EXACT AND APPROXIMATE REBINNING ALGORITHMS FOR 3-D PET DATA

This paper presents two new rebinning algorithms for the reconstructio n of three-dimensional (3-D) positron emission tomography (PET) data, A rebinning algorithm is one that first sorts the 3-D data into an ord inary two-dimensional (2-D) data set containing one sinogram for each transaxial slice to be reconstructed; the 3-D image is then recovered by applying to each slice a 2-D reconstruction method such as filtered -backprojection, This approach allows a significant speedup of 3-D rec onstruction, which is particularly useful for applications involving d ynamic acquisitions or whole-body imaging, The first new algorithm is obtained by discretizing an exact analytical inversion formula, The se cond algorithm, called the Fourier rebinning algorithm (FORE), is appr oximate but allows an efficient implementation based on taking 2-D Fou rier transforms of the data, This second algorithm was implemented and applied to data acquired with the new generation of PET systems and a lso to simulated data for a scanner with an 18 degrees axial aperture, The reconstructed images were compared to those obtained with the 3-D reprojection algorithm (3DRP) which is the standard ''exact'' 3-D fil tered-backprojection method, Results demonstrate that FORE provides a reliable alternative to 3DRP, while at the same time achieving an orde r of magnitude reduction in processing time.