(Stroke. 1995;26:1753-1758.)
© 1995 American Heart Association, Inc.
Articles |
Preoperative Assessment of the Carotid Bifurcation
Can Magnetic Resonance Angiography and Duplex Ultrasonography Replace Contrast Arteriography?
From the Departments of Radiology (M.R.P., D.K., J.K., R.R.E.) and Surgery (K.C.K., J.J.S.), Beth Israel Hospital, and the Departments of Medicine (K.M.K.), Radiology (R.A.K., J.F.P.), and Surgery (A.D.W.), Brigham and Women's Hospital, Harvard Medical School, Boston, Mass.
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Abstract |
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 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
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Background and Purpose Noninvasive studies are used with increasing frequency to assess the carotid bifurcation before endarterectomy. Therefore, assessment of their diagnostic accuracies is essential for appropriate patient management. We prospectively evaluate two noninvasive tests, magnetic resonance angiography (MRA) and duplex ultrasonography (DU), as potential replacements for contrast arteriography (CA).
Methods A blinded comparison of three-dimensional time-of-flight (TOF) MRA, two-dimensional TOF MRA, and DU in 176 arteries was performed. CA was used as the standard of comparison.
Results Three-dimensional TOF MRA had a sensitivity of 94%, a specificity of 85%, and an accuracy of 88% for the identification of 70% to 99% stenosis; two-dimensional TOF MRA had a sensitivity and specificity that were approximately 10% lower than those of three-dimensional TOF MRA. DU resulted in a sensitivity of 94%, a specificity of 83%, and an accuracy of 86%. Combining data from three-dimensional TOF MRA and DU, allowing for CA only for disparate results, yielded a sensitivity of 100%, a specificity of 91%, and an accuracy of 94% among concordant noninvasive tests, with CA required in 16% of arteries. MRA accurately differentiated 17 carotid occlusions from 16 high-grade (90% to 99%) stenoses, whereas with DU two patent arteries were identified as occluded and one occluded artery was identified as patent.
Conclusions Three-dimensional TOF MRA is the most accurate noninvasive test. Combined use of MRA and DU results in a marked increase in accuracy to a level that obviates the need for CA in a majority of patients.
Key Words: carotid endarterectomy • carotid stenosis • diagnostic imaging • duplex scanning • magnetic resonance imaging
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Introduction |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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CA has generally been proposed as a necessary preoperative study for carotid endarterectomy. However, the cost of CA, as well as the risk of stroke associated with this procedure, has encouraged the development of alternative noninvasive imaging modalities, including MRA and DU, for the detection of significant carotid disease. Accurate evaluation of the carotid bifurcation has become particularly important in view of the NASCET, which confirmed a benefit of carotid endarterectomy in symptomatic patients with 70% to 99% carotid stenosis.1 Similar results were obtained from the MRC European Carotid Surgery Trial, although the method of stenosis measurement differed from that used in the NASCET.2 The more recent multicenter Asymptomatic Carotid Atherosclerosis Study suggests a benefit of carotid endarterectomy in asymptomatic patients with a stenosis greater than 60%.3 As the indications for carotid endarterectomy become increasingly precise, so does the need for accurate and safe assessment of the carotid bifurcation, so that appropriate referral for carotid endarterectomy can be made.
The authors of numerous comparative studies using a variety of noninvasive modalities report varied conclusions.4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Many investigators have assessed the utility of MRA as a screening examination4 5 6 7 8 9 10 11 rather than as a preoperative diagnostic study.12 13 14 15 16 17 18 19 Also, in a majority of these studies, two-dimensional TOF and phase-contrast MRA techniques were used. Both of these latter techniques produce more signal loss at the carotid bifurcation because of dephasing phenomena than do three-dimensional TOF MRA techniques. The previous studies often involved too small a number of patients with disease to address specific subsets of stenosis, ie, the ability of the imaging test to accurately and reliably differentiate between a high-grade stenosis and occlusion. Although MRA and DU have individually been evaluated as potential replacements for CA, the concept of combining the results of these two tests has been suggested but not thoroughly investigated.14 15 16 17 We sought to determine whether concordant three-dimensional TOF MRA and DU results could improve diagnostic accuracy to a level that obviates the need for CA.
