Development of BANG-3?? Polymer Gel Dosimetry System in Small Radiosurgical Fields

Abstract

In this study we focused on relative output factor, radiation field profile and three-dimensional dose distribution measurements of small radiosurgical fields using BANG-3r polymer gel. Polymer gel phantom was irradiated by 5 and 30 mm radiosugical beam size with 6 MV radiosurgery beam. MR scan was performed under the condition of same slice thickness and different resolutions. Output factor measurements with the PinPoint ion chamber, diode and EBT are compared with BANG-3r polymer gel. We used a spherical phantom filled with BANG-3r polymer gel to measure 3D dose distributions. The irradiated phantom was scanned with an MRI scanner. Relative otput factor and dose distribution were obtained by calibrating the polymer gel and the spin-spin relaxation rate of the magnetic resistance signal. Results showed that polymer gel output factor agreeds with diode as a reference 30 mm beam size. The gel dosimetry was useful tool available for overcome tissue-equivalence, beam perturbation implications, volume averaging and positioning uncertainties in small radiosurgical dosimetry. In three-dimensional dose distribution, the MRI artifacts cause a geometrical distortion of less than 2 mm and less than 10% change in the distribution. The gel dosimetry has the potential to qualitatively characterize the relative output factor, beam profile and the dose distributions.