Performance of the first ΔOSI microstrip dosimeter prototype in the characterization of a clinical accelerator

As the technology for medical radiotherapy and radiosurgery evolves, there is a growing need for dosimeters capable of measuring dose distributions on-line with submillimetre spatial resolution, both for facility commissioning and patient-related quality assurance. We have designed and built a high spatial resolution dosimeter based on silicon microstrip technology for characterization of small radiotherapy and radiosurgery fields. The aim is to provide relative dosimetry measurement with film-like spatial resolution, and to be able to observe the temporal evolution of the dose distribution. Beam test results of a 250 μm pitch, 128-channel prototype with X-rays in a clinical 6 MV accelerator are presented in this paper. The device has demonstrated good dosimetric capabilities when compared to reference measurements made with ionization chambers. Here, we evaluate the performance of our prototype in the steep dose gradient region produced by the collimator edge with respect to radiographic film and characterize a Multi-Leaf Collimator system used for Intensity Modulated Radiotherapy at the Weston Park Hospital.