DOI:10.2214/AJR.08.1027
AJR 2008; 191:1581-1588
© American Roentgen Ray Society
Time-Resolved MR Angiography of the Central Veins of the Chest
Charles Y. Kim1 and
Elmar M. Merkle
1 Both authors: Department of Radiology, Duke University Medical Center, Box
3808, Durham, NC 27710.
Received April 6, 2008;
accepted after revision May 29, 2008.
E. M. Merkle receives research support from Siemens Medical Solutions.
CME
This article is available for CME credit.
See
www.arrs.org
for more information.
Address correspondence to E. M. Merkle
(elmar.merkle{at}duke.edu).
Abstract
OBJECTIVE. The purpose of our study was to show the usefulness and
limitations of contrast-enhanced time-resolved MR angiography (MRA) for
imaging the central veins of the chest.
CONCLUSION. Time-resolved MRA is highly sensitive for the detection
of abnormalities and is particularly useful in conjunction with static
high-spatial-resolution MRA. However, several intrinsic limitations must be
kept in mind.
Keywords: central veins • chest • MRA • time-resolved MRA
Introduction
Static high-spatial-resolution contrast-enhanced MR angiography (MRA) has
been shown to be equally sensitive and specific for revealing stenoses and
occlusions as conventional venography of the central veins of the chest
[1–5].
Time-resolved MRA shows the dynamics of blood flow in a manner similar to
conventional angiography, by the rapid acquisition of sequential images. As a
stand-alone sequence, time-resolved MRA of the central veins of the chest has
an extremely high sensitivity that is equal to that of high-spatial-resolution
MRA for the detection of central venous stenoses and occlusions, but with a
markedly lower specificity. However, time-resolved MRA has been shown to be a
useful adjunct to the conventionally acquired static high-spatial-resolution
MR data set by improving specificity for detecting occlusions and enhancing
reviewer confidence without increasing the overall study interpretation time
[6]. In addition, time-resolved
MRA may be useful as an initial screening examination for patients with a low
pretest probability of central venous abnormalities that could markedly reduce
the gadolinium dose and therefore possibly decrease the chances for subsequent
development of nephrogenic systemic fibrosis
[6].
Common indications for MRA of the central veins of the chest include
superior vena cava (SVC) syndrome and evaluation of potential venous access
sites, particularly for hemodialysis patients. This article will show the
clarity and nuances with which time-resolved MRA displays central venous
abnormalities. In addition, the various limitations and drawbacks will also be
discussed.
Technique
A number of time-resolved angiographic sequences are currently in use,
including TREAT (time-resolved echo-shared angiographic technique) (Siemens
Medical Solutions), time-resolved angiography with interleaved stochastic
trajectories (TWIST) (Siemens), time-resolved imaging of contrast kinetics
(TRICKS) (GE Healthcare), and 4D TRAK (time-resolved angiography using
keyhole) (Philips Healthcare). In these dynamic sequences, imaging of the
central veins of the chest is performed at rapid 2- to 5-second intervals,
typically for 1–3 minutes after the IV injection of 5–10 mL of a
gadolinium chelate followed by a saline bolus of at least 20 mL. Gadolinium
can be administered via a peripheral IV catheter or central venous catheter
(CVC). MRI is performed in the coronal orientation with postacquisition
processing into one coronal maximum-intensity-projection (MIP) image per time
point.
Normal Studies
The initial inflow phase images show the gadolinium bolus as it courses
from the peripheral IV injection site to the heart
(Fig. 1A; see also
www.ajronline.org
for sup plemental AVI images of this and all other figures in this article).
If gadolinium is administered via a CVC, right-heart opacification will be
visual ized without peripheral or central vein opacification
(Fig. 1B). The contrast bolus
should then quickly opacify the pulmonary vasculature, left heart, and aorta.
The arterial phase images are crucial for the discrimination of arteries from
veins because the arteries tend to have some degree of residual opacification
throughout the remainder of the study (Fig.
