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Conventional partial orbit SPECT acquisition (90/spl deg/, 120/spl deg/ or 180/spl deg/ depending on number of camera heads) on multihead cameras enhance the problems caused by patient motion or change in organ position ("cardiac creep"), since the misplaced data are present at several intervals in the projection set. The authors investigated the effects of source motion and developed new image motion correction methods based on 360/spl deg/ acquisition of each detector on a three camera SPECT system. Experimental measurements with point sources and cardiac phantom were used to evaluate the influence of source motion on SPECT images. A point source phantom was rotated 5-30/spl deg/ CCW and moved axially 0.5-4.0 cm. A cardiac phantom was moved in laterally (0.5-4.0 cm) and in the axial direction (0.5-4.0 cm). Cross-correlation of images from different heads at the same angular position is used to detect and correct for motion. Two correction methods were investigated: (1) summation of complete 360/spl deg/ projection sets without correction, (2) time normalization of projection frames without motion to replace frames affected by motion. The first method corrects for small displacement of the source (

Recent studies show Tl-201 and Tc-99m MIBI to have high sensitivity for detecting and differentiating tumor from benign lesions in the breast. A study was conducted to optimize the design of a multi-pinhole collimator for high spatial resolution SPECT imaging of the breast to detect small tumors (0.5/spl times/0.5 cm). High sensitivity is achieved by using multiple pinholes, and rotating the camera 90-180 degrees around the breast. Monte Carlo simulation studies and analytical methods are applied to determine the number of holes, hole position, hole aperture size, conical field of view, and focal length of the collimator to optimize spatial resolution and sensitivity for breast imaging. Shielding is optimized to accommodate an energy range of 50-511 keV. An image reconstruction algorithm for cone beam imaging geometry for rotating single pinhole SPECT will be modified to accommodate simultaneous imaging from multiple pinholes with limited angular sampling. Special emphasis is placed on evaluation of imaging with small pinhole apertures (1-2 mm diameter), that are required to achieve the resolution of 3-7 mm at the distance of 10-15 cm with radionuclides having energies /spl les/140 keV. Complete 360/spl deg/ acquisition of the breast tumor model was simulated to study the artifacts in reconstructed images due to limited angle acquisition and to select an optimal reconstruction algorithm.