The aim is to develop a high resolution, high contrast detector for digital x-ray imaging systems. The target detector would have a Detective Quantum Efficiency much greater than 80%, a limiting resolution of at least 10 lp/mm, ultra-low noise, linear response and a dynamic range of more than 14 bits. The proposal is to build such a detector by using CdZnTe crystals. The detector crystal is hybridized to a readout integrated circuit device that allows the signal to be collected efficiently, digitized and stored in a computer as an image matrix. The planned individual detector unit, designed for use in a slot scan system, has 192 stages in the scan direction and 384 columns in the non-scan direction. The detectors are planned to be mounted in a staggered array with overlap at the ends up to the full breast x-ray image width (approximately 25 cm) in the non-scan direction. The detector pixel pitch will be 50 microns with 100% fill factor. Compared to the present film systems, a reduction of patient dose by a factor of six can be achieved without loss of image quality. To achieve these objectives, in this proposal we plan to develop and demonstrate: a high quality and high spatial resolution bump bonding technique; an optimized readout IC for the CZT crystals; and a reliable, low-cost, high throughput technique to test and select high quality, high uniformity CZT crystals.