1C). During the venous phase, the central veins are maximally
opacified (Fig. 1C). If a
peripheral IV catheter is used for contrast injection, the ipsilateral central
venous system will be opacified twice, first during the contrast inflow to the
heart from the injection site, and again when the re circulated contrast agent
opacifies the venous system. For this reason, if a particular side is of
interest, it may be advantageous to use an ipsilateral arm peripheral IV
catheter. Previous reports have advocated use of a right arm peripheral IV
catheter because of the potential occurrence of concentrated gadolinium stasis
in the left brachiocephalic and subclavian veins with resultant susceptibility
artifact [7,
8]. However, those studies from
the late 1990s were performed without dual-power injectors and saline chaser
boluses after gadolinium injection, which are now commonly used. Therefore,
this phenomenon is no longer a common issue.
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Fig. 1A —Time-resolved MR angiography (MRA) of normal central veins in
73-year-old woman. See also Figure S1, AVI images, at
www.ajronline.org.
Inflow phase image shows gadolinium injection into right arm peripheral IV
catheter and opacification of right subclavian vein, right brachiocephalic
vein, superior vena cava (SVC), right heart, and pulmonary arteries.
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Fig. 1C —Time-resolved MR angiography (MRA) of normal central veins in
73-year-old woman. See also Figure S1, AVI images, at
www.ajronline.org.
Venous phase image shows mild diffuse narrowing of left internal jugular vein
(arrow) with no collaterals. Right internal jugular, bilateral
subclavian, and bilateral brachiocephalic veins as well as SVC are all widely
patent. Note mild residual opacification of heart, arteries, and pulmonary
vessels.
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Stenosis and Occlusion
The spatial resolution, although low, is usually adequate to characterize
the general morphology and degree of stenosis. The extent of associated
collateral formation can help to determine the hemodynamic significance and
chronicity. Therefore, non visualization of a central vein in combination with
enlarged, well-developed bypassing collaterals is consistent with a chronic
occlusion (Figs. 2A,
2B and
3A,
3B,
3C,
3D), whereas the presence of
luminal narrowing with local collaterals implies a hemodynamically significant
stenosis (Fig. 4A,
4B). Acute occlusions will
usually show less-developed or absent collateral veins (Fig.
5A,
5B,
5C).
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Fig. 2A —Chronic occlusion of right internal jugular vein shown on MR
angiography in 63-year-old woman with end-stage renal disease and history of
multiple prior central venous catheters. See also Figure S2, AVI images, at
www.ajronline.org.
Arterial phase image shows residual opacification of right subclavian vein
from right arm injection.
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Fig. 2B —Chronic occlusion of right internal jugular vein shown on MR
angiography in 63-year-old woman with end-stage renal disease and history of
multiple prior central venous catheters. See also Figure S2, AVI images, at
www.ajronline.org.
Venous phase image shows abrupt nonvisualization of right internal jugular
vein (asterisk) with large collateral vein (arrow) to right
subclavian vein, consistent with longstanding chronic occlusion. Left internal
jugular vein is not visualized but has multiple smaller left neck collaterals
(arrowheads), suggestive of subacute occlusion. Left brachiocephalic
vein is not visualized and is shown to be severely stenotic on
high-spatial-resolution images (not shown). Left subclavian vein is not
visualized but is shown to be widely patent on high-spatial-resolution images
(not shown), likely secondary to physiologically slow flow.
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Fig. 3A —Chronic subtotal occlusion of superior vena cava (SVC) and
marked azygous collateralization shown on MR angiography in 16-year-old girl
with sickle cell anemia and history of multiple central venous catheters. See
also Figure S3, AVI images, at
www.ajronline.org.
Early inflow phase image shows left arm peripheral IV injection with minimal
flow through nearly occluded SVC (thick arrow) and prompt filling of
markedly enlarged collateralized azygous vein (thin arrow).
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Fig. 3B —Chronic subtotal occlusion of superior vena cava (SVC) and
marked azygous collateralization shown on MR angiography in 16-year-old girl
with sickle cell anemia and history of multiple central venous catheters. See
also Figure S3, AVI images, at
www.ajronline.org.
Late inflow phase image shows filling of inferior vena cava and right atrium
via azygous vein.
