High-resolution SPECT with a CdZnTe detector array and a scintillation camera

The emerging significance of transgenic animal research has motivated the development of radionuclide imaging systems for mice and other small animals. In this work we compare the performance of a scintillation camera with a pinhole collimator (aperture diameter = 0.5 mm, magnification = 8-10) to that of a pixellated CdZnTe hybrid detector array with a parallel-hole collimator (pixel pitch = 0.380 mm, collimator aspect ratio = 27:1, collimator efficiency = 5×10^-5) for SPECT. A "mouse heart" phantom (annular cavity filled with aqueous pertechnetate simulating myocardial perfusion, OD = 5.1 mm, ID = 1.6 mm) and a miniature Carlson grid phantom (3.2 mm cold squares, 4.8 mm pitch) were imaged. Both systems produced high quality images in which objects smaller than two millimeters were resolved. The pinhole system's cone-beam geometry offers advantages, such as an easily variable field of view, and disadvantages such as increased distortion and a decreased field of view close to the pinhole. The semiconductor detector and parallel-hole collimator provide excellent spatial resolution close to the collimator with a fixed field of view of 25 × 25 mm. We believe that both systems will find applications in small animal imaging.