HIGH-RESOLUTION CSI(TL) SI-PIN DETECTOR DEVELOPMENT FOR BREAST IMAGING/

High resolution multi-element (8x8) imaging arrays with collimators, s ize matched to discrete CsI(TI) scintillator arrays and Si-PIN photode tector arrays (PDA's) were developed as prototypes for larger arrays f ar breast imaging. Photodetector pixels were each 1.5 x 1.5 mm(2) with 0.25 mm gaps. A 16-element quadrant of the detector was evaluated wit h a segmented CsI(TI) scintillator array (1.5x1.5x6 mm(3) segments wit h 0.25 mm septa) coupled to the silicon array. The scintillator thickn ess of 6 mm corresponds to > 85% total gamma efficiency at 140 keV. Pi xel energy resolution of < 8% FWHM was obtained for Tc-99m (140 keV). Electronic noise was 41 e(-) RMS corresponding to a 3% FWHM contributi on to the 140 keV photopeak Detection efficiency uniformity (+/- sigma %) measured with a Tc-99m flood source was 4.3% for a similar to 10% e nergy photopeak window. Spatial resolution was 1.53 mm FWHM and pitch was 1.75 mm as measured from the Co-57 (122 keV) line spread function. Signal to background was 34 and contrast ([max-min]/[max+min]) was 0. 94. The energy resolution and spatial characteristics of the new imagi ng detector exceed those of other scintillator based imaging detectors . A camera based on this technology will allow: 1) Improved Compton sc atter rejection; 2) Detector positioning in close proximity to the bre ast to increase signal to noise; 3) Improved spatial resolution; and 4 ) Improved efficiency compared to high resolution collimated gamma cam eras for the anticipated compressed breast geometries.