Clinical Validation of a New Digital Spectrometer System for Range Verification in Proton Therapy

Particle therapy is a promising technique for cancer treatment because of the characteristic dose deposition of protons in matter. As an alternative method to conventional photon therapy, it allows a precise irradiation of the tumor volume in the patient body, while sparing healthy, radiosensitive organs.
However, body modifications during the treatment period hinder the precise positioning of the Bragg peak in the target volume, and thus limits the accuracy of proton therapy.
These uncertainties and the lack of a suitable monitoring system, which should control the range in vivo and real-time during the irradiation, make it necessary to establish broad safety margins around the irradiated volume in the patient body. This decreases the effectiveness of the therapy and reduces the benefits compared to conventional photon therapy. To counteract this, many solutions for a clinically applicable system for online range verification are under discussion. One approach is the Prompt Gamma Timing (PGT) method. The energy-resolved timing spectra of the detected photons encode the range information of the primary protons and allow a real time range verification [1]. The concept of PGT was developed and tested in first experiments, which confirm that PGT is a promising method for range assessment [2]. Especially the simplicity of the concept according to the experimental implementation justifies a further development with special focus on clinical applications.