A New Method to Reconstruct in 3D the Emission Position of the Prompt Gamma Rays following Proton Beam Irradiation

Abstract

A new technique for range verification in proton beam therapy has been developed. It is based on the detection of the prompt γ rays that are emitted naturally during the delivery of the treatment. A spectrometer comprising 16 LaBr3(Ce) detectors in a symmetrical configuration is employed to record the prompt γ rays emitted along the proton path. An algorithm has been developed that takes as inputs the LaBr3(Ce) detector signals and reconstructs the maximum γ-ray intensity peak position, in full 3 dimensions. For a spectrometer radius of 8 cm, which could accommodate a paediatric head and neck case, the prompt γ-ray origin can be determined from the width of the detected peak with a σ of 4.17 mm for a 180 MeV proton beam impinging a water phantom. For spectrometer radii of 15 and 25 cm to accommodate larger volumes this value increases to 5.65 and 6.36 mm. For a 8 cm radius, with a 5 and 10 mm undershoot, the σ is 4.31 and 5.47 mm. These uncertainties are comparable to the range uncertainties incorporated in treatment planning. This work represents the first step towards a new accurate, real-time, 3D range verification device for spot-scanning proton beam therapy.

Range Verification by Means of Prompt-Gamma Detection in Particle Therapy 1

“…Panaino et al make use of coincidence between two consecutive gamma-rays from the deexcitation of 16 O (2.75 MeV followed by 6.13 MeV with 25 ps decay time) to reconstruct in 3D the emission vertex position, by means of a nearly-4π multi-detector of high temporal resolution [59]. This is made possible since the two gamma emissions occur at the same location.…”

Monte Carlo methods for device simulations in radiation therapy

“…The emission characteristics of the prompt gamma was investigated and prompt gamma detection with an ideal condition, according to the paper, was simulated. Panaino et al recently reported 3D reconstruction algorithm for the prompt gamma images with Geant4-based simulation of the detection systeam and 180 MeV proton beams that were delivered to water phantom (Panaino et al 2019). They located the proton range in 3D coordinates within the difference of a few milimeters compared to the simulated dose distribution.…”