The electronics hardware aspects of a prototype experimental SPECT system

Abstract

The paper discusses various features of the electronic hardware for a single photon emission imaging (SPEI) experimental system. The key design requirements and constraints are determined by considering the following: intended application and functional and technological aspects. Specifically, the design needed to deliver high performance mixed signal hardware. The design also needed to satisfy the following additional constraints: high density PCB design, high voltage segregation, high immunity to switching noise originating from isolated DC/DC converters, negligible crosstalk between digital and analogue signals, the need to fit in a confined space, achieve high density detector stacking and provide analogue output signals with low noise. This paper describes the design concepts and specific measures applied to achieve the following: low parasitic capacitance on the sections of the PCB artwork used for detector interfacing, sufficient segregation of circuits at different potentials, adequate suppression of switching noise and isolated high speed digital buses with small skew. For example, the reduction in parasitic capacitance is achieved by controlling both interlayer and fringe capacitances. Further, high stacking density is achieved by careful selection of components by their sizes and 3D planning. The need for mechanical heat-sinks is eliminated by distributing heat dissipation over a number of components and PCB surfaces. The PCB type is selected by comparing benefits and drawbacks of rigid and flex-rigid technologies. Finally, several factors regarding the wire-bonding of the ASIC and the detectors are discussed.