The NOVO project - hybrid neutron/gamma-ray imaging for range verification in particle therapy

Particle therapy has proven highly sensitive range uncertainties, making online range verification essential. Here we present a status update on work by the NOVO collaboration investigating range verification through simultaneous imaging of prompt gamma-rays and fast neutrons. The proposed system is designed to offer high detection sensitivity to range shifts with a smaller footprint and cost than current state-of-the art systems, where the proton range can be calculated by imaging elastically scattered neutrons and gamma-rays emitted from patient tissues during treatment. Both the detector design and feasibility of the NOVO concept were investigated using Monte Carlo particle transport simulations, supported by an experimental characterization of candidate scintillator materials. The detector design was chosen to maximize the number of image-able detected events under clinical treatment conditions. The feasibility of the method was demonstrated using a real patient case chosen from the Cancer Imaging Archive. Results show that a range-shift sensitivity of 1 mm per spot is attainable for clinical proton intensities with detector resolution effects included. Our findings demonstrate the potential of particle treatment verification through simultaneous fast neutron and prompt gamma-ray imaging, present a design for such a system, and reinforce its suitability in clinical application.