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Fig. 3C —Chronic subtotal occlusion of superior vena cava (SVC) and
marked azygous collateralization shown on MR angiography in 16-year-old girl
with sickle cell anemia and history of multiple central venous catheters. See
also Figure S3, AVI images, at
www.ajronline.org.
Arterial phase image.
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Fig. 3D —Chronic subtotal occlusion of superior vena cava (SVC) and
marked azygous collateralization shown on MR angiography in 16-year-old girl
with sickle cell anemia and history of multiple central venous catheters. See
also Figure S3, AVI images, at
www.ajronline.org.
Venous phase image shows patency of left internal jugular, subclavian, and
brachiocephalic veins and near occlusion of SVC. Note nonopacification of
right central veins. High-spatial-resolution images (not shown) showed
occlusion of right subclavian, internal jugular, and brachiocephalic
veins.
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Fig. 4B —Severe stenosis of right internal jugular vein shown on MR
angiography in 62-year-old man with lung cancer. See also Figure S4, AVI
images, at
www.ajronline.org.
Venous phase image shows severe narrowing of right internal jugular vein
(arrowhead) and collateral flow via asymmetrically prominent right
external jugular vein (arrow).
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Fig. 5A —Suboptimal visualization of deep vein thrombosis in right
subclavian vein on time-resolved maximum-intensity-projection MR angiography
images in 64-year-old woman with cholangiocarcinoma. See also Figure S5, AVI
images, at
www.ajronline.org.
Arterial phase image shows no residual opacification of any venous structures,
consistent with injection via central venous catheter.
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Fig. 5B —Suboptimal visualization of deep vein thrombosis in right
subclavian vein on time-resolved maximum-intensity-projection MR angiography
images in 64-year-old woman with cholangiocarcinoma. See also Figure S5, AVI
images, at
www.ajronline.org.
Venous phase image shows nonvisualization of right subclavian vein (thick
arrow) despite opacification of left subclavian vein, with no significant
collateral vein opacification to suggest chronic occlusion. Although this
suggests acute occlusion, technical issues cannot be excluded as cause of
nonvisualization, as discussed previously. Note narrow, late-filling left
internal jugular vein (thin arrow) and prominent collateralized left
external jugular vein (arrowhead), suggesting chronic stenosis of
left internal jugular vein. Although not evident on this low-resolution image,
severe stenosis at its origin is confirmed on high-spatial-resolution images
(not shown).
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Fig. 5C —Suboptimal visualization of deep vein thrombosis in right
subclavian vein on time-resolved maximum-intensity-projection MR angiography
images in 64-year-old woman with cholangiocarcinoma. See also Figure S5, AVI
images, at
www.ajronline.org.
Static high-spatial-resolution image shows prominent, nearly occlusive filling
defect in origin of right subclavian vein (arrow), allowing confident
diagnosis of venous thrombosis as cause of nonvisualization.
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Vascular Anomalies
Venous anomalies can be easily detected on high-spatial-resolution images.
However, the time-resolved component is particularly helpful for showing the
route and degree of preferential blood flow. Anomalies such as left-sided SVC,
duplicated SVC, and partial anomalous pulmonary venous return can be detected
(Fig. 6A,
6B,
6C).
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Fig. 6A —Partial anomalous pulmonary venous return shown on MR
angiography in 48-year-old man with end-stage renal disease and history of
multiple central venous catheters. See also Figure S6, AVI images, at
www.ajronline.org.
Inflow phase image shows left brachiocephalic vein and superior vena cava,
right heart, and pulmonary artery opacification.
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Fig. 6B —Partial anomalous pulmonary venous return shown on MR
angiography in 48-year-old man with end-stage renal disease and history of
multiple central venous catheters. See also Figure S6, AVI images, at
www.ajronline.org.
Arterial phase image also shows opacification of left upper lobe pulmonary
vein (arrow).
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Fig. 6C —Partial anomalous pulmonary venous return shown on MR
angiography in 48-year-old man with end-stage renal disease and history of
multiple central venous catheters. See also Figure S6, AVI images, at
www.ajronline.org.
Venous phase image shows left upper lobe pulmonary vein (thin arrow)
draining into left brachiocephalic vein. Also note right brachiocephalic vein
occlusion (thick arrow) and multiple collateral veins
(arrowheads).
