Objective : Dedicated positron emission tomography (PET) scanners designed for specific organs or clinical applications require compact detector modules with high depth-of-interaction (DOI) and time-of-flight (TOF) capabilities. In this study, we present the design and evaluation of a compact, ready-to-use PET detector panel optimized for such scanners.

Approach : The panel, measuring 98.4 × 104.2 mm² , comprises a 4 × 3 array of four-layer, dual-readout detector towers. Detector towers operate in side-irradiation configuration, thereby enabling DOI measurement across the layers, while axial positioning is derived from the dual-ended readout. Each tower is built from a 8 × 4 × 1 array of 2.05 × 4.4 × 30 mm³ Lutetium Fine Silicate (LFS) crystals, axially coupled to strip-shaped multi-pixel photon counters, with both ends of each strip read out through independent electronic channels. A high-speed electronic readout system based on the picoTDC application-specific integrated circuit was developed to enable precise timing and amplitude measurements. Calibration and performance evaluations were conducted under realistic and scaled conditions. A full-range energy calibration was performed at crystal-level using multiple gamma-emitting isotopes to linearize the detector's response and extract energy resolution. Calibration for axial-positioning along the length of the crystals (between two readout ends) was achieved through a simple flood irradiation-based method, eliminating the need for point-specific irradiations.

Main results : Average energy resolutions of 14.2%, 14.3%, 15.3%, and 15.4% were achieved for crystals in layers 1 through 4, respectively. DOI and transaxially positioning steps of 4.4 mm, and 2.05 mm, respectively are obtainable based on layer and crystal pitch. The measured axial spatial resolutions were 3.78 mm, 3.84 mm, 4.01 mm, and 4.78 mm full-width-half-maximum for layers 1 through 4, respectively. TOF resolution averaged 196 ± 7 ps for layer 1-1 pair, gradually degrading to 220 ± 17 ps for layer 4-4 pairs.

Significance : Balancing performance, scalability, and manufacturability, this detector panel offers a practical and easily calibratable solution for next-generation organ-dedicated PET systems with DOI-TOF capability.