treatment of GYN HDR.