Feasibility study of using two 3-D position sensitive CZT detectors for small animal PET

An experimental small animal PET using two 3-D position sensitive CdZnTe detectors was developed and tested. Each 1.5×1.5×1 cm³ CdZnTe detector employs 11 by 11 pixellated anodes wire-bonded to the VAS3.1/TAT3/MCR3 readout electronics. Each detector can obtain the deposited energy and 3-D coordinates for single-pixel and multiple-pixel events. Both systems achieved energy resolutions of better than 1.0% FWHM at 662 ReV for single-pixel events and better than 1.5% FWHM at 662 ReV for two-pixel events. The position resolution of each detector was estimated to be ∼1.3×1.3×0.5 mm³. Modifications to the firmware of the readout board and additions of custom-built circuitry enabled coincidence measurement between two 3-D CdZnTe detector systems using VAS3.1/TAT3/MCR3 readout systems. Spatial resolution improvements by using depth of interaction (DOI) and by identifying the first interaction using Compton scattering angle reconstruction are reported and discussed.