High-precision compton imaging of 4.4 MeV prompt gamma-ray toward an on-line monitor for proton therapy

S. Mochizuki*, J. Kataoka, A. Koide, K. Fujieda, T. Maruhashi, T. Kurihara, K. Sueoka, L. Tagawa, M. Yoneyama, T. Inaniwa

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

15 Citations (Scopus)


Proton therapy is a widely used and effective treatment for cancer. A high-dose concentration of proton beam reduces damage to normal tissues. However, it also requires a high accuracy of irradiation. PET is generally used to verify the proton range after irradiation, but, the distributions of positrons and the energy deposited by protons are not similar to each other. Recently, prompt gamma-ray imaging has attracted attention as a new, online imaging technique. In particular, 4.4 MeV gamma rays emitted from 12C* is one of the best probes to monitor the proton dose, however imaging techniques are far from established. We have developed a novel, 3-D position sensitive Compton camera based on Ce:GAGG scintillators coupled with multi-pixel photon counter (MPPC) arrays, thus making it optimized for imaging in the 1–10 MeV range. The angular resolution is 5 degrees (FWHM) at 4.4 MeV. We have established various methods to discriminate multiple-Compton and escape events, both of which can be critical backgrounds for precise imaging of prompt gamma rays. By irradiating a 70 MeV proton beam on the PMMA phantom, we demonstrated that 4.4 MeV gamma ray image is sharply concentrated on the Bragg peak, as was expected from the PHITS simulation.

Original languageEnglish
Pages (from-to)43-45
Number of pages3
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Publication statusPublished - 2019 Aug 21


  • Compton camera
  • MPPC
  • Prompt gamma-ray imaging
  • Proton therapy

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Instrumentation


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