Abstract
This paper examines the difference in patient specific dosimetry using three different detectors of varying active volume, density and composition, for quality assurance of stereotactic treatments. A PTW 60017 unshielded electron diode, an Exradin W1 scintillator, and a PTW 31014 PinPoint small volume ionisation chamber were setup in a Lucy 3D QA phantom, and were positioned at the isocentre of an Elekta Axesse, with beam modulator collimator, using Exactrac and a HexaPODTM couch. Dose measurements were acquired for 43 stereotactic arcs, and compared to BrainLAB iPlan version 3.0.0 treatment planning system (TPS) calculations using a pencil beam algorithm. It was found that for arcs with field sizes [Formula: see text]mm, the properties of a detector have minimal impact on the measured doses, with all three detectors agreeing with the TPS (to within 5%). However, for field sizes [Formula: see text]mm, only the scintillator was found to yield results to within 5% of the TPS. The dose discrepancies were found to increase with decreasing field size. It is recommended that for field sizes [Formula: see text]mm, a water equivalent dosimeter like the Exradin W1 scintillator be used in order to minimise detector composition perturbations in the measured doses.
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