Data acquisition for a medical imaging MWPC detector

Abstract

Multiwire proportional chambers, combined with drilled Pb converter stacks, are used as position sensitive gamma-ray detectors for medical imaging at Queen's University. This paper describes novel features of the address readout and data acquisition system. To obtain the interaction position, induced charges from wires in each cathode plane are combined using a three-level encoding scheme into 16 channels for amplification and discrimination, and then decoded within 150 ns using a lookup table in a 64 Kbyte EPROM. A custom interface card in an AT-class personal computer provides handshaking, rate buffering, and diagnostic capabilities for the detector data. Real-time software controls the data transfer and provides extensive monitor and control functions. The data are then transferred through an Ethernet link to a workstation for subsequent image analysis.