DOI:10.2214/AJR.05.1093
AJR 2006; 187:W569-W575
© American Roentgen Ray Society
MRI of Takayasu's Arteritis: Typical Appearances and Complications
Eijun Sueyoshi1,
Ichiro Sakamoto1 and
Masataka Uetani1
1 All authors: Department of Radiology, Nagasaki University School of Medicine,
Sakamoto 1-7-1, Nagasaki 852-8501, Japan.
Received June 25, 2005;
accepted after revision August 12, 2005.
Address correspondence to E. Sueyoshi.
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Abstract
OBJECTIVE. Although Takayasu's arteritis (TA) is more common in
Asian countries, it has a worldwide distribution. MRI is widely used for its
diagnosis. Our purpose is to present a comprehensive pictorial review of its
typical appearances and complications on MRI.
CONCLUSION. MRI can effectively provide almost all anatomic
information in patients with TA. MRI is very useful for accurate diagnosis of
TA and its complications. Knowledge of MRI findings is essential for improving
patient outcome.
Keywords: cardiopulmonary imaging • cardiovascular disease • cardiovascular imaging • MRI
Introduction
Takayasu's arteritis (TA) is a primary arteritis of unknown cause that
commonly affects the aorta and its major branches and the pulmonary artery
[1-5].
CT and MRI are widely used for diagnosis of TA
[1-5].
Although CT is a useful technique for diagnosis of TA, MRI has several
advantages over CT. In this essay, we present a comprehensive pictorial review
of the typical appearances and complications of TA on MRI.
Clinical Features of TA
TA is more common in Asian countries, but it has a worldwide distribution.
The incidence in the United States was previously estimated at 2.6 cases per
one million population per year. Women comprise 80-90% of patients with TA,
contracting it mostly in the second and third decades of life. Men are rarely
affected [2].
In laboratory studies, concentrations of C-reactive protein might be
increased and the erythrocyte sedimentation rate might be accelerated, but
they correlate poorly with disease activity. Currently, no known serologic
test is able to supplant vascular histopathologic analysis in determining
active inflammation because TA has no specific serum markers
[2].
Histologically, TA is characterized by granulomatous inflammation of the
arterial wall with marked intimal proliferation and fibrosis of the media and
adventitia, which eventually leads to stenosis, occlusion, and, occasionally,
poststenotic dilatations and aneurysm formation (when inflammation destroys
the media) [2].
The clinical manifestations of TA are usually divided into early and late
phases, with a classic triphasic pattern of expression. This consists of an
early or prepulseless phase (characterized by nonspecific systemic features
such as low-grade fever, malaise, weight loss, and fatigue), a vascular
inflammatory phase, and a late quiescent and occlusive phase
[1,
2]. However, this sequential
presentation is likely to occur only in a minority of patients because the
disease is usually recurrent, leading to coexistence of various phases. A
variable interval (months to years) may separate acute from occlusive phases,
during which vascular insufficiency develops. Consequently, we recommend
follow-up imaging at least once a year. Symptoms of vascular compromise may be
minimized by the development of collateral circulation with the slow onset of
stenosis. The lack of specificity of early symptoms tends to delay the
diagnosis, which is most frequently made during the late stage
[1,
2,
6].
Characteristic features of the late phase include, for example, diminished
or absent pulses, vascular bruits, hypertension (as a consequence of renal
artery stenosis), mesenteric angina, retinopathy, aortic regurgitation (when
the ascending aorta is involved), and neurologic symptoms secondary to
hypertension or ischemia (postural dizziness, seizures, amaurosis).
Clinically, hypertension, stroke, and aortic insufficiency warrant close
attention, as these vascular complications often become fatal
[2,
6].
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Fig. 1B —23-year-old man with Takayasu's arteritis in acute phase.
Axial T1-weighted image (TR/TE, 800/14) shows improvement of wall thickening
of ascending aorta and pulmonary artery after steroid therapy.
