الفهرس 
Anatomy of the liverOnly 14 pages are availabe for public view
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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 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.
Summary and Conclusion
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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.
Summary and Conclusion
113
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