The dynamic magnetic resonance study of focal liver lesions by FLASH sequences with bolus intravenous gadolinium-DTPA]

Thirty-five patients with hepatic hemangioma (n = 12), metastasis (n = 10), hepatocellular carcinoma (HCC) (n = 10) and focal nodular hyperplasia (n = 3) were examined with the fast low-angle shot (FLASH) technique and an intravenous bolus injection of Gd-DTPA. In order to differentiate the lesions, the following criteria were used: a) pre Gd-DTPA intensity of lesions; b) post Gd-DTPA patterns of contrast enhancement. On the basis of these criteria, an unquestionable differential diagnosis could be made. Hemangiomas were characterized by an hypointense mass before Gd-DTPA, by peripheral contrast enhancement and by subsequent continuous hyperintense fill-in; thus, hemangiomas were visualized as hyperintense lesion during the late phase. Before contrast administration hypovascular metastases appeared as hypointense; they were characterized by delayed uptake of contrast agent. HCCs were hyperintense lesions before contrast administrations; then, quick contrast enhancement and rapid decrease in signal intensity were observed with visualization of a hyperintense ring due to the capsule. Finally, focal nodular hyperplasia appeared isointense or hypointense relative to normal liver on precontrast scans; the lesions were enhanced transiently with subsequent quick dismission of contrast agent. This initial experience suggests dynamic contrast-enhanced MR imaging as an effective method to improve the differential diagnosis among hepatic tumors when precontrast T2-weighted images are equivocal.