Characterization of a Silicon strip detector for radiotherapy use

The present work aims at the rst characterization of a silicon strip detector to be used for quality assurance of intensity-modulated radiotherapy (IMRT) treatments. After a rst feasibility study, a new prototype has been designed and built in the framework of a collaboration between the University of Seville, the National Accelerator Centre (CNA Centro Nacional de Aceleradores, Seville, Spain), the Virgen Macarena University Hospital and the private company Micron Semiconductor Ltd. It is composed of two single-sided silicon strip detectors, mounted in a back-to-back conguration with the strips arranged along two orthogonal directions, and separated by a Kapton layer. This detecting unit can be housed in two dierent phantoms, a slab and a cylindrical one: in the former, the detector is placed orthogonally to the beam axis, in the latter, it is placed vertically, with the aim of obtaining on-line, measurement-based dose maps in the axial plane of a hypothetical patient. This work discusses the rst characterization of the new detecting unit, housed in the slab phantom and irradiated with a clinical linear accelerator in the 6 MV photon mode. Linearity, reproducibility, minimum dose threshold and leakage current have been analysed; a Geant4 simulation of the dosimetry system has also been carried out to gain further insight on the physical processes at play. The detector has then been calibrated and used to reproduce routine quality assurance hospital measurements; the comparison between the two shows remarkable agreement.