High-resolution Positronium Lifetime Imaging of Extended Heterogeneous Biological Samples

• Published in: 2023 IEEE Nuclear Science Symposium, Medical Imaging Conference and International Symposium on Room-Temperature Semiconductor Detectors (NSS MIC RTSD) p. 1
• Main Authors: Huang, B., Wang, Z., Zeng, X., Goldan, A., Qi, J.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 04.11.2023
• Subjects: Biology; Muscles; Positron emission tomography; Positrons; Semiconductor detectors; Spatial resolution; Surface reconstruction
• ISSN: 2577-0829
• DOI: 10.1109/NSSMICRTSD49126.2023.10338475

About 40% of positrons form positroniums in human tissue prior to annihilation. The lifetime of ortho-positroniums (oPs) is sensitive to the tissue microenvironment and can potentially provide valuable information for monitoring disease progression and treatment response. To obtain lifetime images using currently available positron emission tomography (PET) scanners, several statistical image reconstruction methods have been proposed but were only validated by imaging well-separated point sources. In this study, we design an experimental method to perform high-resolution positronium lifetime imaging of an extended heterogenous biological sample. A Na-22 source was employed to irradiate the ex vivo tissue sample with free positrons. The prompt gammas and annihilation photons were detected to reconstruct a positron lifetime image on the tissue surface. The annihilation activity image showed that a significant quantity of positrons annihilated in the tissue of interest after passing through the air, providing positronium lifetime events carrying the lifetime information in the tissue. The reconstructed lifetime image by our previously developed SIMPLE method showed clear separation between the muscle and fat regions with much better spatial resolution and lifetime contrast than those obtained by the direct TOF backprojection method.