1. A method of processing patient data using a radiation detector and a computer, said method comprising the steps of: using said radiation detector to acquire image data representing an image, said acquiring performed for some period of time using the radiation detector; using the computer for automatically detecting and isolating a feature portion of the image; identifying at least one region of interest of the image based on said feature portion; generating an activity versus time array corresponding to the at least one region of interest from said image data; and analyzing the activity versus time array for generating an output for use by a user.