Towards real-time ion range verification via hybrid Compton-PET 3D imaging at isochronous cyclotrons
Abstract
Range uncertainties remain a major limitation to the full clinical exploitation of proton therapy, motivating reliable in-vivo range-verification techniques. This work presents an experimental investigation of a hybrid Prompt-Gamma Imaging (PGI)--Positron-Emission Tomography (PET) concept at the isochronous cyclotron of the West German Proton Therapy Centre under clinically representative pencil-beam-scanning conditions. Because this accelerator delivers a quasi-continuous beam, a pulsed shoot-and-step structure was imposed to mimic the interruptions associated with clinical energy-layer switching. This enabled PGI during irradiation and PET and delayed Compton imaging during beam-off intervals within the same sequence. Four two-plane Compton cameras were arranged in a co-planar cross-shaped geometry around the beam isocenter. Polyethylene phantoms were irradiated with 100~MeV protons at known positions along the beam axis. Their positions were estimated from reconstructed one-dimensional profiles using supervised machine-learning models trained exclusively on Monte Carlo simulations. PET achieved the best performance, with a root-mean-square deviation of 0.8~mm, followed by PGI with 1.6~mm. Delayed Compton imaging based on e+ annihilation photons and 10C* decays yielded 2.4~mm and 3.8~mm, respectively. PET retained good performance down to 1% of the original event statistics, whereas PGI became increasingly statistics-limited. These results demonstrate the complementary strengths of hybrid PGI--PET and support its development towards millimetre-scale proton-range verification under clinically relevant irradiation conditions.
Related
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- Emittance preservation under multifaceted CSR effects in isochronous deflection structures for multikiloampere bunches
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BibTeX
@misc{balibreacorrea2026towards,
title = {{Towards real-time ion range verification via hybrid Compton-PET 3D imaging at isochronous cyclotrons}},
author = {Javier Balibrea-Correa and V. Babiano-Suarez and J. Lerendegui-Marco and P. Torres-Sánchez and I. Ladarescu and M. Pallàs and B. Brusasco and J. Wulff and C. Bäumer and A. Tarifeño-Saldivia and C. Domingo-Pardo},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25993},
eprint = {2609.25993},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25993},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Towards real-time ion range verification via hybrid Compton-PET 3D imaging at isochronous cyclotrons
AU - Javier Balibrea-Correa
AU - V. Babiano-Suarez
AU - J. Lerendegui-Marco
AU - P. Torres-Sánchez
AU - I. Ladarescu
AU - M. Pallàs
AU - B. Brusasco
AU - J. Wulff
AU - C. Bäumer
AU - A. Tarifeño-Saldivia
AU - C. Domingo-Pardo
PY - 2026
DA - 2026/09/22
PB - arXiv
DO - 10.48550/arxiv.2609.25993
UR - https://arxiv.org/abs/2609.25993
AB - Range uncertainties remain a major limitation to the full clinical exploitation of proton therapy, motivating reliable in-vivo range-verification techniques. This work presents an experimental investigation of a hybrid Prompt-Gamma Imaging (PGI)--Positron-Emission Tomography (PET) concept at the isochronous cyclotron of the West German Proton Therapy Centre under clinically representative pencil-beam-scanning conditions. Because this accelerator delivers a quasi-continuous beam, a pulsed shoot-and-step structure was imposed to mimic the interruptions associated with clinical energy-layer switching. This enabled PGI during irradiation and PET and delayed Compton imaging during beam-off intervals within the same sequence. Four two-plane Compton cameras were arranged in a co-planar cross-shaped geometry around the beam isocenter. Polyethylene phantoms were irradiated with 100~MeV protons at known positions along the beam axis. Their positions were estimated from reconstructed one-dimensional profiles using supervised machine-learning models trained exclusively on Monte Carlo simulations. PET achieved the best performance, with a root-mean-square deviation of 0.8~mm, followed by PGI with 1.6~mm. Delayed Compton imaging based on e^+ annihilation photons and ^10C^* decays yielded 2.4~mm and 3.8~mm, respectively. PET retained good performance down to 1% of the original event statistics, whereas PGI became increasingly statistics-limited. These results demonstrate the complementary strengths of hybrid PGI--PET and support its development towards millimetre-scale proton-range verification under clinically relevant irradiation conditions.
ER -