144 channel measurement IC for CZT sensors with energy and time resolution

A 144 channel measurement IC for CZT detectors, used for PET, is presented. Each channel consists of a charge sensitive amplifier, a fast and a slow signal shaper, a peak sampler for the energy acquisition and an event detector based on a time to digital converter to generate an accurate time stamp for each event. The channels are multiplexed to a fast pipeline ADC on demand. Measurement results for the ASIC showed a noise equivalent input charge of 800 e-rms and a time resolution of 737 ps rms. Evaluation results with a CZT detector yielded an energy resolution of 4.4% FWHM at 662 keV with a 137Cs radiation source. The IC is implemented on a 180nm CMOS process with a total chip size of 100 mm2. Preliminary ASIC results with a CZT detector are presented. An energy resolution of 4.4% FWHM at 662 keV was obtained with a 137Cs uncollimated point source, which improved up to 3.5% when the interaction depth was considered.