Contrast materials for cross-sectional imaging of the abdomen.

Abstract

The development and clinical studies of contrast agents for cross-sectional abdominal imaging presently focus on the diagnosis of liver diseases and suitable oral contrast agents for MR imaging. The well-known paramagnetic agent, gadopentetate dimeglumine is now used for improving the differential diagnosis of liver lesions such as focal nodular hyperplasia in dynamic MR studies. Preclinical studies and initial clinical trials indicate that the new paramagnetic hepatobiliary contrast agent, manganese dipyridoxal diphosphate, might improve the sensitivity of MR imaging in the detection of liver lesions. With respect to dynamic contrast-enhanced CT in the detection of liver lesions, interest has focused on the question of the optimal scanning technique. Promising results have been obtained in initial studies of contrast agents for sonography, called microbubbles. This substance produces good visualization of the vascular status of liver tumors. Nuclear medicine somatostatin receptor imaging may be of special clinical interest because it allows even very small somatostatin-positive metastases to be detected and thus provides specific information for therapy planning in patients with positive scan results. Initial studies have shown that using contrast enhancement with MR imaging of the pancreas improves the contrast between pancreatic tissue and lesions. Manganese dipyridoxal diphosphate is taken up by pancreatic tissue, though the exact mechanism remains to be clarified, and may therefore have potential as a future MR contrast agent for evaluation of the pancreas. A number of oral MR contrast agents have now been tested in larger clinical trials. Both positive and negative oral agents are safe and well tolerated and achieve the aim of reliably delineating the gastrointestinal tract from other organs and pathologies in the abdomen.