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The single photon emission computed tomography (SPECT) based on pixelated Cadmium Telluride (CdTe) detectors has
been promising for high resolution small animal imaging. For the feasibility of our CdTe detector (PID350, AJAT,
Finland) in small animal SPECT system, we compared the quality of reconstructed images from our SPECT system to
those from a conventional small animal SPECT system with a NaI(Tl) detector. The CdTe detector had 0.35 mm × 0.35
mm2 pixels, which is similar to the size of the available detector (PID350, AJAT, Finland). The CdTe detector size was
44.8 × 44.8 mm2 and the thickness of this detector was 1 mm. The size of NaI(Tl) detector was 44 mm × 96 mm2 and the
thickness of this detector was 5 mm. The intrinsic spatial resolution of CdTe detector and that of NaI(Tl) detector were
0.35 mm FWHM and 2.3 mm FWHM, respectively. The parallel hole collimator of lead was 25 mm high, and the
septum was 0.2 mm high. The parallel hole collimator was hexagonal with a 0.5 mm radius. The Monte Carlo
simulations were performed to assess both SPECT systems. All projections were obtained using 120 projection views
acquired from 0° to 360° with a 3° step. Slices were reconstructed using an Ordered Subsets Expectation Maximization
(OS-EM) with 5 iterations and 4 subsets. We compared the quality of the images from each system in terms of spatial
resolution (FWHM), and sensitivity. The spatial resolution of system using CdTe and that of system using NaI(Tl)
detector were 2.32 mm FWHM and 3.31mm FWHM, respectively. The system sensitivity for our SPECT with CdTe and
NaI(Tl) detector were 23.22 count/sec/MBq and 54.06 count/sec/MBq, respectively. Our simulation results indicated that
our SPECT with CdTe detector showed better spatial resolution compared to SPECT with NaI(Tl) detector. These results
demonstrate that SPECT imaging using a pixelated CdTe detector can improve the performance of SPECT systems for
small animal imaging in term of spatial resolution.
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