DOI:10.2214/AJR.05.0030
AJR 2006; 186:1587-1596
© American Roentgen Ray Society
Focal Nodular Hyperplasia: Lesion Evaluation Using 16-MDCT and 3D CT Angiography
Ihab R. Kamel,
Eleni Liapi and
Elliot K. Fishman
Russell H. Morgan Department of Radiology, Johns Hopkins School of
Medicine, 601 N Caroline St., Suite 3235A, Baltimore, MD 21287.
Received January 7, 2005;
accepted after revision March 23, 2005.
Address correspondence to I. R. Kamel
(ikamel{at}jhmi.edu).
Abstract
OBJECTIVE. The purpose of this article is to present the imaging
features of focal nodular hyperplasia (FNH) using MDCT and 3D CT
angiography.
CONCLUSION. MDCT with advanced image processing is a powerful tool
that may be utilized to identify the imaging features of FNH. These include
the presence of large feeding arteries and draining veins, pseudocapsule,
central scar, and septations. These features can help in the differentiation
of this benign lesion from other hypervascular lesions without the need for
additional imaging, biopsy, or surgery.
Keywords: CT • CT angiography • focal nodular hyperplasia • liver • MDCT
Introduction
Focal nodular hyperplasia (FNH) is a common benign neoplasm of the liver
and is reported in 3-5% of the general population. It is usually discovered
incidentally in young women. The association between FNH and other benign
vascular neoplasms, including cavernous hemangioma
[1], hepatic adenoma, hepatic
adenomatosis, and Budd-Chiari syndrome, has led to the belief that FNH is
caused by a hyperplastic response to a localized vascular abnormality
[2]. FNH is typically a
hypervascular lesion, and confident diagnosis and differentiation from other
hypervascular lesions (which include hemangioma, hepatocellular carcinoma,
hepatic adenoma, and hypervascular metastases) are essential because the
lesion is benign and almost always asymptomatic.
The characteristics of FNH on helical CT have been reported in the
literature [3,
4]. The lesion typically has a
smooth surface with an ill-defined margin unless a pseudocapsule is present;
is homogeneously hyperattenuating in the hepatic artery phase; and is
isoattenuating to the surrounding liver parenchyma on unenhanced, portal
venous, and delayed phases. A fibrous central scar had been reported in 35% of
lesions 3 cm or smaller and in 65% of lesions larger than 3 cm (Figs.
1A and
1B). When present, a central
scar is hypoattenuating to the surrounding lesion on hepatic arterial and
portal venous phases and typically shows enhancement on delayed (5-10 min)
images. Although most lesions are solitary, multiple FNH lesions have been
reported in up to 25% of cases
[1,
3] (Figs.
2A and
2B).
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Fig. 1A —39-year-old woman with focal nodular hyperplasia. Axial image in
arterial phase reveals hypervascular lesion in left lobe of liver
(arrow, A) that becomes isodense to liver parenchyma in portal
venous phase (B). Notice hypodense central scar (arrowheads,
B) and displacement of left hepatic vein (arrow, B) by
mass.
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Fig. 1B —39-year-old woman with focal nodular hyperplasia. Axial image in
arterial phase reveals hypervascular lesion in left lobe of liver
(arrow, A) that becomes isodense to liver parenchyma in portal
venous phase (B). Notice hypodense central scar (arrowheads,
B) and displacement of left hepatic vein (arrow, B) by
mass.
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Fig. 2A —32-year-old woman with focal nodular hyperplasia. Axial image in
arterial phase reveals multiple hypervascular lesions in both lobes of liver
(arrows, A) that become isodense to liver parenchyma in portal
venous phase (B).
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Fig. 2B —32-year-old woman with focal nodular hyperplasia. Axial image in
arterial phase reveals multiple hypervascular lesions in both lobes of liver
(arrows, A) that become isodense to liver parenchyma in portal
venous phase (B).
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The recent introduction of 16-MDCT has improved spatial and temporal
resolution compared with helical single-detector CT and has improved image
quality of CT, resulting in better characterization of the angioarchitecture
of hypervascular lesions [5].
Concurrent advances in workstation and computer technology have allowed
accurate analysis of large volumetric data sets. Exquisite delineation of
feeding arteries, draining veins, and tumor neovascularity is now possible
[5,
6]. The objective of this
article is to show the different imaging characteristics of FNH on 16-MDCT
angiography with advanced image processing. We present our personal experience
in demonstrating the imaging features of FNH in a series of patients referred
to us in routine clinical practice. Although some of these features can be
delineated in the axial plane, they may be more readily detected with image
processing. Familiarity with these features improves lesion characterization
and minimizes the need for additional unenhanced and delayed (5-10 min) phase
acquisitions, with the associated increased patient radiation dose. It also
reduces the need for follow-up imaging studies, percutaneous biopsy, or
surgery.
