Sensitivity and Spatial Resolution Optimization of a High-Resolution Preclinical PET With a Unique Acquisition Method

Abstract

EasyPET.3D is a preclinical positron emission tomography (PET) scanner using a unique scanning method based on two face-to-face detector modules with two axes of motion. The sensitivity and spatial resolution were optimized for mouse imaging by studying the operating parameters related to motor motion (speed and step angle), following the NEMA NU 4-2008 Standards. Moreover, the impact of the energy window and positron range on the images was assessed. The fan motor should operate at a speed of 20 full steps/s, while the fan ( ${F}=0.014^{\circ }$ –0.113°) and axial ( ${A}=0.9^{\circ }$ –9.0°) step angles are chosen depending on the study’s purpose. The image quality experiment demonstrated the high-resolution capability of easyPET.3D. A 200–750 keV energy window maximized the sensitivity (+200%) without significantly increasing scatter fraction (SF) (+35%). In contrast, the acquisition protocol made it difficult to conclude about the positron range effect. The feature with the most impact on the scanner’s performance is the fan motor speed. A lower fan motor speed of 20 steps/s enhanced sensitivity and spatial resolution by +122% and +60%, respectively, increased noise equivalent count rate by 155%, decreased SF by 7%, and improved recovery coefficient by +35%.