Design and initial performance of PETbox4, a high sensitivity preclinical imaging tomograph

PETBox4, currently under development at the Crump Institute is a new tomograph dedicated to preclinical imaging of mice. This system presents a significant improvement on sensitivity and spatial resolution compared to the first generation PETBox. We report here on its design and initial performance characteristics. Methods: PETBox4 consists of four opposing detector panels arranged in a box like geometry. Each panel is made by a 24 × 50 array of 1.825 × 1.825 × 7mm BGO scintillation crystals with a crystal pitch of 1.9025mm. Each scintillator array is coupled to two Hamamatsu H8500 photomultiplier tubes via a glass light guide. Images for a 45 × 45 × 94mm FOV are reconstructed with the ML-EM algorithm and a system model based in a parameterized detector response. The complete system is integrated with a real time respiratory monitoring system, and provides anatomical reference images via a combination of x-ray projection, optical images and a digital mouse atlas. Results: The measured crystal energy resolution ranged from 13.9% to 40.4% FWHM, with a mean of 18.0%. With an energy window of 150 650 keV optimized for mouse imaging, the peak absolute sensitivity was approximately 14% at the center of FOV based on the results of GATE Monte Carlo simulations. The intrinsic detector spatial resolution was 1.5mm FWHM in both transverse and axial directions. The reconstructed image spatial resolution for different positions in the FOV ranged from 1.32mm to 1.93mm, with an average of 1.46mm. Initial imaging studies were performed with tillable phantoms and live mice. Conclusion: In comparison to the first generation two panel PETBox system, PETBox4 achieves substantial improvements on sensitivity and spatial resolution, while it provides full 3D tomographic PET images, retaining the small overall footprint and provides a novel anatomical reference approach.