Choice of contrast material for four-hour delayed contrast-enhanced computed tomography of the liver

Four-hour delayed contrast-enhanced computed tomography (DCECT) shows promise for improved detection of focal liver lesions. No previous studies have examined the use of nonionic contrast materials for DCECT. The authors undertook a case-controlled study in monkeys to define the relative efficacies of iopamidol and diatrizoate for DCECT. In this model, diatrizoate made the liver significantly more opaque at four hours than did iopamidol (mean 126.5 vs 87.6 HU, P less than or equal to 0.05). Opacification of the gallbladder and biliary tract occurred more often and was denser with diatrizoate. The relative efficacies of biliary excretion correlate with similarities in molecular structure. While it has been shown that the increased density from DCECT with diatrizoate may allow detection of more metastatic lesions, the clinical utility of the inferior parenchymal density obtained with iopamidol, extrapolated to be approximately 11 to 14 HU in humans, remains to be-established.