# TOF-PET with high-efficiency TlCl crystals

> **NIH EB R01** · UNIVERSITY OF CALIFORNIA AT DAVIS · 2026 · $610,380

## Abstract

Summary
Time-of-flight positron emission tomography is a very effective nuclear imaging modality for the diagnosis and
staging of a range of pathologies such as cancer, cardiovascular diseases, or musculoskeletal disorders.
Commercial TOF-PET scanners currently employ lutetium-(yttrium)-oxyorthosilicate (L(Y)SO) crystal detectors
coupled to silicon photomultipliers (SiPMs) to achieve coincidence time resolutions (CTR) between 200-500 ps
full width at half maximum (FWHM).
High production costs of L(Y)SO crystals and their intrinsic radiation background are currently hindering the
evolution and spread of very promising TOF-PET modalities such as long axial field-of-view (LA-FOV) scanners
or studies involving very low doses such as cell tracking or imaging with theranostic agents. New scintillator
materials with lower production cost, radiation background-free, and with TOF-level timing accuracy are needed.
We propose to use thallium chloride (TlCl) as a scintillator material for TOF-PET. TlCl is a material with a simple
cubic structure that allows for a relatively easy and flexible doping process. Preliminary data obtained with TlCl
crystals doped with beryllium (Be) and indium (I) show a very fast scintillation component of ~10 ns that has a
high potential for very accurate timing measurements. TlCl has a greater detection efficiency than LYSO or even
bismuth germanate (BGO) for 511 keV gammas, is background radiation-free, and its estimated production cost
is 1/3 of L(Y)SO based on its low melting point of 430C (compared to 2050C for L(Y)SO) and simple lattice
structure. Moreover, unlike BGO, TlCl uniquely combines a very fast scintillation process with a high Cherenkov
generation yield to further boost timing potential.
We aim to prove the feasibility of using TlCl detectors for TOF-PET by combining expertise in crystal growth,
simulation of light generation and detection, and benchtop characterization. First, will study the effects of Be and
I as dopants in TlCl

## Key facts

- **NIH application ID:** 11324303
- **Project number:** 5R01EB034062-04
- **Recipient organization:** UNIVERSITY OF CALIFORNIA AT DAVIS
- **Principal Investigator:** Gerard  Arino Estrada
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** EB
- **Fiscal year:** 2026
- **Award amount:** $610,380
- **Award type:** 5
- **Project period:** 2023-04-01T00:00:00 → 2027-03-31T00:00:00

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11324303

## Citation

> US National Institutes of Health, RePORTER application 11324303, TOF-PET with high-efficiency TlCl crystals (5R01EB034062-04). Retrieved via AI Analytics 2026-05-19 from https://api.ai-analytics.org/grant/nih/11324303. Licensed CC0.

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