Results from a Further Scaled up Prototype of a 1-millimeter Resolution Clinical PET System

We have been developing a 1-millimeter resolution clinical positron emission tomography (PET) system dedicated to loco-regional (e.g. breast, head/neck, etc.) cancer imaging. Due to a dual-panel, patient-adjustable geometry and position-sensitive, pixelated scintillation detector design, the system enables high sensitivity in order to realize 1 mm reconstructed resolution. The basic detector unit comprises two position-sensitive avalanche photodiodes (PSAPD), each coupled to an array of 8 × 8 lutetium-yttrium oxyorthosilicate (LYSO) crystals which we refer to as a dual-LYSO-PSAPD module, and each panel consists of such 512 detector modules. Recently, we scaled up the system to increase a field-of-view (FOV) by 25%, and in this work, we characterize the scaled-up prototype system. Energy spectrum and coincidence time spectra are presented, and the 511 keV positron annihilation photopeak energy resolution and coincidence time resolution were measured to be 11.0 % and 25.6 ns, respectively. Lastly, we imaged an ²² Na rod source, with 1.6 mm diameter, and the resulting reconstructed images are shown. Full-width-half-maximum (FWHM) values of line profiles on X-Z, X-Y, and Y-Z plane were 0.86 mm, 0.94 mm, and 1.25 mm, respectively.