NMR spectroscopy of saccharide-doped PAGAT dosimeters

he aim of this study was to investigate the chemistry of the PAGAT dosimeters when doped with saccharides and irradiated\u27 using NMR spectroscopy. Three batches of PAGAT gel dosimeters were manufactured. Two of them were doped with 20 % glucose and sucrose\u27 respectively. For each batch\u27 one sample was left unirradiated while the remaining samples were irradiated to different doses. After irradiation\u27 NMR spectra were obtained which clearly showed the composition of the dosimeter and the change in monomer concentration caused by irradiation. In addition\u27 it revealed that the saccharides did not directly participate in the chemical process before and during irradiation but the addition of saccharides resulted in a higher consumption rate of the monomers

Do saccharide doped PAGAT dosimeters increase accuracy?

To improve the dosimetric accuracy of normoxic polyacrylamide gelatin (PAGAT) gel dosimeters, the addition of saccharides (glucose and sucrose) has been suggested. An increase in R₂-response sensitivity upon irradiation will result in smaller uncertainties in the derived dose if all other uncertainties are conserved. However, temperature variations during the magnetic resonance scanning of polymer gels result in one of the highest contributions to dosimetric uncertainties. The purpose of this project was to study the dose sensitivity against the temperature sensitivity. The overall dose uncertainty of PAGAT gel dosimeters with different concentrations of saccharides (0, 10 and 20%) was investigated. For high concentrations of glucose or sucrose, a clear improvement of the dose sensitivity was observed. For doses up to 6 Gy, the overall dose uncertainty was reduced up to 0.3 Gy for all saccharide loaded gels compared to PAGAT gel. Higher concentrations of glucose and sucrose deteriorate the accuracy of PAGAT dosimeters for doses above 9 Gy.4 page(s

Feasibility study using MRI and two optical CT scanners for readout of polymer gel and Presage (TM)

The aim of this study was to compare the conventional combination of three-dimensional dosimeter (nPAG gel) and readout method (MRI) with other combinations of three-dimensional dosimeters (nPAG gel/Presage (TM)) and readout methods (optical CT scanners). In the first experiment, the dose readout of a gel irradiated with a four field-box technique was performed with both an Octopus IQ scanner and MRI. It was seen that the MRI readout agreed slightly better to the TPS. In another experiment, a gel and a Presage (TM) sample were irradiated with a VMAT field and read out using MRI and a fast laser scanner, respectively. A comparison between the TPS and the volumes revealed that the MRI/gel readout had closer resemblance to the TPS than the optical CT/Presage (TM) readout. There are clearly potential in the evaluated optical CT scanners, but more time has to be invested in the particular scanning scenario than was possible in this study