target organ this facilitates technician identification of the target organ and also facilitates repeatability of e g myocardial perfusion studies which require that two studies be performed on a single patient at two different times application_number US 18345194 A description although the invention will be described below in connection with a prospective spect study of a patient 39 s heart it will be understood that this is merely an exemplary application the invention can be adapted to other applications by persons skilled in the art initially and as is shown in fig1 a cardiac spect study is conducted upon a patient 2 in such a study a radioisotope is administered to the patient 2 and the heart 4 of the patient 2 is imaged using a scintillation camera generally indicated by reference numeral 6 a number of frames of planar images collected by the camera 6 is routed to a computer 8 and the planar image itself may be displayed upon a display 10 initially the patient is placed in position and the technician displays on display 10 a persistence image of the patient 39 s heart to confirm that the positioning is proper or to detect mispositioning and to correct it in a conventional study the technician will usually look for particular anatomical landmarks such as the boundary of the patient 39 s heart however if a focussing collimator such as collimator 11 shown attached to the detector of the camera 6 is used the persistence images of these.