Notes on the construction of solid-state detectors

Background and purpose: Soild-state detectors such as diodes and diamonds are useful radiation detectors, particularly for small field measurements, such as in stereotactic dosimetry [6] or in the small sub-field measurements required for intensity modulated radiotherapy (IMRT) [5]. In all small field measurements, positioning of the detector is critical. Generally it is assumed that the center of the sensitive volume of each solid-state detector is coincident with the geometric center of the outer casing. Patients and methods: X-rays were taken of four detectors (diamond, three types of diode) to determine the physical characteristics of each, particularly the position of the centre of the sensitive volume. Results: The results showed that the position of the centre of the sensitive volume is not always coincident with the geometric centre of a soild-state detector. Conclusions: The construction of a detector used for precise measurements should be investigated prior to use, by taking high resolution x-ray images. (c) 2006 Elsevier Ireland Ltd. All rights reserved.