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Subjects and Methods |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Over a 19-month period, 88 patients referred for CA because of suspected atherosclerotic disease involving the carotid bifurcation were entered into our study. There were 30 women and 58 men ranging in age from 48 to 87 years (average age, 70 years). Patient risk factors for atherosclerotic disease included hypercholesterolemia (47%), hypertension (73%), diabetes mellitus (35%), and smoking (64%). There were 74 symptomatic carotid bifurcations (42%). Symptoms included transient ischemic attack (24), stroke (21), and amaurosis fugax (29). Carotid endarterectomy was subsequently performed on 86 arteries in 84 patients.
Of these carotid bifurcations, 171 were adequately imaged by CA, 163 by both three-dimensional TOF MRA and CA, 156 by both DU and CA, and 148 by all three modalities. The comparison of two-dimensional TOF MRA and three-dimensional TOF MRA was performed on 87 bifurcations imaged by both techniques. CA images of 5 carotid bifurcations were technically inadequate because of poor vessel opacification resulting from the inability to achieve selective catheterization of the CCA. One minor stroke occurred after CA. Eight bifurcations imaged by MRA were inadequate for evaluation. Reasons for MRA failure included motion (1), failure to image a low-lying bifurcation (1), and marked background signal (6). DU was not performed in 6 patients, and in 1 patient marked calcification obscured the bifurcation. Seventy-one patients had MRA of the circle of Willis.
CA was performed with digital subtraction techniques. MRA of the carotid bifurcation was performed on a 1.5-T Magnetom SP (Siemens Medical Systems) by use of a Helmholtz coil. The multislab three-dimensional transverse acquisition TOF technique used imaging parameters 40/7/1 (TR [repetition time, in milliseconds]/TE [excitation time, in milliseconds]/excitations) at a 20° flip angle, with 52-mm thickness per slab with 62 partitions and 0.812-mm slice thickness.20 The two-dimensional transverse acquisition TOF technique imaging parameters were 31/9/1 (TR/TE/excitations) at a 30° flip angle, with a slab thickness of 124 mm, a 3-mm slice thickness, and a 0.75-mm slice overlap with 55 slices. The three-dimensional TOF MRA of the circle of Willis was performed by use of a circularly polarized head coil with either imaging parameters 29/6/1 (TR/TE/excitations), at a 20° flip angle, or 35/6/1 at a 20° flip angle with magnetization transfer contrast. Two slabs were obtained with 52-mm slab thickness and 64 partitions per slab with 0.812-mm slice thickness. The MRA studies were reviewed after postprocessing with an MIP algorithm, with targeted MIPs used to display projections of each carotid bifurcation separately. The total MRA imaging time was approximately 30 minutes.
MRA and CA images were each reviewed independently by two radiologists;
the MRA reviewers were different from the CA reviewers. For
determination of extracranial stenoses, the CA and MRA studies
were uniformly projected and magnified, and the outline of the
arterial lumen was traced and measured with digital
calipers (Fowler). A percent stenosis was determined in
accordance with the NASCET protocol.1 A signal void was
defined as a discrete discontinuity in the MIP projection. Carotid
occlusion was determined by absence of signal on both two- and
three-dimensional TOF MRA. The values for percent stenosis
for both reviewers were averaged, and the 
statistic was used to
assess interobserver reliability.21 Visual estimates were
used to determine stenoses of the intracranial vessels. CA and
MRA images were also evaluated for the presence, depth, and morphology
of ulceration.
