Development and Performance Evaluation of a Time-of-Flight Positron Emission Tomography Detector Based on a High-Quantum-Efficiency Multi-Anode Photomultiplier Tube

We present the development and performance evaluation of time-of-flight (TOF) positron emission tomography (PET) detector modules designed for a proof-of-concept prototype of a TOF PET scanner based on the advanced high-quantum-efficiency (high-QE) multi-anode photomultiplier tube (PMT) (Hamamatsu H10966A-100 with super-bialkali photocathode) coupled with LGSO scintillation crystals (3 mm × 3 mm × 20 mm) whose cross section is smaller than that of crystals used in current clinical scanners. Compact dedicated front-end analog electronics combined with the high packing density and large effective area of the multi-anode PMT allow a modular detector design and thus a flexible and extendible geometry of the PET system. We optimized the electrical parameters (trigger threshold level, high voltage of PMTs, and amplifier gain) to yield the best timing resolution and acquired excellent flood map quality, energy resolution, and timing resolution with the optimal setup; the average distance-to-width ratio (DWR) of crystal peaks for 40 detectors was 5.3 ± 1.0, and the average energy resolution and coincidence resolving time (H10966A-100 vs. H10966A-100) were 11.04 ± 0.80% (FWHM) and 341 ± 45 ps (FWHM) respectively. The detector modules developed in this study and optimized their parameters to yield the best detector performance will be useful for the future development of the next generation TOF PET scanners based on them.

I. Introduction

In positron emission tomography (PET) studies, the measurement of the arrival time difference of coincident gamma-ray pairs (time-of-flight (TOF) information) allows more accurate localization of positron emitters on the line-of-response (LOR), leading to improved reconstructed PET image quality [1]–[3]. Propagation of image noise along the LOR during the projection process in image reconstruction is limited within a restricted space (segmented LOR) using the TOF information, enhancing the signal-to-noise ratio (SNR) of PET images [4]. Accordingly, the TOF measurement improves the diagnostic power of PET and/or reduces the scan time or radiation dose [5], [6]. Another benefit of TOF information is the mitigation of image artifacts due to inconsistent or missing data in PET measurements [7], [8]. In addition, the joint estimation of activity and attenuation data can be facilitated by the improved TOF measurement, and is useful in reducing artifacts due to the misalignment of emission and transmission data and ultimately eliminating the necessity of transmission data for PET attenuation correction [9], [10].