Cherenkov light for total-body Positron Emission Tomography

Project Information

CherPET

Grant agreement ID: 101113474

DOI

10.3030/101113474

Project closed

EC signature date 7 March 2023

Start date 1 October 2023

End date 31 March 2025

Funded under

• European Research Council (ERC)

Total cost

No data

EU contribution

€ 150 000,00

Coordinated by

INSTITUT JOZEF STEFAN
Slovenia

Periodic Reporting for period 1 - CherPET (Cherenkov light for total-body Positron Emission Tomography)

Reporting period: 2023-10-01 to 2025-03-31

Summary of the context and overall objectives of the project

Modern medicine is increasingly oriented toward early diagnosis and personalized treatment, particularly in oncology, where timely and precise imaging is critical. Positron Emission Tomography (PET) plays a central role in this domain, yet current PET systems are expensive, complex, and limited in sensitivity and specificity. These constraints hinder widespread adoption and reduce effectiveness in detecting early-stage disease. While total-body PET systems offer significantly better performance, their cost—driven largely by the extensive use of scintillator material—remains a major barrier. In parallel, advancements in Time-of-Flight (TOF) PET have shown promise in enhancing image quality and signal-to-noise ratios without substantially increasing system cost.

The CherPET project seeks to transform this landscape by developing a new class of affordable, modular PET scanners based on Cherenkov radiation detection rather than conventional scintillation. The core technological innovation centers on the use of lead fluoride (PbF2) crystals as Cherenkov radiators—an inexpensive, easily manufactured alternative to standard materials (scintillating crystals). The system integrates Large Area Picosecond Photon Detectors (LAPPDs) and FastIC ASICs—co-developed with CERN and the University of Barcelona—to achieve sub-100 ps timing resolution, a key performance metric for TOF-PET.

As a proof of concept, CherPET is constructing two flat-panel detector modules, breaking away from the traditional ring geometry and enabling flexible system configurations. The target Coincidence Time Resolution (CTR) is approximately 120 ps FWHM, sufficient to allow for sparse coverage without compromising image quality. Feasibility has been demonstrated through extensive simulations and laboratory measurements.

By merging cutting-edge detector physics with practical, scalable engineering, CherPET aims to deliver high-performance PET imaging systems that are significantly more accessible and affordable, with the potential to reshape clinical practice and expand global diagnostic capacity.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The CherPET project developed a novel PET scanner concept based on Cherenkov photon detection using PbF2 crystals. Detailed Monte Carlo simulations (Geant4/GATE, CASToR) explored optimal detector configurations, surface treatments, and readout geometries (1-, 2-, and 6-sided). These were benchmarked against commercial PET systems like the Siemens Biograph Vision, showing competitive performance in terms of timing, NECR, and image quality.

Novel microchannel-based LAPPD Gen-II light sensors were characterized using laser setups and custom capacitive readout electronics, achieving timing resolutions for single photons as good as 27 ps and spatial resolutions around 1 mm. Integration with PETsys TOFPET2 read-out system allowed full coverage of the LAPPD area with up to 1024 channels. Parallel efforts involved studies of reading out LAPPDs with 64-channel FastIC ASICs, as well as studies of alternative fast solid-state sensors (SiPMs) with efficient single-photon detection.

Prototype bench-top modules using PbF2 and SiPMs or LAPPDs were built and tested. Simulated PET scans with standard NEMA phantoms validated high image quality, even under high scatter conditions thanks to the TOF sensitivity boost. The project also profited from synergy with the main ERC AdG project FAIME in their studies of alternative light sensors for the Belle II upgrade.

Major achievements include demonstrating the feasibility of Cherenkov-based TOF-PET with CTR values in the 120–210 ps range (depending on the crystal and sensor configuration), modular flat-panel detectors, and simulation-verified image quality matching or exceeding clinical standards. The design offers significant cost advantages by using PbF2 and avoiding full-ring geometries. With hardware, software, and electronics in place, and beam tests planned, CherPET is well-positioned to move toward the next stage in prototyping and preparation of clinical prototypes.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The CherPET project advances PET imaging beyond the current state of the art by introducing a fundamentally new detection approach based on Cherenkov radiation in PbF2 crystals, replacing conventional scintillators. This paradigm shift enables high-quality imaging with a very limited energy resolution, relying instead on excellent timing and photon detection efficiency. Simulations of a full PET scanner system confirmed Coincidence Time Resolutions (CTR) of 120–210 ps with SiPMs—better than top commercial systems. A modular flat-panel architecture was validated, allowing flexible and scalable detector configurations. In experimental studies, a sub-30 ps timing in single-photon detection with LAPPDs was confirmed.

Despite the simplified detector design, full-system simulations demonstrated image quality comparable to or better than conventional PET systems, even under challenging conditions with high scatter fractions. Further innovations in advanced reconstruction methods, such as the custom-developed and event-by-event-based TOF kernel in the CASToR reconstruction software, are expected to address the specific timing characteristics, the timing tails typical of Cherenkov-based annihilation gamma detection. The project also investigated custom-developed, high-density readout electronics (FastIC), and achieved a full LAPPD coverage with over 1000 readout channels using PETsys systems.

The potential impact is considerable. Clinically, CherPET could enable mobile and cost-effective PET solutions for underserved regions, small hospitals, and intensive care units, improving early cancer and neurological disease diagnosis. Economically, it offers a considerable reduction in scanner cost and could position Europe as a leader in next-generation PET. Scientifically, it opens new directions in physics-driven imaging, including advanced detector technologies.

To support further uptake, key needs include experimental validation of full-scale modules, optimization of optical coupling and noise control, and strategic IP protection. Commercial pathways—via licensing or spin-outs—will be developed alongside regulatory alignment with NEMA and engagement with EMA/FDA. Access to EU and private financing will be critical for scaling to clinical-grade prototypes and international deployment. With sustained support, CherPET could redefine the future of PET imaging by making high-performance diagnostics broadly accessible and economically viable.

Total-body pannel-based TOF-PET scanner

Two-panel brain scanner