DU was performed either at the Brigham and Women's Hospital (60
carotid bifurcations), the Beth Israel Hospital (80 carotid
bifurcations), or at an outside certified laboratory (16 carotid
bifurcations). PSV and end-diastolic velocity for the
CCA and ICA were measured. We used two criteria to determine the
sensitivity and specificity of DU for predicting a 70% to 99%
stenosis: (1) ICA PSV/CCA PSV >4.022 and (2) ICA
PSV 
2300 mm/s.23
We calculated the sensitivity and specificity for DU, MRA, and their combination for determining various degrees of stenosis, with CA as the standard of comparison. Overall test performance was assessed with ROC analysis.24
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Results |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Assessment of Stenosis by CA
Evaluation of CA revealed 99 carotid bifurcations (58%) with a 0% to 69% stenosis, 37 bifurcations with a 70% to 89% stenosis (22%), 17 bifurcations with a 90% to 99% stenosis (10%), and 18 carotid occlusions (10%). Interobserver reliability between readers was excellent (
=0.93).
Assessment of Stenosis by MRA
Three-dimensional TOF MRA yielded a sensitivity of 94%, a
specificity of 85%, and an accuracy of 88% for the identification of
a 70% to 99% CA stenosis. The interobserver reliability
between readers for three-dimensional TOF MRA was very good
(=0.88). There were 20 carotid bifurcations (12%) for which
three-dimensional TOF MRA and the CA stenosis were
discrepant: 17 false-positive (Fig 1
) and 3
false-negative bifurcations. The mean difference between the degree
of stenoses found by MRA and CA, excluding signal voids, was
5.0±14.3. In 2 false-positive bifurcations, a spurious
stenosis found on MRA appeared to be a result of tortuosity or
kinking of a vessel. There was no obvious explanation for the
discrepancy in the remaining arteries. In 2 of the 3 false-negative
bifurcations, the field imaged by MRA did not include the more severe
stenosis, which in 1 case was in the mid-CCA and in the second
was in the distal ICA. In the third case, artifact from dental fillings
on CA partially obscured the area of stenosis, raising the
possibility that the MRA may have actually been more accurate.
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A signal void was identified by three-dimensional TOF MRA in 28
bifurcations and corresponded to CA stenoses ranging from 40%
to 99% (Fig 2). Four signal voids (confirmed on review
of the source images) were associated with a CA stenosis of
less than 70%. Weak correlation was found between degree of
stenosis and length of signal void (Spearman's rank
correlation of .25).
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In 87 bifurcations both three- and two-dimensional TOF MRAs were
available for comparison. For the identification of a 70% to 99%
stenosis, three-dimensional TOF MRA resulted in a
sensitivity of 92%, a specificity of 83%, and an accuracy of 85%,
whereas the two-dimensional TOF MRA resulted in a sensitivity of
83%, a specificity of 75%, and an accuracy of 77%.
There were 14 bifurcations for which a signal void found by
two-dimensional TOF MRA corresponded to a measurable lumen on
three-dimensional TOF MRA (Fig 3), whereas in 8 bifurcations a
signal void was seen with both techniques. There were no
instances in which an artery with a signal void on
three-dimensional TOF MRA had a measurable lumen on
two-dimensional TOF MRA.
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The sensitivity, specificity, and accuracy of three-dimensional TOF
MRA for depicting a 60% to 99% stenosis were 93%, 83%, and
87%, respectively. Diagnostic accuracies of MRA for four
different levels of CA stenosis are summarized in Table 1. Overall diagnostic performance of
three-dimensional TOF MRA, as defined by the area under the ROC
curve, ranged from .94 for detection of a 60% to 99% stenosis
to .96 for detection of a 50% to 99% stenosis. This value was
.95 for detection of a 70% to 99% stenosis.
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Assessment of Stenosis by DU
With a ratio of ICA/CCA PSV >4.0 used to define a positive test,
the sensitivity, specificity, and accuracy of DU for 70% to 99%
stenosis were 79%, 86%, and 84%, respectively.
