Simulation and one-ring prototyping of 1 mm-rod-resolution hemispherical brain PET with TOF-DOI detectors

<i>Objective.</i>Brain positron emission tomography (PET) imaging plays crucial roles in research and diagnosis of various brain diseases. To achieve high spatial resolution and high sensitivity, we proposed a hemispherical geometry which offers higher sensitivity with fewer detectors than a conventional cylindrical geometry. Our developed hemispherical brain PET system, Vrain, has indeed achieved a rod resolution of 2.2 mm with a 229 ps time-of-flight (TOF) resolution. To further improve the spatial resolution, we will use TOF and depth-of-interaction (DOI) detectors with our original crosshair light-sharing (CLS) configuration. This study aimed at estimating the performance of the hemispherical brain PET with TOF-DOI detectors and at developing a one-ring PET prototype with 1.6 mm scintillator pitch CLS-based TOF-DOI detectors.<i>Approach.</i>The sensitivity, rod resolution, and image quality of the TOF-DOI hemispherical brain PET (TDHBP-sim) and Vrain (Vrain-sim) were estimated using Geant4 simulation. A one-ring prototype with a 30 cm diameter was developed using the CLS-based TOF-DOI detectors. The energy resolution, TOF timing resolution, rod resolution, and the Hoffman brain phantom image quality of the prototype were evaluated.<i>Main results.</i>In the simulation study, TDHBP-sim achieved 1.4 times better sensitivity than Vrain-sim. TDHBP-sim visualized 1.0 mm rods and gyri and sulci structures in the brain phantom. In the one-ring experiment, the energy resolution was 11.6% at 511 keV, the TOF timing resolution was 294.6 ps, and 1.0 mm rods were resolved at the central 10 cm-diameter field-of-view. The 0.8 mm-thick radioactivity distribution could be identified in the Hoffman phantom.<i>Significance.</i>The study findings suggested that a hemispherical brain PET with 1.6 mm scintillator pitch TOF-DOI detectors should offer excellent performance including 1 mm rod resolution.