Dynamic imaging and tracer kinetic modeling for emission tomography using rotating detectors

When performing dynamic studies using emission tomography the tracer distri bution changes during acquisition of a single set of projections. This is p articularly true for some positron emission tomography (PET) systems which, like single photon emission computed tomography (SPECT), acquire data over a limited angle at any time, with full projections obtained by rotation of the detectors. In this paper, an approach is proposed for processing data from these systems, applicable to either PET or SPECT. A method of interpolation, based on overlapped parabolas, is used to obtain an estimate of the total counts in each pixel of the projections for each required frame-interval, which is the total time to acquire a single comple te set of projections necessary for reconstruction. The resultant projectio ns are reconstructed using traditional filtered backprojection (FBP) and tr acer kinetic parameters are estimated using a method which relies on counts integrated over the frame-interval rather than instantaneous values. Simul ated data were used to illustrate the technique's capabilities with noise l evels typical of those encountered in either PET or SPECT, Dynamic datasets were constructed, based on kinetic parameters for fluoro-deoxy-glucose (FD G) and use of either a full ring detector or rotating detector acquisition. For the rotating detector, use of the interpolation scheme provided recons tructed dynamic images with reduced artefacts compared to unprocessed data or use of linear interpolation, Estimates for the metabolic rate of glucose had similar bias to those obtained from a full ring detector.