Geant4 and ANU Auger-electron cascade Monte Carlo model comparison

Full text: The extreme radiotoxicity of Auger electrons and their exquisite capacity to irradiate specific molecular sites has prompted scientists to extensively investigate their radiobiological effects. In radiotherapy Auger-electron emitting radionuclides are of great interest because of their short range, which is a very important feature to protect normal tissue adjacent to the targeted tumour. This unique feature offers some distinct advantages compared to the more commonly used long-range beta electrons, such as a reduced cross-fire irradiation of non-target healthy cells and a higher ionisation density within the immediate vicinity of the decay site, which is generally associated with high(er) biological effectiveness. Auger-emitting radionuclides have shown very promising effects in vitro and in vivo in animal studies over the last decade. Emission spectra of Auger-electron emitting radionuclides are essential for dosimetric calculations to quantify the biological damage delivered to the target. In the past three decades several authors published calculated emission spectra of selected radionuclides using either deterministic or Monte Carlo computational methods. Geant4.10.04 extended example (radioactive decay 01) have been used in this study. We compared results obtained with Geant4 and the ANU model to other data sets for I-123, I-124 and I-125. Yield ratios of Geant4 and other data sets to ANU are plotted. Performance of Geant4 and a recently developed Monte Carlo model of Auger cascades have been compared. Good agreement with the published data is found. (author)