Progress in developing focal-plane-multiplexer readout for large CdZnTe arrays for nuclear medicine applications

We report on the construction and initial testing of a 48 x 48 CdZnTe array with 125 mu m pixel spacing and multiplexer readout. Large portions of the array function well but there was a loss of pixels near one corner of the array due to non-interconnecting indium bumps. This problem is readily correctable. Excellent single-pixel spectra were obtained with a (TC)-T-99m source using an adjustment technique that accounts for energy deposited in neighboring pixels. A point-spread function (PSF) taken at 140 keV yielded a spatial resolution of 230 mu m, much better than required for nuclear medicine applications. No problems were found that are not readily correctable or of much less significance for CdZnTe arrays having larger pixel spacing. We are now constructing 64 x 64 CdZnTe arrays with 380 mu m pixel spacing for use in an ultra-high resolution brain SPECT imaging system.