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Vascular Tumors
Vascular masses may be visualized with time-resolved MRA, and their effect
on the central veins can be evaluated for presurgical planning. In addition,
the enhancement dynamics of vascular masses may be assessed, which is less
appreciable on sequential static imaging (Fig.
7A,
7B,
7C).
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Fig. 7A —Vascular tumor (non–small cell lung carcinoma) in left
upper lobe invading anterior chest wall and compressing left central veins
shown on MR angiography in 49-year-old woman. See also Figure S7, AVI images,
at
www.ajronline.org.
Arterial phase image shows patent left subclavian artery. Note faint tumor
enhancement (arrow) that is less pronounced than that of nearby
thyroid gland.
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Fig. 7B —Vascular tumor (non–small cell lung carcinoma) in left
upper lobe invading anterior chest wall and compressing left central veins
shown on MR angiography in 49-year-old woman. See also Figure S7, AVI images,
at
www.ajronline.org.
Early venous phase image better shows vascular mass (thick arrows)
overlying left subclavian vessels and causing mild narrowing of left
brachiocephalic vein (thin arrow). Left subclavian vein is
suboptimally opacified and not visualized in region of mass.
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Fig. 7C —Vascular tumor (non–small cell lung carcinoma) in left
upper lobe invading anterior chest wall and compressing left central veins
shown on MR angiography in 49-year-old woman. See also Figure S7, AVI images,
at
www.ajronline.org.
Late venous phase image shows persistent opacification of vascular mass and
late opacification of left arm veins. Left subclavian vein abruptly terminates
in region of vascular mass, consistent with subtotal to complete occlusion
(arrow). Note that right subclavian vein is not visualized throughout
this study, although it was shown to be widely patent on
high-spatial-resolution images (not shown).
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Metallic Stent Artifact
Susceptibility artifacts secondary to metallic intravascular stents vary on
the basis of the metallic alloy composition and may preclude visualization of
the vessel lumen on most MRI sequences. However, time-resolved MRA can provide
information on stent patency that is often unattainable from static
high-spatial-resolution images. By examining local collaterals and the
temporal appearance of contrast material proximal and distal to the stent, the
presence or absence of a complete or subtotal occlusion can be inferred,
although the actual degree of in-stent stenosis cannot be accurately
determined (Fig. 8A,
8B,
8C,
8D). For the reasons described
previously, contrast material should be injected into the upper extremity
ipsilateral to the stent of concern. In the case of bilateral subclavian vein
metallic stents, a bilateral contrast injection may be considered
[9].
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Fig. 8A —Visualization of stent patency on MR angiography despite
in-stent signal void due to eddy currents in 31-year-old woman with sickle
cell anemia and stenoses of superior vena cava (SVC) and bilateral
brachiocephalic vein after stenting. See also Figure S8, AVI images, at
www.ajronline.org.
Chest radiograph shows partly MR-compatible stent (arrows) in
bilateral brachiocephalic veins extending into SVC.
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Fig. 8B —Visualization of stent patency on MR angiography despite
in-stent signal void due to eddy currents in 31-year-old woman with sickle
cell anemia and stenoses of superior vena cava (SVC) and bilateral
brachiocephalic vein after stenting. See also Figure S8, AVI images, at
www.ajronline.org.
In initial inflow image, left axillary and subclavian veins are opacified by
left arm peripheral IV injection with nonvisualization of segment of left
brachiocephalic vein and SVC due to metallic stent susceptibility artifact
(arrows). However, right heart is already opacified without
significant collateral veins, ruling out subtotal or complete in-stent
occlusion.
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Fig. 8C —Visualization of stent patency on MR angiography despite
in-stent signal void due to eddy currents in 31-year-old woman with sickle
cell anemia and stenoses of superior vena cava (SVC) and bilateral
brachiocephalic vein after stenting. See also Figure S8, AVI images, at
www.ajronline.org.
Arterial phase image.
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Fig. 8D —Visualization of stent patency on MR angiography despite
in-stent signal void due to eddy currents in 31-year-old woman with sickle
cell anemia and stenoses of superior vena cava (SVC) and bilateral
brachiocephalic vein after stenting. See also Figure S8, AVI images, at
www.ajronline.org.
