Abstract: In a diagnostic apparatus of this invention, an accumulated or deposited state of an administered radioactive medicine in an organ or the like of a living body is detected from the outside of the living body by detecting portions, each constituted by at least one scintillation detector and at least one collimator, so as to obtain an image of the state. The apparatus includes three detecting portions. Driving mechanisms are provided for at least two of the detecting portions to linearly move and rotate them.

Abstract: Gamma rays radiated from a radioisotope injected into a subject under examination are detected by a scintillation camera, and position signals indicative of the detected position of the gamma rays and an energy signal are applied to a data-processing unit for imaging the distribution of the radioisotope within the subject. A pulse height analyzer analyzes an energy discrimination signal and provides an imaging control signal when the pulse height of the energy discrimination signal falls within a window of interest. The data-processing unit is responsive to the application of the imaging control signal to thereby image the distribution of radioisotopes within the subject on the basis of the position signals and the energy signal. The energy discrimination signal may have a pileup waveform in which at least two peaks are produced substantially at the same time due to simultaneous detection of gamma rays.