Computer Assisted Tomography without a Computer

In computer assisted tomography, measured projections are filtered and back-projected to obtain the reconstructed image. With radioisotopic imaging, however, detected events are processed individually so that it is also possible to both filter and back-project individual events. Since the filter function is the same for each event (except for the location of the function), the filter function can be stored and then back-projected from the proper location for each event. A computer is not necessary, therefore, for either the filtering or back-projection calculations.