CyberKnife® Robotik Radyocerrahi Cihazında MAGIC Polimer Jel Dozimetre İle Küçük Alan Dozimetrisinin İncelenmesi

Abstract

ENKAVİ, M.F. Investigation of Small Field Dosimetry with MAGIC Polymer Gel Dosimeter in CyberKnife® Robotic Radiosurgery Device. Hacettepe University Institute of Health Sciences, MSc. Thesis in Radiotherapy Physics Program, Ankara, 2018. Dosimeters with having small sensitive volume and tissue-equivelancy are preffered in small field dosimetry. These dosimeters are generally ion chambers, solid-state dedectors which is giving point dose information and providing 2D dose distrubition, such as film dosimeters. The only dosimeter that providing 3D dose distrubition is gel dosimeters. In this thesis study, using with CyberKnife robotic radiosurgery treatment device and its 5, 7.5, 10, 12.5, 15, 20, 25, 30, 60 mm collimators, small field measurements taken by microDiamond dedector, SRS Diode dedector, PinPoint ion chamber, GafChromic EBT3 film dosimeter and MAGIC polymer gel dosimeter. Beam profiles at 15, 50, 100 mm depth and percent depth dose, relative dose factors are measured with all dosimeters. Penumbra widths, full width at half maximums, maximum dose depths and relative dose factors of MAGIC polymer gel dosimeter compared with other dosimeters and suitibility of gel dosimeter is investigated. MR images of gel dosimeters are taken with 1.5T MR device, at TR 4040 ms and TE 50-100-150-180ms with 1.5 mm slice thickness. MR images analized with PolyGeVero software. PDD and output factors were found compatible with microDiamond and SRS diode detectors. When penumbra, FWHM and beam flatness values were compared with all other dosimeters, unacceptable differences were observed. MAGIC polymer gel dosimeter FWHM values showed an expansion from all other dosimeters at a depth of 15 mm, and a narrowing at a depth of 100 mm. The polymer gel dosimeter should be cautiously used in small areas due to incompatibility with the reference dosimetry results and uncertainty it has.