Wide dynamic dose range of VIPAR polymer gel dosimetry

In this work the extent of the linear dose response and the dynamic dose ra nge of N-vinylpyrrolidone-argon based (VIPAR) polymer gels were investigate d. VIPAR gels were irradiated using a 6 MV linear accelerator up to 60 Gy a nd a Nucletron microSelectron Ir-192 HDR brachytherapy source to much highe r doses to cover a dose range of two orders of magnitude. They were then MR scanned at 1.5 T to obtain T-2-maps. VIPAR gel measurements obtained from the two irradiation regimes were calibrated against ion chamber measurement s and dose calculations derived using the AAPM TG-43 protocol respectively. A satisfying agreement between the calibration results derived using the 6 MV x-rays and the Ir-192 source was found for doses up to 60 Gy, implying that the response of the VIPAR gels is independent of photon energy and dos e rate. A linear R-2 dose response up to similar to 40 Gy and a dynamic dos e range up to at least similar to 250 Gy were observed. VIPAR gel dose meas urements derived using the monoexponentially fitted brachytherapy calibrati on data were found to be quite accurate.