Metallic nanoparticles as proton beam range monitor

In clinical practice, dose delivery in proton therapy treatment is affected by uncertainties on the range of the beam within the patient, requiring medical physicists to introduce safety margins on the penetration depth of the beam. Although this ensures an irradiation of the entire clinical target volume with the prescribed dose, these safety margins also lead to nearby healthy tissues exposition and subsequent risk of side effects. Therefore, non-invasive techniques enabling margin reduction through on-line monitoring of prompt gammas emitted along the proton tracks in the patient are currently under development. This study reports on the proof-of-concept to use metal-based nanoparticles, injected into tumour, as a prompt gamma enhancer, helping in the beam range verification. It identifies the limitations of this application suggesting a low feasibility in a realistic clinical scenario but opens some avenues for improvement.