Alternatively, with ICA PSV 2300 mm/s used to define a positive test,
these values were 94%, 83%, and 86%, respectively (Table 2). We found the ICA PSV parameter to have
better diagnostic performance than the ICA/CCA PSV
ratio on the basis of the areas under the ROC curves for the ranges of
angiographic stenoses evaluated. Specifically, for detection of
a 70% to 99% stenosis, the areas under the ROC curve were .93
and .90 for ICA PSV and the ICA/CCA PSV ratio, respectively.
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Assessment of Stenosis by Both MRA and DU
We evaluated whether concordant data from three-dimensional
TOF MRA and DU could result in accuracies that are sufficient to
obviate the need for CA. With a ratio of ICA/CCA PSV >4.0, MRA and DU
were concordant in 122 of 148 arteries (82%). For these 122 arteries,
the sensitivity, specificity, and accuracy for a 70% to 99%
stenosis were 97%, 92%, and 93%, respectively.
Twenty-six arteries (18%) with disparate findings on MRA and DU
would have needed to have been imaged by CA (Table 2
). With ICA PSV
2300 mm/s, there was agreement between the noninvasive tests in 124
of 148 arteries (84%). For these 124 arteries, a sensitivity of 100%,
a specificity of 91%, and an accuracy of 94% resulted.
Twenty-four (16%) of these arteries would have required imaging
with CA. Therefore, combining concordant data from both noninvasive
tests markedly increased overall accuracy (94%) compared with
three-dimensional TOF MRA (88%) or DU alone (86%).
Carotid Occlusion
CA identified 16 bifurcations with 90% to 99% stenosis
and 17 occlusions (14 ICA and 3 CCA) in vessels imaged by MRA and CA.
MRA was able to differentiate between high-grade stenoses
and occlusions in all cases. Two occluded arteries were identified as
patent by DU, and one patent ICA was determined to have an occlusion by
DU.
Ulcerations Involving the Carotid Bifurcation
We found multiple examples in which three-dimensional TOF MRA
was not able to depict ulcers that were clearly visible on CA. We
graded ulcerations by quantitating their depth and width. An ulcer was
considered present if the depth was greater than 0.4 mm. There was
tremendous variability between readers' results with regard to the
presence and quantification of ulceration. For the detection of
ulceration, three-dimensional TOF MRA yielded a sensitivity of 22%
compared with CA.
Anatomic Coverage
With the MRA techniques used in this study, the vertical extent of
coverage was limited to 120 mm on the two-dimensional TOF MRA and
70 mm on the three-dimensional TOF MRA. Thus, the entire length of
the extracranial ICA was not visualized. This led to errors in two
cases. In one vessel, a significant lesion in the distal ICA was not
visualized, and in the second artery a lesion in the mid-CCA was not
visualized.
Intracranial Stenoses
Both CA and three-dimensional TOF MRA were used to evaluate
126 arteries for the presence of 50% to 99% stenosis of the
intracranial ICA. There were 11 vessels in which CA indicated a 50% to
99% stenosis of the ICA. There were false-negative results
in 2 arteries (sensitivity, 82%) in which severe occlusive disease in
the more proximal extracranial ICA resulted in marked distal signal
loss with inaccurate depiction of the lesions. There were
false-positive results in 6 vessels (specificity, 95%); all
involved areas in which the ICA was tortuous, such as the carotid
siphon.
Evaluation for branch stenoses involving the anterior, middle,
and posterior cerebral arteries revealed numerous stenoses on
MRA that were either not visualized or much less severe when the same
distribution was appropriately imaged on CA (Fig 4).
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Discussion |
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TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
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Recent studies indicate the appropriateness of carotid endarterectomy for both symptomatic and asymptomatic patients with significant carotid stenoses. For carotid endarterectomy to be of maximal benefit, a low risk of stroke must be associated with the surgical procedure as well as the preoperative imaging study. Although CA has been the traditional preoperative test for carotid endarterectomy, there is a small but definite probability of stroke, ranging from 0.5% to 4%, associated with this procedure.25
Noninvasive imaging modalities including MRA and DU have been proposed as replacements for CA, because both studies have negligible immediate risks. The direct costs of these tests and patient discomfort are also less than those of CA. However, if these tests are not accurate, inappropriate treatment could result.
