A MULTIMODE DIGITAL-DETECTOR READOUT FOR SOLID-STATE MEDICAL IMAGING DETECTORS

A multipurpose digital detector readout for medical imaging applicatio ns is presented. The readout is capable of measuring both current and charge, allowing a single detector array to perform imaging functions previously accomplished with two separate machines. The circuit employ s a variable rate Sigma Delta analog-to-digital converter (ADC) to mea sure current over a 130-dB dynamic range in a 1 kHz band and resolve c harge pulses down to 360e(-) at 100 000 events/s, Detector currents of up to 7 mu A and charge pulses as large as 25 fC can be measured. A l ow-noise charge sensing amplifier (CSA) is combined with digital pulse shaping to optimize the noise performance and flexibility of the char ge measurements, Fabricated in an 1.2 mu m complimentary metal-oxide-s emiconductor (CMOS), the circuit occupies 1.5 mm(2) and dissipates 11 mW/channel from a 5 V supply.