Positron camera for range verification of heavy-ion radiotherapy

A positron camera, consisting of a pair of Anger-type scintillation detectors, has been developed to verify ranges by using positron emitter beams. Each detector head is equipped with a NaI(Tl) crystal (diameter: 600 mm, thickness: 30 mm) for high detection efficiency. To get a low counting rate for this application, the electric circuit was designed for flexibility in measurement and analysis by software. The energy and position were calibrated for high measurement accuracy. A spatial resolution of 8.6 mm in FWHM within a +/- 50 mm region (field of view) and a linear response of a 0.3 mm standard deviation within a +/- 200 mm region were obtained. The camera was designed so as to measure the ranges within an accuracy of 1 mm under a dose limitation (about 100 mGyE) to reduce the safety margin for the irradiation field, and it met the required characteristics. (C) 2003 Elsevier B.V. All rights reserved.