The comparison of dynamic and static multi segments techniques in intensity modulated radiotherapy

In Intensity Modulated Radiotherapy (IMRT), dose intensity is changed with multi leaf collimator (MLCs) in a complicated way for all fields. For this reason, it is neccesary to dosimetrically verify IMRT plans. The main purpose of this thesis is comparing dynamic multisegmented plan with static multi segmented plans in different segment levels (5,10 and 20) for IMRT plans of 10 nasofarengial cancer patients in Eclipse treatment planning system by Varian lineer accelerator in respect to target volume, organs at risk (OAR), monitör unit (MU) values and irradiation time. The second purpose is verifying the accuracy of QA plans which is constituted with same patient group for all plans. Obtained plans are compared by using Dose Volum Histogram (DVHs). IMRT QA plans are constituted. The dose fluence maps of these plans are measured with Electronic Portal Imaging Device (EPID). Gamma analysis of measured and calculated dose fluence maps are calculated by EPIQA with %10 filtration according to %3DD-3DTA criterias. When the plans constituting for all patients are compared doses of both target volume and OAR, they were similar. When MU values of the plans were analyzed, MU values of SMLC plans are calculated %25 less than DMLC plans. With regard to irradiation times, DMLC plans are taking less time. Dose fluence maps of reference DMLC plans are compared with SMLC QA plans with %10 filtration. Than, it is observed that when segment levels are increased, gamma index values are increased too and in 20 segment level it is compatible with %97. When measured and calculated dose fluence maps of QA plans are compared, DMLC plans are resulted %95 gamma index and SMLC5 plans are resulted %86, SMLC10 %94, SMLC20 %97. Consequently, in the treatment of head and neck cancers varied advantages of SMLC and DMLC techniques are observed and might be applied in secure. Keywords: Static IMRT, dynamic IMRT, gamma analysis, Treatment planning systems.