Use of a LYSO-based Compton camera for prompt gamma range verification in proton therapy:
Journal
Medical Physics
Journal Volume
44
Journal Issue
12
Pages
6261-6269
Date Issued
2017
Author(s)
Abstract
PURPOSE: A Compton camera (CC), which measures prompt gammas (PGs) emitted during proton therapy, is a potentially useful imaging device for proton range verification. The aim of this study was to evaluate how well the reconstructed PG images obtained from various two-stage CC configurations reproduce the distal falloff of the PG emission. METHODS: We conducted Monte Carlo simulations to evaluate different two-stage CCs positioned orthogonal to a proton pencil beam irradiating a water phantom. The results were compared with those obtained for a three-stage CC. In particular, all detectors were made of lutetium-yttrium orthosilicate (LYSO) crystals. RESULTS: We found that: (a) the position resolution of the detector led to more uncertainty in predicting the depth of maximum emission and distal falloff positions than did the energy resolution of the detector; (b) reducing the thickness of the absorber detector reduces the effect of position resolution on the quality of reconstructed images and improves falloff position estimates; (c) incomplete absorption of PGs can be filtered by restricting incident gamma energies to known PG energy spectral peaks; and (d) there is greater bias and less accuracy in predicting distal falloff positions with the three-stage CC compared with the two-stage CC. CONCLUSIONS: This study demonstrates the feasibility of using various CC designs and event selection methods to improve the imaging of PG rays. In our designed two-stage CCs, the thin LYSO-based absorber can provide better predictions of the distal falloff positions than the thick one. Compared to three-stage CCs, two-stage CCs are less biased and provide more accurate range verification.
Publisher
John Wiley and Sons Ltd
Type
journal article