Imaging Protocol
Scanning was performed using the Sensation 16-MDCT scanner (Siemens Medical
Solutions). Gantry rotation time was 500 msec, with a detector collimation and
slice thickness of 0.75 mm for arterial and portal venous phase image
acquisition. Patients received 750 mL of water as a neutral contrast agent 15
min before the study and another 250 mL at the time of the study. Positive
oral contrast was not administered because it may degrade image
reconstruction. Patients also received 120-140 mL (2 mL/kg) of nonionic
contrast medium (iohexol, Omnipaque 350 mg/mL; Nycomed) injected IV at a rate
of 3-4 mL/sec with a power injector. The scan delay was 25-30 sec and 55-60
sec for the arterial and portal venous phases, respectively.
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Fig. 3A —30-year-old woman with predominantly exophytic focal nodular
hyperplasia (FNH). Coronal maximum-intensity-projection (MIP) image in
arterial phase shows large branch from right hepatic artery (arrow)
supplying center of lesion. Notice absence of short serpiginous vessels with
abrupt angulation, serrated appearance, and variable diameter to suggest
malignant vessels.
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Fig. 3B —30-year-old woman with predominantly exophytic focal nodular
hyperplasia (FNH). Coronal volume-rendered image in same phase (B)
shows tumor stain caused by feeding arteries dividing into smaller branches,
resulting in typical reticular (netlike) pattern. Notice fine peripheral
septations (arrowheads, B) characteristic of FNH. No
peritumoral enhancement seen. Coronal MIP (C) and volume-rendered
(D) images in portal venous phase show several large veins draining
into middle hepatic vein (arrow).
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Fig. 3C —30-year-old woman with predominantly exophytic focal nodular
hyperplasia (FNH). Coronal volume-rendered image in same phase (B)
shows tumor stain caused by feeding arteries dividing into smaller branches,
resulting in typical reticular (netlike) pattern. Notice fine peripheral
septations (arrowheads, B) characteristic of FNH. No
peritumoral enhancement seen. Coronal MIP (C) and volume-rendered
(D) images in portal venous phase show several large veins draining
into middle hepatic vein (arrow).
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Fig. 3D —30-year-old woman with predominantly exophytic focal nodular
hyperplasia (FNH). Coronal volume-rendered image in same phase (B)
shows tumor stain caused by feeding arteries dividing into smaller branches,
resulting in typical reticular (netlike) pattern. Notice fine peripheral
septations (arrowheads, B) characteristic of FNH. No
peritumoral enhancement seen. Coronal MIP (C) and volume-rendered
(D) images in portal venous phase show several large veins draining
into middle hepatic vein (arrow).
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Fig. 3E —30-year-old woman with predominantly exophytic focal nodular
hyperplasia (FNH). Coronal multiplanar reconstructed image in portal venous
phase shows hypodense central scar (arrow) typical of FNH. See also
Figures S3F and S3G, cine loops, in supplemental data online.
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Fig. 4A —41-year-old woman with focal nodular hyperplasia. Coronal
maximum-intensity-projection image in arterial phase shows large branch from
right hepatic artery supplying lesion. Notice central artery within scar
(arrowhead).
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Fig. 4B —41-year-old woman with focal nodular hyperplasia. Coronal
volume-rendered image in same phase shows lobular tumor with typical reticular
pattern of enhancement, central scar (arrowhead), and peripheral
septations (arrows).
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Image Processing
At our institution, image processing is performed using a commercially
available workstation and software (In Space Software, Leonardo workstation,
Siemens Medical Solutions). Real-time axial scrolling, multiplanar
reconstruction, interactive maximum-intensity-projection (MIP), and
volume-rendering techniques are used to scrutinize the hepatic parenchyma.
Slab MIP and volume rendering allow accurate delineation of the feeding
arteries, draining veins, tumor angioarchitecture, and central scar (Figs.
3A,
3B,
3C,
3D,
3E,
4A,
4B,
4C,
5A,
5B,
5C,
6A and
6B).
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Fig. 5A —28-year-old woman with focal nodular hyperplasia. Coronal
maximum-intensity-projection (MIP) image in arterial phase shows large branch
from left hepatic artery (arrow) supplying center of lesion. Notice
reticular pattern of enhancement and peripheral septations
(arrowheads).
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Fig. 5C —28-year-old woman with focal nodular hyperplasia. Axial multiplanar
reconstructed image in portal venous phase shows pseudocapsule
(arrows) and central scar (arrowhead).See also Figures S5D
and S5E, cine loops, in supplemental data online.
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Fig. 6A —49-year-old woman with focal nodular hyperplasia. Coronal
maximum-intensity-projection image in arterial phase shows small branch from
right hepatic artery (arrow) supplying dome lesion.
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Fig. 6B —49-year-old woman with focal nodular hyperplasia. Coronal
volume-rendered image in arterial phase shows reticular enhancement. Notice
presence of peripheral septations (arrows). See also Figures S6C and
S6D, cine loops, in supplemental data online.
