RT Journal Article SR Electronic T1 Progress of a MRI compatible small animal PET scanner using dual-ended readout detectors JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 527 OP 527 VO 60 IS supplement 1 A1 Zhonghua Kuang A1 Xiaohui Wang A1 Ning Ren A1 San Wu A1 Mengxi Zhang A1 Juan Gao A1 Ziru Sang A1 Zhanli Hu A1 Junwei Du A1 Yongfeng Yang YR 2019 UL http://jnm.snmjournals.org/content/60/supplement_1/527.abstract AB 527Objectives: Dual-modality small animal PET/MRI imaging is a very powerful tool in biomedical research since PET and MRI are highly complementary. For a small animal PET scanner, high spatial resolution is required to clearly visualize the radiotracer distribution and to improve the quantification of the tracer by reducing the partial volume effect. High sensitivity is also required to improve quantification of the tracer by increasing the signal-to-noise ratio of image or to reduce the scan time and injection dose. Depth of interaction (DOI) effect is the biggest limitation for a small animal PET scanner to simultaneously achieve high sensitivity and uniform high spatial resolution. In this work, depth encoding detectors by using dual-ended readout of pixelated LYSO arrays with SiPM arrays are used to develop a MRI compatible small animal PET insert with high spatial resolution, high sensitivity and long axial field of view. Materials and Methods: The scanner consists of 4 detector rings with 12 detector modules per ring. The detector ring diameter of the scanner is 111 mm and the axial field of view is 106 mm. The scanner gantry is cooled by an Air-Jet Crystal Cooler to ensure a stable operating temperature. MRI shielding consisting of carbon tube and copper foil is used. The LYSO arrays have 23×23 crystals of 1.0×1.0×20 mm3. The outer dimension of the LYSO array is 24.6×24.6×20 mm3. The LYSO arrays are read out by two 8×8 Hamamatsu SiPM arrays placed at the opposite ends. The size of each SiPM pixel is 3×3 mm2 and the gap between pixels is 0.2 mm. The active area of the SiPM array is 25.4×25.4 mm2. The 64 pixels of a SiPM array are read out with a resistive network circuit to reduce the number of signals from 64 to 4. The signal processing electronics consists of 12 singles processing units (SPU) with each processing 32 channel signals, a coincidence processing unit (CPU), a system clock and synchronizing board and power supply boards. The initial performance of the scanner was measured by using a Na-22 point source placed at the center axial field of view with different radial offsets. The images are reconstructed by using the maximum-likelihood expectation-maximization (MLEM) algorithm. The MRI compatibility of one PET detector module was also measured. Results: All crystals can be clearly resolved from the flood histogram and the detectors achieve a DOI resolution of 1.96 mm and an energy resolution of 18.9%. A sensitivity of 15.1% was achieved at center of the scanner for an energy window of 250-750 keV. A uniform spatial resolution of ~0.8 mm was obtained for the center 50 mm of the field of view. The MRI has negligible effect on the performance of PET detector and PET detector has small effect on the signal-to-noise ratio of MRI image. Conclusions: A MRI compatible small animal PET insert consisting of 48 depth encoding detectors by using dual-ended readout was developed. The initial performance of the scanner was obtained. In the future, the NEMA performance of the scanner will be measured and phantom and animal studies will be performed. Acknowledgments: This work is supported by the National Natural Science Foundation of China (Grant No. 81527804) and the Basic Research Program of Shenzhen (Grant No. JCYJ20160608153434110, JCYJ20170818161940079).Corresponding author: Yongfeng Yang, yf.yang@siat.ac.cn