Positron imaging device with plural coincidence channels and graded radiation absorption

The invention is in a positron imaging scintillation camera for detecting the radioactive distribution of positron events within an organ of interest of a living subject utilizing dual scintillation detectors positioned on opposite sides of the organ and registration means for recording positron events. The improvement comprises continuous, uniform graded absorption shielding positioned between each of the detectors and the organ of interest, discrimination means defining at least two separate acceptable ranges of radioactive energy, and coincidence gating means connected to the dual detectors for permitting the registration of only those radioactive events which are detected in coincidence by the dual detectors. (JTA)