Ultra high resolution pinhole SPECT for small animal study

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-7200 A 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 2]. The data were collected at 4 degree increments over 360 degrees. The Feldkamp method was used for image reconstruction. Before the image reconstruction, the authors corrected the COR of the pinhole collimator. The imaging voxel was 0.27×0.27×0.27 mm³ [case 1] or 0.4×0.4×0.4 mm³ [case 2]. From the experiments with a resolution phantom the spatial resolution (FWHM) was 1.1 mm [case 1] or 1.3 mm [case 2]. 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. The authors also investigated the spatial resolution of the reconstructed image by means of simulations