Prompt gamma imaging with a slit camera for real-time range control in proton therapy: Experimental validation up to 230 MeV with HICAM and development of a new prototype

Treatments delivered by proton therapy are affected by uncertainties on the range of the beam within the patient. To reduce these margins and deliver safer treatments, different projects are currently investigating real-time range control by imaging prompt gammas emitted along the proton tracks in the patient. This study reports on the development and test of a prompt gamma camera using a slit collimator to obtain a 1-dimensional projection of the beam path on a scintillator detector. A first prototype slit camera using the HICAM gamma detector, originally developed for low-energy gamma-ray imaging in nuclear medicine and modified for this purpose, was tested successfully up to 230 MeV beam energy. Results now confirm the potential of this concept for real-time range monitoring with millimeter accuracy in pencil beam scanning mode for the whole range of clinical energies. With the experience gained, a new prototype is under study for clinical beam currents. In this work, we present both the profiles obtained at 230 MeV using HICAM and the description of the new gamma camera prototype design.