TLD measurement to investigate the bolus effect on skin dose in total body irradiation with helical tomotherapy

The aim of this study is to investigate the skin dose of total body irradiation (TBI) with Helical Tomotherapy and the need to use a bolus to achieve an adequate skin dose. To simulate the RANDO phantom geometrically, arms and legs created from rice were added to the RANDO phantom and it was immobilized in a vacuum bed. Computed tomography (CT) images of the lower and upper parts of the phantom with a slice thickness of 3 mm were acquired with and without bolus. Fifteen thermoluminescent dosimeters (TLDs) were placed on the skin line of the RANDO phantom. Treatment plans were prepared, and the phantom was irradiated both with and without bolus by the Helical Tomotherapy technique. Results of the measurements and treatment planning system (TPS) doses were compared by the non -parametric Wilcoxon signed -rank test. All procedures were repeated three times and results were evaluated. At the end of the study, it was proven that even when no bolus is used, the skin receives an adequate dose in TBI with Helical Tomotherapy while achieving homogeneous dose distribution and saving critical organs at the same time.