NEW 3D BACKPROJECTION AND FILTERING METHOD FOR PET USING ALL DETECTEDEVENTS

We have developed a new 3D reconstruction method for positron emission tomography (PET) based on the backprojection and filtering (BPF) tech nique. It was developed for a rotating large-area detector PET scanner . By starting with event-by-event backprojection rather than histogram ming into projections, the positional information from the scanner is fully utilized. Also the data are condensed into 3D image format, rath er than 4D format as required by projection based methods. Our new met hod - Atrax - is based on a combination of analytic and algebraic tech niques, eliminating the requirement of a shift-invariant point spread function (PSF). All the detected events are used and there is no restr iction on the field of view. The key to the method is factorization of the deconvolution step into an axial and a transaxial part. A prelimi nary 2D reconstruction is used for the calculation of the axial PSF. T he axial deconvolution is performed with an iterative method, and the transaxial deconvolution is done in Fourier space. Atrax can produce i mages with lower noise than standard BPF due to the incorporation of m ore events, and with improved resolution as compared to projection bas ed methods due to full utilization of the positional information.