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MDCT Angiography Features of FNH
Feeding Arteries
One or more enlarged feeding arteries can be identified depending on the
size of the lesion (Figs. 3A,
3B,
3C,
3D,
3E,
4A,
4B,
4C,
5A,
5B,
5C,
6A and
6B). Feeding arteries may be
peripheral, septal, or central in location within the lesion. The feeding
artery usually divides into small penetrating branches, resulting in a
reticular pattern (Figs. 7A,
7B,
7C,
7D,
8A,
8B,
8C,
8D,
9A,
9B and
9C). (Figures S3 and S5-S7 can
be seen in the AJR electronic supplement to this article, available
at
www.ajronline.org,
and present more detail than the figures printed here.) Central arteries may
be identified within a scar (Fig.
4A). No neovascularity in the form of short serpiginous vessels
with abrupt angulation, serrated appearance, and variable diameter is seen, as
these findings usually represent malignant vessels. Lesions are typically ill
defined, with no peritumoral enhancement (wedge-shaped or irregular
enhancement and opacification of vascular structures adjacent to the tumor),
as has been reported in hemangioma, hepatocellular carcinoma, and metastases
[7,
8]. The entire course of
feeding arteries can be easily delineated using sliding MIP images of the
arterial phase acquisition.
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Fig. 7A —35-year-old woman with focal nodular hyperplasia. Coronal
maximum-intensity-projection (MIP) image in arterial phase shows two branches
from right hepatic artery (arrows) supplying dome lesion.
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Fig. 7B —35-year-old woman with focal nodular hyperplasia. Axial oblique MIP
image with slightly different window setting shows small penetrating arterial
branches (arrowheads) resulting in reticular pattern of
enhancement.
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Fig. 7D —35-year-old woman with focal nodular hyperplasia. Surrounding
displaced veins and compressed hepatic parenchyma in C results in
pseudocapsule (arrows) in portal venous phase. See also Figures S7E
and S7F, cine loops, in supplemental data online.
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Fig. 8A —35-year-old woman with focal nodular hyperplasia. Coronal
maximum-intensity-projection image in arterial phase shows small branch from
replaced left hepatic artery (arrow) supplying dome lesion.
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Fig. 8B —35-year-old woman with focal nodular hyperplasia. Axial (B)
and coronal (C) multiplanar reconstructions in arterial phase show
reticular pattern of enhancement typical of focal nodular hyperplasia.
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Fig. 8C —35-year-old woman with focal nodular hyperplasia. Axial (B)
and coronal (C) multiplanar reconstructions in arterial phase show
reticular pattern of enhancement typical of focal nodular hyperplasia.
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Draining Veins
Several small anomalous sinusoids and draining veins may be identified
surrounding the FNH, and they become more confluent toward a hepatic vein.
Larger tumors can have several draining veins and can result in displacement
of major hepatic and portal venous branches due to mass effect (Figs.
3A,
3B,
3C,
3D,
3E,
4A,
4B,
4C,
5A,
5B,
5C,
7A,
7B,
7C and
7D). Portal venous drainage is
unusual in FNH [9] and is more
commonly seen in patients with hepatocellular carcinoma caused by significant
arteriovenous shunting. In our experience, hepatic venous drainage is best
shown on MIP images of the portal venous phase as the entire vessel course can
be delineated. On volume-rendered images, lesions show fine homogeneous
granularity or tumor blush resulting from accumulation of contrast material in
the tumor interstitium, often with a linear radiolucency due to a central
scar.
Pseudocapsule
This may appear as a thin hypodense rim in the arterial phase that becomes
hyperdense in the portal venous phase. This is particularly pronounced in
larger lesions and may be a result of dilated surrounding vessels or sinusoids
or compressed liver parenchyma
[3,
9,
10]. In our experience, a
pseudocapsule is best seen on volume-rendered images of the portal venous
phase acquisition (Figs. 4A,
4B,
4C,
5A,
5B,
5C, and
7A,
7B,
7C and
7D).
Central Scar
A scar is a region of low attenuation in or near the center of the lesion
and is best seen on volume-rendered images of the portal venous phase (Figs.
2A,
2B,
3A,
3B,
3C,
3D,
3E,
4A,
4B,
4C and
5A,
5B,
5C) because volume rendering
enhances the difference in attenuation between the central scar and the
surrounding tumor. A scar may extend through thin septations toward the
surface of the lesion. A feeding artery penetrating into a central scar can be
easily identified on MIP images of the arterial phase (Figs.
4A,
4B and
4C).
Septations
These are linear structures radiating from the central scar peripherally to
the surface of the lesion. They may be seen even if a central scar is absent
and can result in surface lobularity of the lesion. Similar to a central scar,
septations are best seen on volume-rendered images of the portal venous phase.
These are characteristic of FNH but are only reported in 8% of lesions,
according to one study [3].
However, in our experience, these septations are frequently detected with fine
manipulation of the degree of tissue opacity of the volume-rendered images
(Figs. 3A,
3B,
3C,
3D,
3E,
4A,
4B,
4C,
6A and
6B).
Conclusion
Sixteen-MDCT angiography with image processing is a powerful tool that can
harness data in axial images to aid in lesion characterization. Thorough
evaluation of angiographic features of FNH can help the differentiation of
this benign lesion from other hypervascular liver lesions without the need for
additional imaging, biopsy, or surgery.
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Abstract
Introduction