This study was designed to compare MRA and DU with CA. We felt
information derived from both noninvasive tests could be combined in a
way that would obviate the need for CA when the results of these tests
were in agreement. The sensitivities and specificities that we report
for MRA and DU alone are similar to those in previous
studies.8 13 22 23 Three-dimensional TOF MRA alone
resulted in a sensitivity of 94%, a specificity of 85%, and an
accuracy of 88%. DU alone, with ICA PSV 2300 mm/s used as the
parameter, yielded a sensitivity of 94%, a specificity of
83%, and an accuracy of 86%. For those arteries in which both
noninvasive tests were in agreement, a sensitivity of 100%, a
specificity of 91%, and an accuracy of 94% were achieved. Such an
approach would require that all arteries with discordant MRA and DU
results be imaged by CA. If this strategy were used, CA would have been
necessary for only 16% of the arteries in our series.
Although our group has previously introduced the concept that overall accuracy in the diagnosis of carotid artery stenosis is significantly increased by combining the results of MRA and DU,14 15 Mittl et al9 did not find these tests to be complimentary. However, in their study two-dimensional TOF MRA was used, a technique that we have found to be less accurate than three-dimensional TOF MRA.
Because of our findings, we no longer schedule routine CA in symptomatic patients with carotid stenosis. Rather, we reserve CA for those circumstances in which MRA and DU are not in agreement. Because DU is often used as an initial screening test, the only additional cost is for MRA, which is significantly less expensive than CA.
It is possible that the NASCET and European Carotid Surgery trials will
eventually demonstrate that patients with a stenosis of 50% to
70% may benefit from carotid endarterectomy.
Recent data from the Asymptomatic Carotid
Atherosclerosis Study support performing carotid
endarterectomy in asymptomatic
patients with a stenosis of greater than 60%.3 We
therefore evaluated the ability of MRA to evaluate cutoff points other
than 70%. We found that MRA was consistently accurate in
identifying CA stenoses ranging from 50% to 80% (Table 1).
It has been proposed that the identification and the morphological appearance of ulceration should influence the decision to perform carotid endarterectomy.26 We found MRA to be an extremely poor predictor of ulceration. In recent prospective studies from which current indications for carotid endarterectomy are derived, ulceration alone is not considered a criterion for surgery. Consequently, for most surgeons the insensitivity of MRA to the detection of ulcers does not preclude use of this test in the preoperative management of carotid disease.
Data from our study indicate that MRA has limited ability to accurately image the intracranial circulation. In the evaluation of branch arteries, stenoses were frequently found on MRA that could not be identified or that corresponded to minimal areas of narrowing by CA. We also evaluated the potential for MRA to depict the intracranial ICA. Two patients were identified who had high-grade lesions in the extracranial ICA in tandem with high-grade stenoses of the carotid siphon by CA. In neither patient was the carotid siphon disease depicted by MRA, presumably because of marked signal loss caused by the extracranial lesion. However, despite these two exceptions, MRA was able to assess the intracranial ICA with a sensitivity of 82% and a specificity of 95%. Therefore, MRA can provide useful information about the intracranial circulation with minimal additional cost. In addition, many surgeons will proceed with endarterectomy of an extracranial stenosis despite the existence of a tandem intracranial lesion.27 28 29
A nearly occluded carotid artery may be amenable to carotid endarterectomy, whereas a carotid occlusion, in most instances, is not. We found the combination of two- and three-dimensional TOF MRA to be an excellent means of differentiating between these two conditions. The increased sensitivity of two-dimensional TOF MRA for the slow flow in this situation has been demonstrated.30 The inability to evaluate carotid occlusion continues to be a source of inaccuracy for DU.31 In our series, two occluded carotid arteries were found to be patent by DU. In a third artery, DU predicted an occlusion; however, the artery was found to be patent by CA.
