A Novel Precise Proton Range Diagnostic for Proton Therapy Treatment Unlike conventional x-ray radiotherapy that uses x-ray photons to propagate through the tissue and kill tumor cells, proton therapy is an advanced treatment that uses high-energy protons. While x-ray photons deposit their energy in a continuous fashion along their travel in tissue, energetic protons deposit most of their energy at the location where they stop (i.e., tumor cells), minimizing the damage on surrounding healthy tissues. Accurate targeting of the proton beam into the tumor is therefore crucial to assure the success of the treatment and minimize side effects. The approach disclosed herein incorporates real-time diagnostic techniques into existing processes to monitor the end point of the proton beam while the beam is scanning. This allows the operator of the proton accelerator to adjust the proton beam so that it precisely targets the desired region of tissue. No.: M-916 Inventor(s): Dale M Meade Kenneth W Hill Lan Gao Manfred L Bitter Philip C Efthimion