Target volume, normal tissue and peripheral dose measurment for cranio- spinal irradiation with VMAT

In this study, the doses to the target volumes and organs at risk in Cranio-Spinal Radiotherapy (CSI) for VMAT (Volumetric Modulated Arc Therapy, RapidArc), IMRT (Intensity Modulated Radiotherapy) and the conventional (Field in Field) techniques were compared. In addition, the accuracy of dose distribution calculated by the Treatment Planning System (TPS) for each technique was validated using TLD and Gafchromic film. Computerized tomography images of a humanlike phantom were obtained and uploaded to the TPS. These images were used to create the treatment plans. TLD and films were placed between slices of the humanlike phantom and phantom was radiated with 6 MV photon beams for each technique. Comparisons based on dose-volume histograms lead to the result that, the VMAT technique was found superior in order to giving prescription dose to the target volume. Compliance between calculated and measured dose values for in field regions were good but for heterogeneous regions like lungs the calculation-measurement difference was 8.4% and 12% in the testicles that are located out of the treatment field region. Comparison of calculated planar dose distribution and irradiated films show that, the lowest compliance was found in testicles region 87.2% and in lung region 94.4%. The results of this study present that RapidArc VMAT technique generates clinically acceptable dose distributions based on TPS calculations and is dosimetrically accurate based on TLD and film measurements.