الفهرس 
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Abstract
Hypervascular focal lesions of the liver are frequent. Although characterization of hypervascular lesions is difficult, it is a key step in disease management.
Because of its high contrast resolution, MRI, using fast imaging technique, non-specific and liver-specific contrast agents, is a very powerful modality for the detection and characterization of hypervascular focal hepatic lesions.
Even in very complicated cases, an analysis of signal intensity data and dynamic enhancement patterns after intravenous contrast administration and the status of the remainder of the liver allows for an accurate differential diagnosis of hypervascular focal lesions.
If chronic liver disease is present, the differential diagnosis includes mimics, HCC, and NRH.
Mimics—Regenerative nodules, dysplastic nodules and Transient hepatic enhancement difference are the most common lesions that require differentiation from HCC in chronic liver disease. Regenerative nodules are typically isointense relative to the liver with all sequences. Dysplastic nodules may show hypervascularity without washout or a capsule (unlike HCC) and are generally T2 hypointense rather than hyperintense. (THED) is hypervascular, geographically shaped, typically peripheral in location, and occult with all other sequences.
Hepatocellular Carcinoma—In cirrhotic patients, a nodule larger than 1 cm that demonstrates arterial enhancement followed by washout is the most specific sign for HCC.
Nodular Regenerative Hyperplasia—NRH is an uncommon entity that is seen in patients with Budd-Chiari syndrome or hepatic vascular disorders. T2 hypointensity and delayed isoenhancement help differentiate NRH from HCC .Like FNH; NRH will show isoenhancement or hyperenhancement on 1-hour to 3-hour delayed images obtained with Gd-BOPTA.
If the liver is normal, the most common causes of hypervascular liver lesions are hemangioma, FNH, adenoma, peripheral cholangiocarcinoma and hypervascular metastases.
Hemangioma— Typical features includes lobulated contours, high signal intensity on T2-weighted images, low signal intensity on T1-weighted images, and peripheral nodular enhancement with progressive fill-in.
Focal Nodular Hyperplasia— Typical findings includes lesion homogeneity, lobulated contours, fibrous septa and central bright T2 scar, iso-intensity on T1 and T2-weighted images, global, intense and transient enhancement during the arterial phase, and delayed enhancement of fibrous components. FNH will typically show iso- or hyper-enhancement on delayed images obtained 1–3 hours after Gd-BOPTA administration.
Adenoma— Heterogeneous lesion displaying variable-T1& hyper T2 signal with presence of fat, blood, and heterogeneous hypervascularity are helpful distinguishing features. Adenomas are hypointense on 1-hour to 3-hour delayed images obtained with Gd-BOPTA.
Peripheral Cholangiocarcinoma— Is generally isointense on T1-weighted images, with variable hyperintensity on T2 weighted images with minimal or moderate rim enhancement in the arterial phase with progressive & concentric filling with contrast material in the later phases. In-drawing of the liver capsule is useful distinguishing feature.
Hypervascular Metastases— The T1 and T2 relaxation times of liver metastases vary considerably, usually appear more hyperintense than the normal liver and more hypointense than cyst and hemangioma on T2-weighted image .Hypervascular metastases will show hypo-enhancement on 1-hour to 3-hour delayed images obtained with Gd-BOPTA.