Investigation of the effect of 2 different optimization algorithms on dose distribution in esophageal cancer radiotherapy

The dose - volume histograms (DVH) obtained from the plans prepared with VMAT technique in the Treatment Planning System (TPS) may differ from the plans obtained as a result of optimization. The intermediate dose optimization module, developed to eliminate this difference, provides better dose distribution, especially in inhomogeneous structures such as lungs. In the study, it was aimed to compare the effect of the use of the intermediate dose optimization module in patients located in the thorax, where inhomogeneity is more intense, especially in the lungs, with those located in the abdomen. The treatment plans created were normalized so that the target volume received 95% of the prescribed dose. In this thesis study, using Analytical Anisotropic Algorithm (AAA) dose calculation algorithm and AAA Intermediate dose optimization module and VMAT technique in Eclipse 15.6 TPS, treatment with both methods was used for a total of 20 patients with esophageal cancer, 10 of which were thoracic esophagus and 10 abdominal esophagus patients. plans have been prepared. For 20 patients, DVHs were determined in plans prepared first with the AAA dose calculation algorithm and then using the AAA Intermediate dose optimization module and the VMAT technique. Conformity index (CI) values, homogeneity index (HI) values and critical organ doses were compared. As a result of the thesis study, it was seen that the treatment plans created by including the intermediate dose optimization module gave better results for CI and HI values. Especially in thoracic esophagus patients where inhomogeneity is more intense due to the involvement of the lungs, it has been observed that the intermediate dose optimization module increases the plan quality and provides a more significant decrease in CI and HI values. A slight decrease was observed in critical organ doses.