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Fig. 2B —24-year-old woman with Takayasu's arteritis in acute phase.
Fat-suppressed contrast-enhanced T1-weighted image (TR/TE, 550/14) shows
thickening and enhancement of wall of aortic branches. Fat-suppressed
contrast-enhanced T1-weighted image can well depict enhancement of arterial
wall because of active inflammation.
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Therapy depends on the degree of disease activity, as well as on the
complications that may develop. The most important aspects of treatment are to
control active inflammation and to prevent further vascular damage. High-dose
corticosteroids are the mainstay of TA therapy, which is usually continued for
1 year after remission and then tapered to discontinuation. Treatment of
symptomatic fibrotic lesions (stenoses or occlusions) requires either
interventional or surgical therapy. This can be achieved by angioplasty with
or without stenting, or, in severe cases, by vascular resection and surgical
placement of composite graft
[2,
5].
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Fig. 3A —30-year-old woman with Takayasu's arteritis in acute phase.
Contrast-enhanced 3D MR angiography (TR/TE, 6.1/1.4; flip angle, 20°)
shows complete occlusion of right pulmonary, left common carotid, and left
subclavian arteries. Sometimes occlusion of pulmonary artery and aortic
branches is seen in acute phase.
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Fig. 4 —30-year-old woman with Takayasu's arteritis in acute phase.
Axial T1-weighted images (TR/TE, 923/20) show pseudoaneurysm arising from
aortic arch. Mild wall thickening of descending aorta is also seen. In
Takayasu's arteritis, pseudoaneurysm formation is sometimes seen in acute
phase.
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MRI of TA
Conventional angiography has been regarded as necessary for the diagnosis
of TA and its complications. Recently, however, CT and MRI (including CT and
MR angiography) were shown clearly to delineate aortic mural changes that are
difficult to detect on conventional angiography. Hence, these techniques are
alternatives to conventional angiography
[2-4].
MRI has several advantages over CT: paramagnetic contrast media rarely
cause anaphylactic reactions and are nonnephrotoxic, ionizing irradiation is
not used, soft-tissue differentiation is better, MRI has increased sensitivity
in the detection of mural edema, and cine MRI depicts aortic regurgitation.
However, MRI also has disadvantages, including difficulty in visualizing small
branch vessels and poor visualization of vascular calcification. If
visualization of small branch vessels or vascular calcification is needed,
additional examinations may be required
[5]. In addition, MR
angiography may falsely accentuate the degree of vascular stenoses
[5].
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Fig. 5A —53-year-old woman with Takayasu's arteritis in late phase.
Contrast-enhanced 3D MR angiography (TR/TE, 5.9/1.2; flip angle, 20°)
shows dilatation of ascending aorta. Diffuse narrowing of descending thoracic
aorta is also seen.
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Fig. 5B —53-year-old woman with Takayasu's arteritis in late phase.
Contrast-enhanced 3D MR angiography (TR/TE, 5.9/1.2; flip angle, 20°)
shows diffuse narrowing of abdominal aorta. These findings are typical
features of aorta in late phase of Takayasu's arteritis.
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Fig. 6B —27-year-old woman with Takayasu's arteritis in late phase.
Cine MR image (TR/TE, 5.2/1.8; flip angle, 30°) shows broad signal void
(arrow) from aortic valve to left ventricle, suggesting aortic
regurgitation.
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Fig. 7 —29-year-old woman with Takayasu's arteritis and renal
hypertension in late phase. Contrast-enhanced 3D MR angiography (TR/TE,
5.9/1.2; flip angle, 20°) shows severe stenosis of right renal artery,
which is nearly occluded (arrow).
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Fig. 8 —59-year-old woman with Takayasu's arteritis in late phase.
Contrast-enhanced 3D MR angiography (TR/TE, 8.6/1.8; flip angle, 20°)
shows occlusion of proximal portion of left subclavian artery
(arrow). Left subclavian artery is opacified via left vertebral
artery (subclavian steal syndrome, arrowheads).
