NaI gamma camera performance for high energies: Effects of crystal thickness, photomultiplier tube geometry and light guide thickness

• DOI: 10.1002/mp.17043
• Publication Date: 2024-04-03T18:05:52Z
• Authors: Valerio Cosmi; Beien Wang; Marlies C. Goorden; Freek J. Beekman
• Keywords: Gamma camera; Silicon Photomultiplier; Positron emission

Abstract Background Gamma camera imaging, including single photon emission computed tomography (SPECT), is crucial for research, diagnostics, and radionuclide therapy. cameras are predominantly based on arrays of multipliers tubes (PMTs) that read out NaI(Tl) scintillation crystals. In this way, standard gamma can localize ɣ‐rays with energies typically ranging from 30 to 360 keV. the last decade, there has been an increasing interest towards imaging outside conventional clinical energy range, example, theragnostic applications preclinical multi‐isotope positron (PET) PET‐SPECT. However, equipped 9.5 mm thick crystals which result in limited sensitivity these higher energies. Purpose Here we investigate what extent thicker scintillators improve photopeak isotopes while attempting maintain spatial resolution. Methods Using Monte Carlo simulations, analyzed multiple PMT‐based configurations detectors monolithic NaI (Tl) 20 40 thickness. Optimized light guide thickness together 2‐inch round, 3‐inch 60 × 2 square, 76 square PMTs were tested. For each setup, assessed sensitivity, resolution, spatial, depth‐of‐interaction (DoI) resolution (140 keV) high (511 ɣ using a maximum‐likelihood algorithm. These metrics compared those “standard” mm‐thick crystal detector round PMTs. Results Estimated sensitivities 511 keV 27% 53% scintillators, respectively, 2.2 4.4 times than most cases, benefits instead ones, regardless their size. Lateral DoI best smaller (2‐inch square) outperform more cost‐effective larger PMT setups (3‐inch square), layout shape have negligible (< 10%) effect Best was obtained PMTs; 140 keV, lateral 3.5 irrespective scintillator thickness, improving 2.8 2.9 crystals, respectively. PMTs, resolutions 4.5 3.9 3.7 indicating moderate performance degradation by Additionally, 7.0 5.6 12.1 5.9 obtained. Conclusion Depending size shape, use substantially at energies, slightly improved or mildly degraded