STRATEGIES TO IMPROVE 3D WHOLE-BODY PET IMAGE-RECONSTRUCTION

An algorithm is described for three-dimensional whole-body (3DWB) imag e reconstruction in positron emission tomography. For whole-body appli cations, improvements to the popular fixed-axial-acceptance-angle tech nique are achieved by combining axially adjacent projection data avail able with a long-axis data set. Time-consuming reprojection of unmeasu red oblique lines of response is reduced or eliminated by axial overla p of bed positions, while pixel variance and reconstructed axial resol ution are made more uniform by the overlap. Improvements in noise and resolution uniformity are accompanied by gains in reconstruction effic iency, and may be optimized against increased acquisition time due to overlapping acquisition segments and reduced axial coverage. An 11-det ector-ring overlap improves axial uniformity in coronal images of a lo ng, uniform cylinder from 23% to 8% with uniform axial resolution. Ass ociated with a 37% improvement in reconstruction time is a 34% reducti on in axial coverage for four bed positions. A smaller degree of overl ap is found to provide the best trade-off between image uniformity, to tal scan duration, and reconstruction time because of a proportionally greater reduction in reprojected lines of response. Using a sample op timization scheme, we find a three-ring overlap is best for a 60 cm ax ial field of view and a five-ring overlap for an 80 cm axial field of view.