Reconstruction methods for quantitative brain SPECT

The effects of various reconstruction algorithms and compensation techniques for brain SPECT (single-photon-emission computed tomography) reconstruction are investigated. The conventional FB (filtered backprojection) and iterative ML-EM (maximum-likelihood estimation-maximization) algorithms are used. Projection data were acquired via dual energy windows for use in scatter compensation. Assuming uniform attenuation, the Chang attenuation compensation algorithm is applied. Restoration filters are used with the FB algorithms to compensate for the average effects of collimator and scatter response functions. Two-dimensional (2-D) and three-dimensional (3-D) compensation methods are compared. Compensation for the one-dimensional spatially variant collimator response, using an iterative reconstruction method, is shown. The results show that conventional reconstruction and compensation methods provide substantial improvement in reconstructed image quality and quantitative accuracy compared with no compensation. 3-D processing gives better results than 2-D processing. Iterative reconstruction provided more accurate quantitation with a substantial increase in computational cost