High resolution CsI(Tl)/Si-PIN detector development for breast imaging

High resolution multi-element (8×8) imaging arrays with collimators, size matched to discrete CsI(Tl) sdntillator arrays and Si-PIN photodetector arrays (PDA's) were developed as prototypes for larger arrays for breast imaging. Photodetector pixels were each 1.5 × 1.5 mm2 with 0.25 mm gaps. A 16-element quadrant of the detector was evaluated with a segmented CsI(Tl) scintillator array (1.5x1.5x6 mm3 segments with 0.25 mm septa) coupled to the silicon array. The scintillator thickness- of 6 mm corresponds to 85% total gamma efficiency at 140 keV. Pixel energy resolution of < 8% FWHM was obtained for Tc-99m (140 keV). Electronic noise was 41 e" RMS corresponding to a 3% FWHM contribution to the 140 keV photopeak. Detection efficiency uniformity (± o%) measured with a Tc-99m flood source was 4.3% for a ∼ 10% energy 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 conlrasl ([max-iniii]/[max+min]) was 0.94. The energy resolution and spatial characteristics of the new imaging detector exceed those of other scintillator based imaging detectors. A camera based on this technology will allow: 1) Improved Compton scatter rejection; 2) Detector positioning in close proximity to the breast to increase signal to noise; 3) Improved spatial resolution; and 4) Improved efficiency compared to high resolution collimated gamma cameras for the anticipated compressed breast geometries. © 1998 IEEE.

Duke Scholars

Author Martin Paul Tornai Radiology