An Application-Specific Integrated Circuit for Positron Emission Tomography

Abstract

Improving the performance of positron-emission tomography (PET) systems for small animal imaging requires the use of high-speed detectors, such as a Lutetium Oxyorthosilicate (LSO) crystal coupled to avalanche photodiodes (APDs). We have developed an application-specific integrated circuit (ASIC) for reading out the multiple channels of an LSO-APD detector module for use in a small animal PET system.In this work, we characterize the performance of the ASIC, referred to as the AE172 chip. The AE172 can accommodate both positive and negative input signals, with a programmable conversion gain that ranges from 2.8 mV/fC to 21 mV/fC. The ASIC channels exhibit a linear response and an equivalent noise charge (ENC) of ~2000 electrons, RMS. The timing jitter depends on the amplitude of the input signal; and is less than 1 ns for test signals greater than 100,000 electrons.Connecting the ASIC to a linear APD detector reduces the relative readout noise to 26 electrons referenced to the input of the APD, which is operated at a gain of ~200. An LSO-APD-ASIC detector achieves an energy resolution of 13% for the 511 keV annihilation photons from a 22 Na source, and a coincident timing resolution of ~13 ns.

APD imaging probe for tritium surface contamination

“…To support the simultaneous readout of the 16-channel APD array, an application specific integrated circuit (ASIC) that was developed for APD use was utilized [13]. Each ASIC chip contained 16 channels of preamplifiers, shaping amplifiers as well as the peak tracking circuitry necessary to interface with a computer.…”

Design of a High-Resolution PET Detector Using Avalanche Photodiodes

“…The disadvantage of this design is the relatively large number of readout channels required. In particular, the channel count is a concern if one is using a 16-channel front-end ASIC, as in [9], or if one is using discrete electronics, as in [2].…”