An evaluation of the image-intensifier scintillation camera with some comparisons to the single crystal camera.

Abstract

The newly developed Ter-Pogossian image-intensifier scintillation camera (11) (Picker Magnacamera)3 and the widely used Anger single crystal camera4 (1) represent two qualitatively different systems for imaging radioactive events in man. This report presents an objective evaluation of the Magnacamera, with comparisons of the major parameters of these two cameras in static and dynamic scanning situations. General Description of the Ter-Pogossian and Anger Cameras The Magnacamera system consists of a collimated special image-intensifier tube, an Orthicon television tube, and data-recording systems as shown in Figure 1. Radioactive events occurring in the input crystal of the intensifier are amplified in intensity and presented as a small brighter image on the output phosphor as in the conventional radiographic image-amplifier. The output phosphor is optically coupled to the Orthicon where the image is converted into an electronic television signal for “live” display on a TV monitor and on an oscilloscope, from either of which it can be recorded photographically. Moreover, the image can be simultaneously stored on a Videotape recorder at the rate of 60 television frames per second. This allows selective replay through the TV monitor and a variable persistence or standard oscilloscope. Cinescintigraphs can be obtained from either the television monitor or the oscilloscope. Two audio channels on the videotape allow simultaneous or subsequent recording of audio information. Two multichannel collimators are available for the Magnacamera; each is of parallel-hole design and two inches thick. The “coarse” collimator has 700 holes, each about 1/4 inch in width, with septal thickness of 0.006 inch. The “fine” or higher resolution collimator has 2,611 holes, each about 1/8 inch in width, with septal thickness of 0.003 inch. The “fine” collimator has a lower efficiency and requires approximately four times the input activity of the “coarse” collimator to achieve the same picture brightness. The Pho/Gamma system contains a collimated 11-inch diameter, ½ inch thick sodium iodide scintillation crystal optically coupled to a hexagonal arrangement of 19 photomultiplier tubes. Areas within the crystal are “viewed” by the photomultiplier tubes; a scintillation event in any one area is divided proportionally among the 19 photomultiplier tubes, then summed for the X, Y coordinates by an analogue computer which determines its position. The pulse corresponding to this scintillation is reproduced on an oscilloscope in the same relative position that it occupied in the crystal. A pulse-height analyzer is available to filter the pulses and select the energy range to be displayed on the oscilloscope.