Development of stationary dedicated cardiac SPECT with multi-pinhole collimators on a clinical scanner

The existing SPECT system for nuclear cardiac imaging suffered from low sensitivity or high cost. In this study we implemented a novel design of the stationary dedicated cardiac SPECT combined with multi-pinhole collimators based on the clinical dual-head scanner with low cost. Previous simulation study has demonstrated the feasibility of the design. Accurate geometry calibration was implemented for image reconstruction. The projection of a 2-mm-diameter sphere source, which was mounted on patient bed and moved through three certain gridding scanning orbits, was acquired for calibration. The geometrical parameters were estimated by fitting the experimental projection centroids to the geometrical model. The reconstruction adopted MLEM algorithm with GPU parallelization based on CUDA. Considering the impact of large pinhole size on image reconstruction, two analytical pinhole models (sampling pinhole model and dual-section Gaussian model) were proposed to derive the system matrix on the fly during reconstruction. The sphere source projection of one view was reconstructed with the two analytical pinhole models and delta model. The reconstruction results of different views' projection were compared. Furthermore, the myocardium phantom study in comparison with parallel-hole SPECT has been performed to evaluate the system. With geometrical calibration, the reasonable reconstruction images were achieved with 10.6 × 12.9 × 9.6 mm
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spatial resolution (FWHM). Analytical pinhole models improved the spatial resolution to 6.8 × 8.0 × 7.2 mm
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and suppressed the deformation while dual-section Gaussian model were slightly better than sampling pinhole model. There was no significant difference between the reconstruction images with one view's and three views' projection, which indicated the stationary imaging property of the SPECT system. Myocardium phantom study demonstrated the superior performance and better defect identification of our proposed SPECT than parallel-hole SPECT. In conclusion, our initial results showed the reasonable images could be achieved on the proposed stationary multi-pinhole dedicated cardiac SPECT. In the future work, more phantom and in vivo experiments would be implemented to evaluate the dedicated cardiac SPECT system.