For evaluation of the carotid bifurcation, we have found that the accuracy of three-dimensional TOF MRA is significantly greater than that of two-dimensional TOF MRA. Similar findings have been reported by De Marco et al.12 However, for differentiation between high-grade stenoses and occlusions, two-dimensional TOF MRA provided additional information that was useful in making a final determination. Therefore, we recommend that both studies be routinely obtained in patients referred for evaluation of disease.
We propose the combined use of MRA and DU in the preoperative assessment of carotid bifurcation disease, with CA being used only for those circumstances in which the noninvasive tests are not in agreement. For such an approach to be implemented, MRA and DU need to be of high quality and require state-of-the-art equipment and interpretive expertise. Combining data from both tests can produce an accuracy as high as 94% with no false-negative results. With such a strategy, contrast angiography would be required in only a minority of patients. On the basis of our results, we advocate the combined use of these two noninvasive studies for the preoperative evaluation of patients with carotid artery disease.
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Selected Abbreviations and Acronyms |
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Footnotes |
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Reprint requests to K. Craig Kent, MD, Beth Israel Hospital, 330 Brookline Ave, Boston, MA 02215.
Received June 1, 1995; revision received July 11, 1995; accepted July 11, 1995.
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A.S. Turk, K.M. Johnson, D. Lum, D. Niemann, B. Aagaard-Kienitz, D. Consigny, J. Grinde, P. Turski, V. Haughton, and C. Mistretta Physiologic and Anatomic Assessment of a Canine Carotid Artery Stenosis Model Utilizing Phase Contrast with Vastly Undersampled Isotropic Projection Imaging AJNR Am. J. Neuroradiol., January 1, 2007; 28(1): 111 - 115. [Abstract] [Full Text] [PDF]
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C. W. Yang, J. C. Carr, S. F. Futterer, M. D. Morasch, B. P. Yang, S. M. Shors, and J. P. Finn Contrast-Enhanced MR Angiography of the Carotid and Vertebrobasilar Circulations AJNR Am. J. Neuroradiol., September 1, 2005; 26(8): 2095 - 2101. [Abstract] [Full Text] [PDF]
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M. Berg, Z. Zhang, A. Ikonen, P. Sipola, R. Kalviainen, H. Manninen, and R. Vanninen Multi-Detector Row CT Angiography in the Assessment of Carotid Artery Disease in Symptomatic Patients: Comparison with Rotational Angiography and Digital Subtraction Angiography AJNR Am. J. Neuroradiol., May 1, 2005; 26(5): 1022 - 1034. [Abstract] [Full Text] [PDF]
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J. K. DeMarco, J. Huston III, and M. A. Bernstein Evaluation of Classic 2D Time-of-Flight MR Angiography in the Depiction of Severe Carotid Stenosis Am. J. Roentgenol., September 1, 2004; 183(3): 787 - 793. [Abstract] [Full Text] [PDF]
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C. H. Wierks and N. Labropoulos Noninvasive Carotid Imaging Perspectives in Vascular Surgery and Endovascular Therapy, June 1, 2004; 16(2): 89 - 99. [Abstract] [PDF]
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I. Borisch, M. Horn, B. Butz, N. Zorger, B. Draganski, T. Hoelscher, U. Bogdahn, and J. Link Preoperative Evaluation of Carotid Artery Stenosis: Comparison of Contrast-Enhanced MR Angiography and Duplex Sonography with Digital Subtraction Angiography AJNR Am. J. Neuroradiol., June 1, 2003; 24(6): 1117 - 1122. [Abstract] [Full Text] [PDF]
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M. Cosottini, A. Pingitore, M. Puglioli, M. C. Michelassi, G. Lupi, A. Abbruzzese, R. Calabrese, M. Lombardi, G. Parenti, and C. Bartolozzi Contrast-Enhanced Three-Dimensional Magnetic Resonance Angiography of Atherosclerotic Internal Carotid Stenosis as the Noninvasive Imaging Modality in Revascularization Decision Making Stroke, March 1, 2003; 34(3): 660 - 664. [Abstract] [Full Text] [PDF]
