Performance characteristics of a new modular camera based on pixelated crystal for high-resolution pinhole SPECT with comparison to a standard camera with continuous crystal

The purpose of the study is to investigate the performance characteristics of a pinhole SPECT system based on a newly developed modular camera with a pixelated NaI(Tl) crystal with 1.2 mm pixels and 1.4 mm pitch and a 5" R3292 PSPMT. The characteristics are compared to that based on a standard GE AC/T 400 camera with continuous crystal using the same set of tungsten apertures with pinhole diameters of 1.0,1.5 and 2.0 mm. The system spatial resolution and sensitivity were characterized as a function of source-to-pinhole distance and pinhole diameter from the measurements of point spread function (PSF) using ∼150μm ^99mTc point sources. A microSPECT phantom was used to access the system resolution in SPECT imaging and a ^99mTc-MDP mouse bone SPECT imaging from the modular camera based system was demonstrated. The projection data from the phantom and mouse studies were reconstructed using a 3D OSEM pinhole reconstruction algorithm with geometrical misalignment correction. In general, the modular camera based microSPECT system shows slightly poorer spatial resolution as compared to the GE 400 AC/T camera based system using the same set of pinhole apertures. The phantom study indicates that using the same pinhole aperture of 1 mm the modular camera based system can clearly resolve 1.6 mm rods while the GE 400 AC/T camera based system can well resolve 1.2 mm rods. Reconstructed mouse images demonstrate that high image quality can be obtained with the modular camera based pinhole SPECT system despite its slightly poorer system resolution as compared to that based on a standard camera. In conclusion, the modular camera fitted with a shorter pinhole collimator can achieve high-resolution for high quality small animal imaging. With continuous improvements in detector technology, system design and image reconstruction method, modular camera can be an important component of a high-resolution small animal SPECT imaging system.