The aim of the study is to develop an ultra high-resolution pinhole SPECT system and analyze the performance by simulations. The pinhole SPECT was conducted with a Toshiba GCA-7200A gamma camera. The diameter of the pinhole was 1 mm. Data were acquired with a 128×128 matrix, and the distance from the center of rotation (COR) to the pinhole was 20 mm [case 1] or 28 mm [case 2J. The data were collected at 4 degree increments over 360 degrees. The Feldkamp method was used for image reconstruction. Before the image reconstruction, we corrected the COR of the pinhole collimator. The imaging voxel was 0.27×0.27×0.27 mm3 [case 1] or 0.4×0.4×.4 mm3 [case 2J. From the experiments with a resolution phantom the spatial resolution (FWHM) was 1.1 mm [case 1] or 1.3 mm [case 2J. The pinhole SPECT was also examined for in vivo imaging for studies of the heart in mice which were injected with Tc-99m-Tetrofosmin intravenously. In the reconstructed image the heart muscle of the mouse was clearly visualized. We also investigated the spatial resolution of the reconstructed image by means of simulations.
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