Room: Stars at Night Ballroom 1
Purpose: Proton therapy is an increasingly popular method of irradiating malignant tumours for various cancer types. While the localization of the dose profile in proton therapy promises an improvement in tumor control probability compared to conventional photon treatments, there are still a number of limitations. Factors such as uncertainty in tissue stopping powers contribute significantly to the total uncertainty in the range of the protons.
Methods: If a small â?¹Â²Mo marker is administered to the tumour region, its response to proton-activation can be used to monitor the irradiation of the tumour. Direct nuclear and fusion-evaporation reactions between the proton beam and marker nucleus result in the emission of prompt and beta-delayed characteristic gamma rays. These beta-delayed gamma rays from the activated target can be detected off-beam for a more precise measurement on a greatly reduced background compared to on-beam. This can be achieved by periodically switching the beam on and off during delivery.In order to determine the viability of this technique and optimize the experimental setup, GEANT4 was used in combination with ROOT to simulate fraction delivery. Shielded HPGe detectors will be used in order to measure the energies of beta-delayed gamma rays with high resolution.
Results: Comparing the simulated intensity of beta-delayed gamma-rays produced from competing reactions on â?¹Â²Mo yields a precise measurement of the range of the proton beam relative to the marker. These results are supported by data obtained from a proof-of-principle experiment at TRIUMF.
Conclusion: â?¹Â²Mo has been shown to be suitable as a marker for range verification in proton therapy. The data obtained through simulation and experiment has been used to justify follow-up experiments at TRIUMF's treatment facility.