Imaging Studies from a Large Volume High Resolution Cadmium Zinc Telluride Preclinical PET System

This work presents the initial imaging studies for a large volume CZT preclinical PET system. Two full heads of the final four-headed box-shaped system have been constructed with each head composed of 24 CZT crystals; each crystal is of size 40 × 40 × 5 mm3 with sets of orthogonal anode and cathode electrode strips deposited on opposite sides of the crystals. Crystals are paired to form modules with an anode-cathode-cathode-anode configuration. Each CZT crystal has 39 anode strips and 38 electrodes. Anode strips are 100 µm wide with a 1 mm pitch, and steering electrode are 400 µm wide. The cathode side of the detector module is composed of 8 strips which are 4.9 mm wide with a pitch of 5 mm. Photons enter the crystal in an “edge-on” orientation and pass through the 5×40 mm2 edge, which results in a detection efficiency equivalent to that of 2 cm of LSO scintillator. The readout of the cathode and anode strips are supported by custom front end electronics designed around a readout ASIC. This configuration has 3,456 readout channels with an effective 1,872 anode channels and 384 cathode channels. In this work, we imaged a multi-well multi-isotope phantom composed of various activities of FDG and Co-55 ranging from 50 to 100 µCi. The CNR of a 100 µCi FDG well against background was measured to 33.48.