Lag in radiographic imaging systems: simple methods for evaluation.

Abstract

Lag is an important measure of performance in radiographic imaging systems that are used for dynamic studies. This paper describes some simple, noninvasive techniques that can be used to evaluate lag under clinical conditions. The image receptor is exposed through a copper plate perforated with regularly spaced holes or slits and rotating at a known angular velocity. The resulting image can be evaluated visually to determine the point at which separate holes appear to blur. Alternatively, a light-sensitive diode connected to an oscilloscope can be used to determine the decay rate of the signal from an individual slit. A correlation between these two techniques has been obtained that enables lag to be estimated from a visual assessment of the image of the rotating plate.