The jPET-D4: imaging performance of the 4-layer depth-of-interaction PET scanner

The jPET-D4 is a high-performance brain PET scanner which achieves not only high spatial resolution but also high scanner sensitivity by discriminating 4-layer depth-of-interaction (DOI) information. The scanner is designed to have 5 rings of 24 detector blocks each, and the detector block consists of 1,024 GSO crystals of 2.9 mm × 2.9 mm × 7.5 mm, which are arranged in 4 layers of 16 × 16 arrays. In this paper, we investigated the imaging performance of the jPET-D4 prototype where one of the 5 block-detector rings was assembled. In order to reduce computational cost while retaining the advantage of DOI information in iterative image reconstruction, we have proposed the DOI compression (DOIC) method which reduces data dimensions with suppressing resolution loss. We have also proposed an approximated system model for the jPET-D4 which enables fast system matrix calculation while preserving image quality. The experimental results show that almost uniform spatial resolution of 2-3 mm is obtained over the field-of-view by using the 4-layer DOI information. A Huffman phantom image clearly shows the excellent imaging performance of the jPET-D4.