[ROC (receiver operating characteristic) study for the recognition of liver lesions on the computer tomogram]

ROC examination was based on patient computer tomograms, in which lesions of the liver were simulated by image manipulation. The window width for optimal recognition of the lesions was found to be 128 Hounsfield units (HU). Evaluation of Receiver Operating Characteristics (ROC) by diameters and contrasts of the lesions yielded a contrast detail diagram largely reflecting conditions in clinical practice. The detectability--measured via the smallest visible diameter of the lesions--is inferior by the factor 3 to 60 to the results obtained with hole pattern phantoms. For example, in computer tomograms lesions of the liver of 24 mm and 4 HU or also 11 mm and 10 HU yield 70% true positive and 10% false positive findings.