Performance evaluation of PETbox: A low cost bench top PET scanner dedicated to high throughput preclinical imaging

Abstract

PETbox is designed to be a low cost and easy to use bench top small animal PET scanner dedicated for high throughput quantitative pharmacokinetic and pharmacodynamic studies. To achieve this goal, the scanner is integrated with a complete animal management system that provides life support including reproducible positioning, temperature control, anesthesia, real-time monitoring of animal respiration and a pathogen barrier. This approach minimizes the overall cost and complexity of preclinical PET imaging and should enable non-imaging scientists to embrace the technology. The system uses two opposing detector heads, each one consisting of a pixilated BGO array coupled to two H8500 multi-channel photomultiplier tubes. The BGO crystals were segmented into 20 × 44 arrays with a pixel pitch of 2.2 mm and a total active area of 44 mm × 96.8 mm. Position and timing signals from the photomultiplier tube readout circuitry were connected to a field programmable gate array (FPGA) board with eight ADC channels, each running at 100MHz. Signal processing algorithms were developed for the FPGA to process received PET events and raw list-mode data were generated by the FPGA board and transferred to a host PC for storage. Basic system performance parameters were measured. The system has an average intrinsic spatial resolution of 1.72mm FWHM along detector long axis and 1.84mm FWHM along detector short axis. The coincidence timing resolution was measured to be 4.1ns FWHM. The average energy resolution of the crystals was 19.8% and the absolute sensitivity of the system was measured to be 3.8% at the center of the gantry. Initial imaging studies were also performed with live mice. A mouse tumor xenograft was imaged 1 hour after a 32uCi [18F]FDG injection for 20 minutes. 3D images were generated using a ML-EM method. Results demonstrate the capability and potential of the PETbox system for dedicated high throughput mouse studies such as biodistribution and organ uptake quantification.