New PET Imaging Concept Evaluates Tumor Microenvironment Without New Tracers: Researchers validate the principle of Positronium Ratio Imaging (PRI) using direct three-photon decay detection

Researchers at The University of Tokyo, in collaboration with the University of York, have demonstrated Positronium Ratio Imaging (PRI), a novel imaging technique additional to PET, that detects three-photon decay from positronium. By measuring the ratio of three-photon to two-photon annihilations, this method enables the evaluation of tissue microenvironments, such as hypoxia and intermolecular void, using existing PET radiopharmaceuticals. The study was published in Communications Physics.

Fig.1 Schematics of Three-Photon Imaging developed for Positronium Ratio Imaging (PRI)

Fig.2 Imaging results when mixing ¹⁸F-FDG with water (left) and macroporous material (XAD-4, right).

(a) Conventional PET image (2γ) (b) Three-photon image (3γ) (c) First 3γ/2γ image

Papers

Journal: Communications Physics

Title: Advancing PET through Direct Imaging of Three-Photon Decay using Pure Positron Emitters

Authors: Macoto Fujimoto*, Riku Sato, Moh Hamdan, Mizuki Uenomachi, Peter Caradonna, Laura Stephenson, Archie Montgomery, Julien Bordes, James R. Brown, Daniel P. Watts, Kenji Shimazoe*

DOI: 10.1038/s42005-026-02782-6