Near 65ps-fwhm in 20mm-LSO TOF-PET by using a time walk correction based on multi-photon stamps: a Monte Carlo study

TL;DR

This Monte Carlo study demonstrates that using multi-photon time stamps and DOI-dependent corrections significantly improves TOF resolution in LSO-based PET detectors, achieving near 65 ps FWHM.

Contribution

The paper introduces a novel method to estimate photon time walk from multi-photon detection sequences and combines it with DOI correction to enhance TOF resolution.

Findings

TOF resolution improved from 99.7 ps to 66.4 ps with correction

Strong linear DOI dependence of light sharing observed

Photon time walk can be estimated from photon detection series

Abstract

Aim: Investigate whether a time walk assessment derived from crystal light sharing and multi-photon time stamps can improved the TOF resolution. Method: Monte Carlo simulations were performed for SiPM (FBK-NUV-HD) coupled to conventional 4x4 mm2 pixelated LSO (0.2%Ca:Ce ) and also coupled to 8x4 mm2 pixelated LSO in which a triangular optical window allows light sharing between the two 4x4 mm2 sub-pixels depending on the DOI. A time walk estimation was modelled as a DOI dependent weighted sum of the time differences within the photons detection sequence. The DOI dependent weights were optimized in order to get the best TOF resolution. Results: A strong linear DOI dependence of the light sharing between the two 4x4 mm2 sub-pixels was observed. The TOF resolutions for a 4x4x20 mm3 LSO were 99.7, 81.2, 66.4 ps-fwhm without any correction, with DOI correction and with DOI dependent time walk correction, respectively. The time walk correction was derived from the 7 time stamps of the (2**k )th photons in the sequence, with k within[0,6]. Conclusion: photon time walk can be estimated from the photon time detection series and can be advantageously combined with the DOI assessment to improve TOF resolution.