Multi-pinhole collimator optimization for high resolution SPECT imaging

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 (0.5×0.5 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 ⩽140 keV. Complete 360° 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