Akademik Veri Yönetim Sistemi
INTERNATIONAL CONFERENCE ON RADIATION APPLICATIONS (RAP 2021), 6 - 08 Eylül 2021, ss.73-74
Purpose. In total body irradiations, it becomes hard getting homogenous dose distribution due to inhomogeneous body shape and tissue density variations. The main goal of radiotherapy is to save critical organs while achieving a homogeneous dose distribution at target volume. Tomotherapy and Volumetric Modulated Arc Therapy (VMAT) are new and the most effective technologies used for total body irradiations. The purpose of this study is to compare critical organ doses, Planning Target Volume (PTV) coverage and dose homogeneity on Tomotherapy and VMAT technics for TBI treatments. Materials and Methods. In this study, the arms and legs were added to the male phantom using rice to simulate the whole body geometrically. The male phantom with arms and legs was immobilized by a vacuum bed and 3 mm CT images were received using Philips Big Bore CT. CT images were received as the upper and lower part of the body and used for contouring in the treatment plans. The entire body, lungs, lens, and kidneys were contoured with 3 mm margin and PTV is created. The prescribed dose was 12 Gy at a coverage of 90% PTV. The maximum dose limits for critical organ doses were 8 Gy for the lung, 7 Gy for the liver and 4 Gy for the lenses. TBI plans were prepared on VoLo 2.0.4 Treatment Planning System (TPS) for Tomotherapy and Eclipse 15.6 TPS for VMAT. The evaluation of the plans was made by comparing the homogeneity index (HI) and the doses taken by the critical organs. Results. At the end of this study, it was seen that saving critical organs and achieving desired dose distribution are possible for both Tomotherapy and VMAT in TBI treatments. HIs were 0.16 for tomotherapy and 0.29 for VMAT. Mean lung doses (right/left) were 7.61 Gy/7.70 Gy for Tomotherapy and 9.09 Gy /9.23 Gy for VMAT. Mean kidney doses (right/left) were 6.7 Gy/6.51Gy for Tomotherapy and 6.46 Gy/6.43 Gy for VMAT. Lens doses were similar and below 4 Gy. Conclusions. In conclusion, although both treatment techniques can be applied, more homogeneous dose distribution and lower lung doses are obtained with the Tomotherapy technique. When it comes to deciding for the TBI treatment method, some other crucial points must be considered. Treatment time, planning time, repeatability of treatment, and being comfortable for both patient and team are the other important points.
Keywords: Helical Tomotherapy, VMAT, total body irradiation