A 1.5 mm BGO PET detector with DOI measurement

Abstract Objective. This study aims to develop and validate a depth-of-interaction (DOI) positron emission tomography (PET) detector based on a bismuth germanate (BGO) crystal array for high-sensitivity small-animal PET imaging, and to investigate the feasibility of using a light-sharing window (LSW) structure for DOI encoding in BGO detectors despite their inherently low light yield. Approach. A 10 × 8 BGO array with individual crystal dimensions of 1.5 × 1.5 × 20 mm 3 was coupled to a multi-pixel photon counter array using a 2 × 2 crystal-to-sensor configuration. A 6 mm air-gap LSW was introduced between adjacent crystal pixels to generate DOI-dependent light sharing. DOI performance was evaluated using a mechanical collimation experiment, and a vertical line-source irradiation method combined with histogram matching was further implemented to generate Ratio-to-DOI lookup tables from a single static acquisition. Main results. The proposed detector achieved an intrinsic DOI resolution of 4.4 mm full width at half maximum (FWHM), a mean absolute error of 2.2 mm, and an average energy resolution of 17.4% at 511 keV. Using the vertical line-source irradiation calibration method, a DOI resolution of 4.9 mm FWHM was obtained in a single measurement, demonstrating comparable performance to the mechanical collimation calibration with substantially reduced calibration complexity. Significance. These results demonstrate the feasibility of applying the LSW method to low-light-yield BGO detectors and provide a practical, cost-effective DOI solution for high-sensitivity small-animal PET imaging.