Variation of gamma camera photographic image density with count rate

In recent years there has been a gradual shift in gamma camera image recording toward the use of transparency films. When this occurs one encounters the intermittency effect. This effect causes the image density to increase as the count rate increases. In addition, density may also increase because the light output per count from the cathode ray tube also increases as the count rate increases. If these effects are not taken into account, images obtained at low count rates may be too light and those obtained at high count rates may be too dark. This paper discusses these phenomena and presents experimental data that shows how image density varies with respect to count rate for several commonly used films.