Dosimetric comparasion of different volumetric treatment techniques retrospectively in gastric cancer

In this study, plans were made using 3B-CRT, IMRT, VMAT and HT techniques in 20 patients with RT who were diagnosed with gastric cancer and it was aimed to compare the doses of target volumes and critical organs dosimetrically. In addition, the Conformity Index (CI) and Homogeneity Index (HI) were compared for the target volumes. Six different treatment techniques were planned for each patient, including bVMAT (butterfly), VMAT 2 ark, YART5 (5-alan), YART7 (7alan), 3B-KRT (3-alan) and HT (Helical Tomoterapi) using CT images of patient streated in ourclinic. The VMAT and IMRT plans were prepared in Monaco TPS, the 3D-CRT plans in CMS XIO 5 TPS and the Helical Tomotherapy plans in VOLO TPS. VMAT plans and IMRT plans Monte Carlo algorithm, 3D-CRT and HT plans were prepared by using Superposition algorithm. Simultaneous integrated boost (SIB) technique in VMAT, IMRT and HT plans was used to define the target volume dose to be 54 Gy from 27 fractions and 54 Gy from 30 fractions in 3D-CRT plans. BED (Biological Equivalent Dose) calculations were made before the plans were made so that the tumor had the same biological equivalent effect. Doses distributions of PTV and risky organs (spinal cord, lungs, kidneys, small intestine, liver and heart) were evaluated with DVH and appropriate tests were made in SPSS program for statistical analysis. As a result, more homogenous and conformal dose distributions were obtained in VMAT 2 arc and HT techniques compared to other techniques. Best values in the low doses scattering and the maximum dose of the spinal cord were obtained from the 3D-CRT technique. In terms of critical organs, while the best protection is the HT technique for the lungs, heart and liver, VMAT 2 arc and bVMAT techniques provide the best protection for the kidney and small intestine, respectively. Key words: Gastric Cancer, Tomotherapy, VMAT, IMRT, 3B-CRT