Experimental Validation of Filtered Interaction Vertex Imaging for Intra-Fraction Relative Range Verification in Heavy-Ion Therapy

Abstract

The growing societal burden of cancer necessitates improvements in the safety and efficacy of treatment. Scanned heavy-ion therapy provides precise and highly conformal radiation treatment of tumours, but it is difficult to ensure accurate dose delivery due to uncertainty surrounding ion beam range in tissue. Relative range verification via filtered interaction vertex imaging could monitor the spacing of each treatment beam endpoint, ensuring full and consistent tumour coverage. To validate this method, twelve \(^{16}O\) beams of differing energy irradiated a 40 mm poly-(methyl methacrylate) phantom. Secondary particles were monitored using position-sensitive silicon detectors, and used to reconstruct the depth distribution of beam-phantom nuclear reactions. Comparison of logistic fits to the distal edges of these distributions computed the range shift between two energies to sub-millimeter precision with a standard deviation of the mean of 220(10) μm, validating filtered interaction vertex imaging as a candidate for clinical high-performance range verification.