Yoğunluk Ayarlı Radyoterapi (Yart) Tekniğinde Yaprak Hareketlerinin Tekrarlanabilirliginin David İn-Vivo Dozimetrik Sistemi ile İncelenmesi

Abstract

Intensity Modulated Radiotherapy (IMRT) is an advanced high precision method which gives high doses of radiation to a tumor or a targeted area on the body. With patients treated by the IMRT technique, the transmission of the dose is provided by leaf movement. Fort his reason, the correct placement of the leaves on the correct time is very important in terms of the success of the treatment. DAVID (Device for Advanced Verification of IMRT Deliveries) in-vivo dosimetric system, can confirm the errors that can result from the leaf movement. In this thesis, subjects are 10 IMRT receiving patients (5 head and neck, and 5 prostate). The 10 IMRT treatments have been implemented on a Varian DHX lineer accelerator and were approved by ‘’Dynamic’’ and diffrent intensity level (5, 10, 20) ‘’Static’’ Multi Leaf Collimators and gone through Electronic Portal Imaging Device (EPID) quality control. In the first day of their treatment, the positioning information of the leaf movements were acquired through DAVID which were installed on the head of the linear accelerators. In the later weeks of the treatment (1. , 2. , 3. and 4.), same procedure was applied and the changing of the positioning of the leaves were observed by comparing the two data. As for the Static Multi Leaf Collimators, each intensity effect on the positioning of the leaves were observed. For the four different multi-leaf collimator techniques, the ''Total Deviation'', '' Beam Average Deviation'', ''Segment Average Deviation'' values were compared through the DAVID software. In order to estimate the p-value of the Friedman test (α=0.05), SPSS 17.0 Statistical Software was used for each technique. The comparison of the leaf positioning information with the IMRT plans executed on the 10 patients with the 1. , 2. , 3. and 4. week values for the four different MLC techniques taken as references, has shown the ''Total Deviation'', ''Beam Average Deviation'', and ''Segment Average Deviation'' Dynamic, Static; intensity level 5, 10, 20 numbers respectlvely as: %1, %2, %3 and %5. The difference has became more apparent as the segment count increased by the Static technique has complicated the MLC movements. Due to the fact that the p values between the fractions within the DAVID system have been above the accepted statistical significance levels, the changes of the leaf movements between the factions have been limited.