Modelling the effect of a real-time dosimetry system in synchrotron X-ray microbeam radiation therapy

Full text: A solid-state quality assurance system for Microbeam Radiation Therapy is currently under development for in vivo dosimetry and pre-treatment quality assurance. As part of the system, a silicon microstrip, high spatial resolution dosimeter is scanned through the beam prior to treatment to provide a high degree of accuracy for quality assurance. Another component of the dosimetry system, a multi-strip silicon detector is placed upstream of the patient, acting as a transmission detector for real-time quality assurance. We investigate the effect the presence of the detectors on various parameters. Particularly, the corresponding dose ratio with depth in a water phantom is investigated. With the multi-strip detector placed in the peak of a MRT beam, the simulated depth dose measured within the water phantom was found to have an average decrease of 1.44 ± 0.15% (95% CI.). An array of rectangular microbeams were also simulated with the superposition algorithm of Siegbahn et al. [I], with lateral dose computed at a depth of I cm and along the central cross-beam axis in a water phantom. The decrease in peak dose with the multi-strip detector was determined as 1.41 ± 0.03% (95% CT.), agreeing with pencil beam results. Detailed results of Monte Carlo results for the peak to valley dose ratio and the microstrip detector and corresponding experimental results will be presented in the final paper. (I] E.A. Siegbhan et aI., Determination of dosimetrical quantities used in microbeam radiation therapy (MRT) with Monte Carlo Simulations. (author)