Development, characterization and radiation dosimetry evaluation of Bovine gelatin crosslinked with Gum Arabic Aldehyde as brain phantom gel material in radiation therapy

Abstract

Brain phantom gel materials are of critical importance for accuracy of dosimetry, treatment planning and quality assurance in radiotherapy. Development of reliable and realistic phantoms enhances improved radiotherapy practices. Gel dosimeters have unique property to record radiation dose distribution in three dimensions. Polymer gels also have added advantages for brachytherapy dosimetry. Objective of the study was to develop an alternative polymeric gel material equivalent to human brain for conducting radiation dosimetry studies in radiotherapy. Hydrogel prepared from gelatin and gum arabic aldehyde was used to develop a brain phantom gel material for radiation dosimetry in radiotherapy. The results of comparative studies with G-GAAB gel strongly suggest, the gel can successfully be utilized as a brain equivalent material for radiation dosimetry in place of standard water phantom by measuring (a) CT number values (b) mass attenuation coefficient values at two X-ray energies used in radiation treatment (c) absorbed dose values at different depths for various setup conditions. The midrange CT number values inside gel material and that of human brain measured from CT images were 25.5HU and 25HU respectively with a variation of 2%. The mass attenuation coefficients for brain, water and gel material at 6MV photons were 0.0275cm2/g, 0.0280cm2/g,0.0270cm2/g and for 15MV photons, the attenuation coefficients were 0.0192cm2/g, 0.0190cm2/g and 0.0180cm2/g respectively. The percentage deviation of all measurements of absorbed dose values in gel phantom material, compared with the values of standard water phantom at various radiation dosimetry setup parameters, is less than 2%.