Dose‐volume delivery guided proton therapy using beam on‐line PET system

TLDR

Proton therapy concentrates dose on a tumor using a scanned or modulated Bragg peak, and the irradiated volume can be verified by detecting positron‑annihilation gamma rays from proton‑induced nuclear reactions with PET imaging. The study aims to accurately evaluate the proton‑irradiated volume. A beam‑on‑line PET system (BOLPs) with a high‑resolution planar detector was used to measure activity distribution immediately after proton irradiation of a gelatinous water phantom and a rabbit, enabling dose‑volume delivery guided proton therapy. The activity‑distribution range tracked changes in the physical range, and image differences under altered beam conditions clearly delineated the irradiated volume.

Abstract

Proton therapy is one form of radiotherapy in which the irradiation can be concentrated on a tumor using a scanned or modulated Bragg peak. Therefore, it is very important to evaluate the proton‐irradiated volume accurately. The proton‐irradiated volume can be confirmed by detection of pair annihilation gamma rays from positron emitter nuclei generated by the target nuclear fragment reaction of irradiated proton nuclei and nuclei in the irradiation target using a positron emission tomography (PET) apparatus, and dose‐volume delivery guided proton therapy (DGPT) can thereby be achieved using PET images. In the proton treatment room, a beam ON‐LINE PET system (BOLPs) was constructed so that a PET apparatus of the planar‐type with a high spatial resolution of about was mounted with the field of view covering the isocenter of the beam irradiation system. The position and intensity of activity were measured using the BOLPs immediately after the proton irradiation of a gelatinous water target containing nuclei at different proton irradiation energy levels. The change of the activity‐distribution range against the change of the physical range was observed within . The experiments of proton irradiation to a rabbit and the imaging of the activity were performed. In addition, the proton beam energy used to irradiate the rabbit was changed. When the beam condition was changed, the difference between the two images acquired from the measurement of the BOLPs was confirmed to clearly identify the proton‐irradiated volume.