Design of a CZT based breast SPECT system

A high-resolution SPECT instrument dedicated to breast imaging has been designed incorporating arrays of collimated Cadmium-Zinc-Telluride (CZT) detectors tiled on either a cylindrical surface or a hemispherical surface surrounding the breast. The performance characteristics of a three-segment rotating parallel-hole collimator as well as a stationary multiple pin-hole collimator were considered for the cylindrical system. A stationary multiple pin-hole collimated system was also considered for the hemispherical design. Monte Carlo studies suggest that at almost equal spatial resolution of 0.5 cm, the cylindrical design with parallel-hole collimator would have an approximately a factor of two higher geometrical efficiency than the hemispherical pinhole collimated system including effects of attenuation in the breast. However, whereas the parallel-hole collimator must be rotated to acquire data from multiple angles of view, the pin-hole version has the advantage of recording data from 112 views in a stationary mode. Monte Carlo studies of filtered backprojection as well as a Bayesian reconstruction approach including attenuation and scatter within the breast, where the breast was modeled as a 15 cm hemisphere of uniform activity distribution containing three spherical lesions of diameters 1.0 cm, 0.7 cm and 0.5 cm respectively suggest that the 0.5 cm could be detected with either design in a one-hour SPECT study assuming a 10:1 tumor to background ratio. The authors conclude that a high resolution breast SPECT instrument where the resolution is limited to about 0.5 cm is viable with CZT detectors.