Beam-width-corrected DOI resolution measurement of dual-ended readout PET detectors

Abstract Objective. Dual-ended readout PET detectors provide depth-of-interaction (DOI) information for reducing parallax errors in high-resolution PET imaging. This study compared LYSO detectors with different inter-crystal reflectors and investigated the effect of irradiation beam width on DOI resolution measurements under electronic collimation. Approach. Two 28 × 28 LYSO arrays with 0.75 × 0.75 × 10 mm³ crystals and BaSO₄ or E60 reflectors were characterized in terms of flood-map quality, energy resolution, and DOI resolution. Part of E60 detector (8×8 crystals) was further measured using three irradiation geometries with beam widths of 0.80 mm, 0.62 mm, and 0.46 mm. A beam-width correction was applied to the measured DOI resolution, and the effects of energy selection and empirical flood-map-based inter-crystal scattering (ICS) filtering were evaluated. Main results. The BaSO₄ detector showed better flood-map quality and energy resolution, whereas the E60 detector showed better DOI resolution. In the 400–650 keV energy window, the measured average DOI resolutions of entire 28 × 28 LYSO pixels with irradiation beam width of 1.00 mm were 1.92 and 1.75 mm for the BaSO₄ and E60 detectors, respectively. For the selected 8 × 8 crystal region of the E60 detector, the corrected DOI resolution by subtracting the irradiation beam width improved from 1.19 mm for all events to 1.01 mm after energy selection, and further to 0.86 mm after additional empirical flood-map-based ICS filtering. Significance. Irradiation beam width introduces a geometry-dependent contribution to DOI resolution measurements. Beam-width correction enables more consistent DOI characterization under different irradiation geometries