Venous phase image shows right brachiocephalic nonvisualization at site of
right brachiocephalic stent, but with visualization of multiple associated
venous collaterals (arrows), suggestive of right brachiocephalic
stent stenosis or occlusion.
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Limitations
Suboptimal Subclavian Vein Assessment
The subclavian vein contralateral to the upper extremity used for
peripheral IV injection often shows poor or delayed enhancement compared with
the remainder of the central veins of the chest (Fig.
9A,
9B,
9C). This phenomenon is likely
due to physiologic slow venous return from the arms due to the patient's
immobility and arm positioning.
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Fig. 9B —Limited and delayed visualization of subclavian veins on MR
angiography in 45-year-old woman with normal central veins. Central venous
catheter was used for contrast injection. See also Figure S9, AVI images, at
www.ajronline.org.
Mid venous phase image shows normal bilateral internal jugular veins, normal
right brachiocephalic vein, and superior vena cava. Note that left
brachiocephalic vein is not well seen on this image, although it was shown to
be normal on high-spatial-resolution images (not shown).
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Fig. 9C —Limited and delayed visualization of subclavian veins on MR
angiography in 45-year-old woman with normal central veins. Central venous
catheter was used for contrast injection. See also Figure S9, AVI images, at
www.ajronline.org.
Late venous phase image approximately 15 seconds after B shows maximum
but poor opacification of bilateral subclavian veins (arrows).
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Suboptimal Left Brachiocephalic Vein Assessment
Because the 3D structures are depicted in 2D on the MIP images, the left
brachiocephalic vein may occasionally be poorly visualized (Fig.
10A,
10B,
10C,
10D) as a result of the
residual opacification of the superimposed aortic arch and great vessels. Poor
left brachiocephalic vein visualization has also been attributed to its
position between the aortic arch and the sternum, where it can be transiently
compressed during deep inspiration and particularly during breath-holding
[8,
10]. Therefore, if neither
side is of particular interest, placement of a left-sided peripheral IV
catheter will be beneficial because the right brachiocephalic vein is not
affected by these two factors. Again, this is contrary to outdated guidelines,
in which a right upper extremity peripheral IV catheter was advocated.
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Fig. 10A —Poor visualization of left brachiocephalic vein on MR
angiography in 53-year-old woman with breast cancer. See also Figure S10, AVI
images, at
www.ajronline.org.
Inflow phase image after injection into left arm IV catheter shows
opacification of left subclavian vein, left brachiocephalic vein
(arrow), and superior vena cava (SVC), all of which are widely
patent.
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Fig. 10C —Poor visualization of left brachiocephalic vein on MR
angiography in 53-year-old woman with breast cancer. See also Figure S10, AVI
images, at
www.ajronline.org.
Early venous phase image shows opacification of bilateral internal jugular
veins, left subclavian vein, right brachiocephalic vein, and SVC, but poor
opacification of left brachiocephalic vein (arrow) despite previously
shown patency. This may be at least partially attributable to overlapping
aortic arch opacification.
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Fig. 10D —Poor visualization of left brachiocephalic vein on MR
angiography in 53-year-old woman with breast cancer. See also Figure S10, AVI
images, at
www.ajronline.org.
Late venous phase image shows persistently poor opacification of left
brachiocephalic vein (arrow) despite minimal aortic arch
opacification, likely because of transient compression between aorta and
sternum. Note that right subclavian vein is not well opacified on any images,
although it was widely patent on high-spatial-resolution images (not
shown).
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Extensive Central Venous Occlusions
Although time-resolved MRA is highly sensitive for the detection of
abnormalities, the presence of multiple venous stenoses and occlusions can
result in markedly limited visualization of the central veins as a result of
severely impaired venous flow central to the lesion (Fig.
11A,
11B). This issue tends to be
more pronounced when the stenoses and occlusions are acute, before the
formation of venous collaterals.
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Fig. 11A —Multiple central venous occlusions shown on MR angiography in
67-year-old woman with metastatic lung cancer and multiple prior central
venous catheters who is presenting with acute right arm and facial swelling.
