Dose response evaluation of a low density anoxic polymer gel dosimeter using MRI

Abstract

Background: The human body contains of differentssues and cavies with different physical and radiological properes. Most important among these aressues and cavies that are radiologically different from water, including lungs, sinuses and bones. Gel dosimetry provides a unique feature to display dose distribuons occurring in clinical radiaon therapy in three dimensions. Materials and Methods: The low density polymer gel dosimeter is composed of 12% gelan, 5% methacrylic acid, 0.15% sodium dodecyl sulfate, 10 mM THPC, and approximately 83% ultrapure deionized water. Post- preparaon irradiaonme for all samples was 5 hr. Theme between irradiaon and scanning for all gels experiments was 18 hr. The gel dosimeters were imaged using a 1.5 T clinical MRI scanner in a transmi.er/receiver head coil. Results: There was a linear correlaon between the doses and R2 responses from 0 to 12 Gy. However, above the 14 Gy probably due to saturaon and or consumpon of the monomers the dose response was reduced. The low-density gels had a mass density between 0.35 and 0.45 g.cm -3 and the CT values of about -650 to -750 Hounsfield units. These values are close to those of the normal human lungssue, which ranges from -770 to -875 Hounsfield units. Conclusion: Increasing the gel temperature during rotaon in the household mixer and probably reacons between the gelan-free radicals and monomers led to a higher R2-background response.