A Statistical Method of Defining Low Contrast Detectability

Abstract

Low contrast detectability (LCD) refers to the ability of the CT scanner to image small objects which are of very low contrast. Typically the objects are several millimeters in diameter and a few Hounsfield units different from the background material. Low contrast detectability in CT images is often determined by scanning a test phantom with low contrast objects and presenting the resulting images to several observers. This method of determining low contrast detectability is dependent on many variables and results in significant uncertainties in the specified low contrast detectability. In order to provide a more predictable and verifiable measure of low contrast detectability, a statistical method of defining low contrast detectability is given here. Using this method, a statistical measure of low contrast detectability is given for the GE LightSpeed Plus CT scanner. This is also the method used for the statistical LCD quoted in the LightSpeed Plus data sheet.