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J. S. Coselli and P. L. Moreno Descending and Thoracoabdominal Aneurysm Card. Surg. Adult, January 1, 2003; 2(2003): 1169 - 1190. [Full Text]
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J. C. Carr, J. Ma, V. Desphande, S. Pereles, G. Laub, and J. P. Finn High-Resolution Breath-Hold Contrast-Enhanced MR Angiography of the Entire Carotid Circulation Am. J. Roentgenol., March 1, 2002; 178(3): 543 - 549. [Abstract] [Full Text] [PDF]
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U. G.R. Schulz and P. M. Rothwell Major Variation in Carotid Bifurcation Anatomy: A Possible Risk Factor for Plaque Development? Stroke, November 1, 2001; 32(11): 2522 - 2529. [Abstract] [Full Text] [PDF]
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D. C.C. Johnston and L. B. Goldstein Clinical carotid endarterectomy decision making: Noninvasive vascular imaging versus angiography Neurology, April 24, 2001; 56(8): 1009 - 1015. [Abstract] [Full Text] [PDF]
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G. Melissano, R. Castellano, R. Zucca, and R. Chiesa Results of Carotid Endarterectomy Performed with Preoperative Duplex Ultrasound Assessment Alone Vascular and Endovascular Surgery, March 1, 2001; 35(2): 95 - 101. [Abstract] [PDF]
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M. Koga, K. Kimura, K. Minematsu, and T. Yamaguchi Diagnosis of Internal Carotid Artery Stenosis Greater than 70% with Power Doppler Duplex Sonography AJNR Am. J. Neuroradiol., February 1, 2001; 22(2): 413 - 417. [Abstract] [Full Text] [PDF]
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G. B. Anderson, R. Ashforth, D. E. Steinke, R. Ferdinandy, and J. M. Findlay CT Angiography for the Detection and Characterization of Carotid Artery Bifurcation Disease Stroke, September 1, 2000; 31(9): 2168 - 2174. [Abstract] [Full Text] [PDF]
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J. M. Serfaty, P. Chirossel, J. M. Chevallier, R. Ecochard, J. C. Froment, and P. C. Douek Accuracy of Three-Dimensional Gadolinium-Enhanced MR Angiography in the Assessment of Extracranial Carotid Artery Disease Am. J. Roentgenol., August 1, 2000; 175(2): 455 - 463. [Abstract] [Full Text] [PDF]
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O. E. H. Elgersma, A. F. J. Wüst, P. C. Buijs, Y. van der Graaf, B. C. Eikelboom, and W. P. T. M. Mali Multidirectional Depiction of Internal Carotid Arterial Stenosis: Three-dimensional Time-of-Flight MR Angiography versus Rotational and Conventional Digital Subtraction Angiography Radiology, August 1, 2000; 216(2): 511 - 516. [Abstract] [Full Text]
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P. M. Rothwell, S. T. Pendlebury, J. Wardlaw, and C. P. Warlow Critical Appraisal of the Design and Reporting of Studies of Imaging and Measurement of Carotid Stenosis Stroke, June 1, 2000; 31(6): 1444 - 1450. [Abstract] [Full Text] [PDF]
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O. E. H. Elgersma, P. C. Buijs, A. F. J. Wüst, Y. van der Graaf, B. C. Eikelboom, and W. P. T. M. Mali Maximum Internal Carotid Arterial Stenosis: Assessment with Rotational Angiography versus Conventional Intraarterial Digital Subtraction Angiography Radiology, December 1, 1999; 213(3): 777 - 783. [Abstract] [Full Text]
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J. H. III, S. B. Fain, S. J. Riederer, A. H. Wilman, M. A. Bernstein, and R. F. Busse Carotid Arteries: Maximizing Arterial to Venous Contrast in Fluoroscopically Triggered Contrast-enhanced MR Angiography with Elliptic Centric View Ordering Radiology, April 1, 1999; 211(1): 265 - 273. [Abstract] [Full Text]
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