Dedicated single-photon-emission computed tomography
(SPECT) systems based on pixelated semiconductors such as cadmium telluride
(CdTe) are in development to study small animal models of human disease. In
an effort to develop a high-resolution, low-dose system for small animal
imaging, we compared a CdTe-based SPECT system and a conventional
NaI(Tl)-based SPECT system in terms of spatial resolution, sensitivity,
contrast, and contrast-to-noise ratio (CNR). In addition, we investigated
the radiation absorbed dose and calculated a figure of merit (FOM) for both
SPECT systems. Using the conventional NaI(Tl)-based SPECT system, we
achieved a spatial resolution of 1.66 mm at a 30 mm source-to-collimator
distance, and a resolution of 2.4-mm hot-rods. Using the newly-developed
CdTe-based SPECT system, we achieved a spatial resolution of 1.32 mm FWHM at
a 30 mm source-to-collimator distance, and a resolution of 1.7-mm hot-rods.
The sensitivities at a 30 mm source-to-collimator distance were 115.73 counts/sec/MBq and 83.38 counts/sec/MBq for the CdTe-based SPECT and
conventional NaI(Tl)-based SPECT systems, respectively. To compare
quantitative measurements in the mouse brain, we calculated the CNR for
images from both systems. The CNR from the CdTe-based SPECT system was 4.41,
while that from the conventional NaI(Tl)-based SPECT system was 3.11 when
the injected striatal dose was 160 Bq/voxel. The CNR increased as a function
of injected dose in both systems. The FOM of the CdTe-based SPECT system was
superior to that of the conventional NaI(Tl)-based SPECT system, and the
highest FOM was achieved with the CdTe-based SPECT at a dose of 40 Bq/voxel
injected into the striatum. Thus, a CdTe-based SPECT system showed
significant improvement in performance compared with a conventional system
in terms of spatial resolution, sensitivity, and CNR, while reducing the
radiation dose to the small animal subject. Herein, we discuss the
feasibility of a CdTe-based SPECT system for high-resolution, low-dose small
animal imaging.