Contrast enhancement of the liver. Evaluation by automated contiguous pixel search

Eight dogs were infused with one of three different contrast agents: meglumine diatrizoate, iosulamide meglumine, or an ethiodized oil emulsion (EOE 13). Image intensity in the liver was evaluated globally and regionally by means of an automated pixel sampling method to determine differences in the rate of enhancement produced by the three agents. The results of the automated method were compared with those of the standard manual cursor method. The automated method showed that liver parenchyma was enhanced uniformly by all three contrast agents. The maximum degree of enhancement (Mean +/- SEM) for the three agents was diatrizoate, 12.0 +/- 3.5 Hounsfield units (HU); iosluamide, 21.3 +/- 3.5 HU; and EOE 13, 37.2 +/- 4.25 HU. With the manual cursor method, contrast enhancement was about 20% more than estimated by the automated method. The automated method is better for evaluating the magnitude and pattern of contrast agent enhancement of the entire liver, since the currently employed cursor technique requires multiple evaluations to evaluate the entire liver.