See also Figure S11, AVI images, at
www.ajronline.org.
Arterial phase image. Note suboptimal patient positioning due to severe
scoliosis.
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Fig. 11B —Multiple central venous occlusions shown on MR angiography in
67-year-old woman with metastatic lung cancer and multiple prior central
venous catheters who is presenting with acute right arm and facial swelling.
See also Figure S11, AVI images, at
www.ajronline.org.
Venous phase image shows nonvisualization of any normal central veins and
opacification of various collateral veins, including hemiazygous system
(arrow). High-spatial-resolution images (not shown) showed subtotal
occlusions of brachiocephalic veins and superior vena cava, with patent but
diffusely narrow bilateral subclavian and left internal jugular veins and
occluded right internal jugular vein.
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Deep Venous Thrombosis
As a result of the limited spatial resolution, identification of thrombus
as the cause of a stenosis or occlusion is often difficult with time-resolved
MRA (Fig. 5A,
5B,
5C).
MIP Field of View
A standardized field of view in the anteroposterior dimension is often
selected on the basis of the typical location of the central veins of the
chest to optimize temporal resolution. However, in cases of central venous
occlusion with extensive collateralization, some of the collateral veins may
not be completely in the field of view as a result of an excessively anterior
or posterior location, causing the artificial appearance of stenosis or
occlusion (Fig. 12A,
12B,
12C,
12D). Often, a true occlusion
can be excluded by examining the timing of vessel opacification proximal and
distal to the pseudoocclusion.
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Fig. 12A —Superior vena cava (SVC) occlusion and pseudoocclusion of
enlarged azygous vein collateral shown on MR angiography in 41-year-old woman
with end-stage renal disease
[6]. See also Figure S12, AVI
images, at
www.ajronline.org.
Coronal high-spatial-resolution image shows narrowing and irregularity of SVC
(arrow), although it is not clear whether severe stenosis or complete
occlusion is present because of motion artifact and volume averaging with
adjacent pulmonary veins.
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Fig. 12B —Superior vena cava (SVC) occlusion and pseudoocclusion of
enlarged azygous vein collateral shown on MR angiography in 41-year-old woman
with end-stage renal disease
[6]. See also Figure S12, AVI
images, at
www.ajronline.org.
Initial inflow phase image shows opacification of right subclavian and
brachiocephalic veins, with abrupt termination of mid-SVC (thick
arrow) and opacification of markedly enlarged azygous vein (thin
arrows) that is nonopacified in its central portion.
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Fig. 12C —Superior vena cava (SVC) occlusion and pseudoocclusion of
enlarged azygous vein collateral shown on MR angiography in 41-year-old woman
with end-stage renal disease
[6]. See also Figure S12, AVI
images, at
www.ajronline.org.
Immediately subsequent inflow phase image shows opacification of inferior vena
cava, right heart, and pulmonary arteries, consistent with chronic total
occlusion of SVC.
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Fig. 12D —Superior vena cava (SVC) occlusion and pseudoocclusion of
enlarged azygous vein collateral shown on MR angiography in 41-year-old woman
with end-stage renal disease
[6]. See also Figure S12, AVI
images, at
www.ajronline.org.
High-resolution image shows complete patency of enlarged azygous vein
(arrow). This falsely apparent occlusion on time-resolved
maximum-intensity-projection images is caused by exclusion of this very
posterior structure from anteroposterior field of view. However, because of
simultaneous opacification of both segments depicted on time-resolved
technique, it can be safely inferred that nonopacification is merely
artifactual.
|
|
Timing of Image Acquisition
In the presence of severe congestive heart failure or multiple venous
occlusions, the contrast bolus may not have sufficient time to cycle through
the arterial system and back into the central veins during the routine timed
acquisitions. Therefore, in these cases a longer acquisition time may be
beneficial.
Conclusion
Time-resolved MRA is a useful technique for evaluating the central veins of
the chest, particularly for detection and determination of chronicity of
hemodynamically significant stenoses and occlusions as well as vascular
anomalies. In addition, stent patency can also be assessed. However, this
technique has a number of limitations that should be recognized to prevent
inappropriate use and misinterpretation.
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Abstract
Introduction
