Eighty-five patients with single/multiple nodular hepatic lesions (10 focal nodular hyperplasias, 37 liver hemangiomas, 24 metastases and 16 hepatocellular carcinomas; 2 patients had associated lesions) were examined with dynamic single-slice sequences and fast i.v. bolus injection of Gd-DTPA. The dynamic single-slice technique was used to evaluate the peculiar features of the dynamic enhancement. The snapshot sequence proved best to provide the high temporal resolution of the dynamic parenchymal enhancement (scanning time < 1 second, one frame every third second). The following variables were investigated: nodular lesion intensity in the first basal snapshot image, enhancement appearance and its contemporaneity with arterial, venous or portal flows, enhancement gradient relative to surrounding liver parenchyma, morphologic features of the enhancement and its centrifugal/centripetal patterns. The enhancement curve of focal nodular hyperplasia increased very quickly during the first 20-25 seconds. This enhancement was quite similar to the arterial one and always occurred before portal and systemic venous times. Hemangiomas exhibited a typically slow growth-curve in the first 120 seconds, with a positive final gradient value relative to liver parenchyma. The appearance of peripheral contrast enhancement was a typical sign after 30 seconds. Metastases exhibited similar dynamic enhancement to hemangiomas, but peripheral enhancement was never observed and, after 120 seconds, gradient was null or negative relative to the adjacent liver parenchyma. Moreover, enhancement always followed portal times. Hepatocellular carcinomas showed an early growth curve, preceding portal times, but less marked than in hyperplasia. The study of our series provided the preliminary semiology of early dynamic enhancement patterns, which is quite specific to recognize and differentiate nodular hepatic lesions.
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