Investigation of different gel dosimeters for quality assurance in radiation therapy

Abstract

High precision techniques in the treatment of cancer such as Intensity Modulated newlineRadiation Therapy (IMRT) and Volumetric Modulated Radiation therapy (VMAT) newlineinvolve the delivery of highly conformal doses using intensity modulated beams. newlineGelatin is a key ingredient in a gel dosimeter that provides the spatial matrix in which the dose newlineinformation is recorded when irradiated. The non-availability of high-purity gelatin newline(300 bloom) in India has been the driving force for the development of lower bloom newlinegelatin-based gel dosimeters. This was investigated for both radiochromic and polymer newlinegel dosimeters in this study. In this thesis, the characteristics of different types of gel dosimeters viz., newlineradiochromic LCV micelle gel, MAGAT polymer gel and FXGConv gel dosimeters were newlineinvestigated with special emphasis on FXGConv gel dosimeter with low bloom strength newlinegelatin addressing the ferric ion diffusion post-irradiation, reducing auto-oxidation and newlineimproving the optical transmittance of the gel dosimeter for applications in newlineradiotherapy. Due to the inaccessibility of the standard 300 bloom gelatin that is generally newlinepreferred for the manufacture of gel dosimeters, we have successfully researched the newlinefeasibility of using the available 240 bloom gelatin and established that this 240 bloom newlinegelatin with some enhancements is an adequate replacement for the 300 bloom gelatin. newlineWe therefore recommend the use of 240 bloom gelatin for the fabrication of gel newlinedosimeters in India as per the recipe suggested in the thesis. Although MR scanning and X-ray CT are the conventionally established read-out tools newlinefor gel dosimetry, in our investigations we observed that the X-ray CBCT could be used newlineas read-out for MAGAT gel dosimetry as it delivers satisfactory results. newlineHowever, further research work needs to be performed for implementation of X-ray newlineCBCT as the read-out tool for polymer gel dosimetry. newline