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MR Technique
MRI was conducted using a 1.5-T MR unit (GE Healthcare). We followed
routine MR techniques at our institution.
The entire aorta—from its root to bifurcation—is imaged in the
axial or left anterior oblique-equivalent plane or both using the spin-echo or
black blood technique. Two-dimensional contrast-enhanced (0.1 mmol/kg;
gadopentetate dimeglumine [Magnevist], Nihon-Schering) subtracted perfusion
(fast spoiled gradient-recalled echo) images of the pulmonary artery (TR/TE,
5.3/1.3; flip angle, 30°; receiver bandwidth, 31.25 kHz/pixel; and
acquisition time, 0.7 sec) are obtained to detect any pulmonary parenchymal
defect caused by pulmonary artery obstruction. Based on the circulation time
determined from the 2D contrast-enhanced perfusion images, 3D
contrast-enhanced (0.1 mmol/kg; gadopentetate dimeglumine [Magnevist],
Nihon-Schering) MR angiography of the thoracic aorta and pulmonary artery is
performed to evaluate luminal narrowing or dilatation. If MR angiography of
the abdominal aorta is required, we perform two injections of contrast media
and obtain separate MR angiograms of the thoracic and abdominal aortas. The
imaging time per measurement is 22 seconds during a breath-hold. Neither
cardiac nor respiratory gate is used. The entire aorta is imaged on the axial
plane using a fat-suppressed T1-weighted fast spin-echo technique to detect
enhancement of the vessel wall. If MRI shows dilatation of the ascending
aorta, additional cine MRI of the heart is performed to detect aortic
regurgitation.
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Fig. 9A —41-year-old woman with Takayasu's arteritis in late phase.
Contrast-enhanced 3D MR angiography (TR/TE, 7.1/1.4; flip angle, 20°)
shows occlusion of left subclavian artery. Irregularities of vessel lumen of
other aortic branches are also shown.
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Fig. 9B —41-year-old woman with Takayasu's arteritis in late phase.
FLAIR images of brain (TR/TE, 8002/114; TI, 2000) show brain atrophy caused by
chronic ischemia because of occlusion and stenoses of aortic branches. High
signal spots are seen in deep white matter, suggesting small infarctions.
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Fig. 9C —41-year-old woman with Takayasu's arteritis in late phase.
FLAIR images of brain (TR/TE, 8002/114; TI, 2000) show brain atrophy caused by
chronic ischemia because of occlusion and stenoses of aortic branches. High
signal spots are seen in deep white matter, suggesting small infarctions.
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Fig. 10 —52-year-old man with Takayasu's arteritis in late phase.
Contrast-enhanced 3D MR angiography (TR/TE, 6.1/1.3; flip angle, 20°)
shows segmental septa of the right innominate artery (arrow). This
finding is characteristic of Takayasu's arteritis.
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MRI Features of Acute Phase
Significant findings of the acute phase of TA are wall thickening of the
aorta and pulmonary artery (Figs.
1A and
1B)
[1-5].
Thickened wall is enhanced on gadolinium-enhanced images (Figs.
2A and
2B)
[2,
5]. These findings suggest
active inflammation. A recent report suggests that delayed contrast-enhanced
MRI may also be a useful technique to identify inflammation in the arterial
wall [7]. Sometimes, occlusion
of the aortic branches or pulmonary artery or both is seen in the acute phase
(Figs. 3A,
3B, and
3C). Rarely, pseudoaneurysm
formation occurs as in the acute phase
(Fig. 4)
[4].
MRI Features of Late Phase
Significant findings of the late phase of TA include diffuse narrowing of
the descending thoracic and abdominal aorta. Dilatation occurs most commonly
in the ascending aorta [1,
2,
4]. MR angiography depicts
these findings well (Figs. 5A
and 5B). Cine MRI depicts
aortic regurgitation caused by dilatation of the ascending aorta (Figs.
