Sinogram-based dynamic imaging using a slow positron camera rotation

The PETRRA positron camera was used for dynamic imaging using a continuous slow camera rotation. There are different approaches to performing dynamic studies on projections directly, most of which are valid for specific assumptions (tracer kinetic model). Our approach is to obtain a time–activity curve (TAC) directly from the sinogram. Assuming that the function representing the activity distribution is separable in time and space, the integral of the spatial part with respect to each bin is constant so that there is a linear relationship between the integral of the projections and the temporal part of the activity distribution function. If there are a few high activity regions distinguishable on the sinogram, a TAC can be obtained for each one. By dividing each projection by the TAC it is possible to obtain a time-independent sinogram and using an analytic or iterative algorithm it is possible to perform image reconstruction. We conclude that this new method might be useful where a blood vessel, heart or tumour is in the field of view.