Speaker
Description
Ultra-High-Dose-Rate (UHDR) / FLASH radiotherapy with proton pencil beams requires particle fluxes that saturate current clinical dosimetry, such as ionisation chambers. Before UHDR proton therapy can be clinically implemented, novel dosimetry techniques must be developed that reduce the uncertainty on delivered dose to within clinical accuracies. One promising solution is to image gas Beam Induced Fluorescence (BIF), where the photon yield and transverse profile can be combined to calculate an absolute dose. Using the AGOR cyclotron at PARTREC, a superconducting isochronous cyclotron capable of providing clinical beam energies and dose-rates well into the UHDR regime, we are assessing the feasibility of using BIF for dosimetry. We show that the photon yield of Nitrogen remains linear with dose even at UHDR beam currents and examine the gas pressure-dependence in the range from 1e-3 to 100 mbar. When calculating doses, the width of the fluorescent region is compared to the real transverse beam size and methods to remove the background neutron and gamma counts from the CCD image without significantly altering the photon yield are described. These experiments are the first step towards progressing towards minimally invasive optical beam monitoring with a BIF-based dosimetry device, incorporating both transverse profile and energy deposition measurements, that could be used in proton therapy.
Footnotes
t.w.a.fogg@umcg.nl
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