Sensitivity, Resolution, and Linearity of the Scintillation Camera

Radioisotope cameras are relatively new instruments for imaging the distribution of γ-ray or positron-emitting isotopes in vivo. They produce pictures similar to those made by medical radioisotope scanners, showing the uptake of tracer compounds in tumors and organs. Cameras can produce pictures in much less time than scanners because of their higher sensitivity and their ability to view all parts of the subject continuously. In the scintillation camera described here, an array of 19 multiplier phototubes view a single, large, thin, sodium iodide crystal. From the relative amount of light seen by each phototube when a scintillation is produced, the position is determined in two dimensions and it is displayed as a point flash of light on an oscilloscope. Pictures are obtained by taking a time exposure of the oscilloscope screen. Pinhole or parallel multichannel collimation is used with γ-ray emitters, and coincidence techniques are used with positron emitters.