6A and
6B)
[4].
Stenotic lesions of aortic branches and pulmonary artery commonly occur in
the late phase. The lesions typically occur in the proximal portions of the
branches [1,
2,
4]. Stenosis, the most common
finding, involves all arteries arising from the aorta, most commonly the
common carotid and subclavian arteries. Occlusion is the second most common
finding. Abrupt occlusion, abrupt transition to collateral vessels, and
flame-shaped termination are characteristic. In the abdominal aorta, the renal
artery is the most frequently involved branch
[1,
4] (Figs.
7,
8,
9A,
9B,
9C, and
10). Pulmonary artery
involvement is relatively high, with an estimated occurrence rate of 50-80%
[1,
4]. Pulmonary perfusion
scintigraphy or conventional angiography or both, including digital
subtraction angiography, are useful methods for detecting obstructive changes
of the pulmonary artery [2,
8]. Recently, it was shown that
MR angiography and MR perfusion imaging can depict these findings (Figs.
4,
11A, and
11B)
[3].
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Fig. 11A —23-year-old woman with Takayasu's arteritis in late phase. 2D
contrast-enhanced MR perfusion images (TR/TE, 5.3/1.3; flip angle, 30°)
shows obstructive lesion in left middle lung field (arrow).
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Fig. 11B —23-year-old woman with Takayasu's arteritis in late phase.
Pulmonary perfusion scintigrams in anterior projections show perfusion defects
in left middle lung field (arrow). This finding correlates with MR
perfusion image.
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Fig. 12A —50-year-old woman with Takayasu's arteritis in late phase.
Axial T1-weighted image (TR/TE, 576/14) shows aortic dissection in descending
aorta. False lumen with mural thrombus (F) is markedly dilated. True lumen is
compressed by false lumen (arrow).
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Fig. 12B —50-year-old woman with Takayasu's arteritis in late phase.
Multiplanar reconstruction (MPR) image obtained from source images of
contrast-enhanced 3D MR angiography (TR/TE, 6.1/1.3; flip angle, 20°)
shows an entry site (arrow).
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TA is also associated with aortic dissection and pseudoaneurysm formation
in the late phase. MR angiography is also useful for evaluation of bypass
graft (Figs. 12A,
12B,
13A,
13B,
13C, and
13D)
[2,
4,
5].
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Fig. 13A —55-year-old woman with Takayasu's arteritis in late phase.
This patient underwent bypass graft for occlusion of left carotid and
subclavian arteries. Contrast-enhanced 3D MR angiography (TR/TE, 6.0/1.2; flip
angle, 20°) shows patency of bypass graft, connecting left femoral, left
carotid, and left subclavian arteries.
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Fig. 13B —55-year-old woman with Takayasu's arteritis in late phase.
This patient underwent bypass graft for occlusion of left carotid and
subclavian arteries. Contrast-enhanced 3D MR angiography (TR/TE, 6.0/1.2; flip
angle, 20°) shows patency of bypass graft, connecting left femoral, left
carotid, and left subclavian arteries.
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Fig. 13C —55-year-old woman with Takayasu's arteritis in late phase.
This patient underwent bypass graft for occlusion of left carotid and
subclavian arteries. Contrast-enhanced 3D MR angiography (TR/TE, 6.0/1.2; flip
angle, 20°) shows patency of bypass graft, connecting left femoral, left
carotid, and left subclavian arteries.
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Fig. 13D —55-year-old woman with Takayasu's arteritis in late phase.
Three years later, axial T1-weighted image (TR/TE, 600/14) shows
pseudoaneurysm at anastomosis site of left subclavian artery caused by
weakness of arterial wall (arrow).
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Conclusion
MRI is very useful in the accurate diagnosis of TA, and in a patient with
TA, can provide almost all the anatomic information needed to enable early
treatment and improve patient outcome. MRI may be the only technique needed
for diagnosis of TA and its complications during the follow-up period.
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Abstract
Introduction
