Custom CMOS integrated circuit for PET tomograph front-end applications

A custom CMOS integrated circuit has been designed, prototyped, and evaluated for PET tomograph front-end applications. The integrated circuit reduces the size, cost, and power consumption of existing PET front-end circuits by over a factor of two. The integrated circuit, fabricated in a standard digital, 2 μ, double-metal, double-poly, n-well CMOS process, has a die size of 6.6 mm × 6.4 mm and power consumption of under 600 mW. The PET front-end CMOS integrated circuit processes energy, position, and timing information from a BGO block detector containing four photomultiplier tubes. Photomultiplier preamplifiers and variable gain amplifiers are connected to summing circuits and gated integrators to provide energy and position (x and y) signals. A constant-fraction discriminator, requiring no external delay line, provides a timing output derived from the sum of the four photomultiplier signals. Eight 7- and 8-bit digital-to-analog converters, connected to a read/write serial data interface, provide gain-control and threshold levels. The measured position, energy, and timing performance (3.05 ns FWHM) of the integrated circuit is comparable to existing discrete PET front-end circuits.