Proximal Great Vessels of Aortic Arch: Comparison of Three-dimensional Gadolinium-enhanced MR Angiography and Digital Subtraction Angiography

Vertebral artery foraminal segment doppler sonography to detect vertebral and basilar artery stenosis or occlusion

BACKGROUND AND PURPOSE

The diagnostic value of vertebral artery foraminal segment (V2) ultrasonography remains unclear. This study aimed to estimate the predictive value of V2 Doppler imaging for the detection of vertebrobasilar stenosis or occlusion.

METHODS

Three hundred sixty-four vertebral arteries from 182 patients were investigated. Abnormal Doppler spectra were categorized as high-resistance flow (resistive index ≥0.9), low-resistance flow (resistive index ≤0.5), increased flow velocity (peak systolic velocity ≥137.5 cm/second), or no flow signal. On MR angiography, stenosis and occlusion were defined as >50% narrowing and absent flow signals, respectively. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

Sixty of 364 vertebral arteries (16.5%) had V2 Doppler abnormalities, while 89 vertebrobasilar arteries (24.5%) had a stenosis or occlusion. The Doppler abnormalities predicted any stenosis or occlusion in the vertebrobasilar artery with a sensitivity of 56.2% and specificity of 96.4% (PPV, 83.3%; NPV, 87.2%). The hypoplastic vertebral artery (lumen diameter ≤2.7 mm) was more frequently associated with vertebrobasilar stenosis or occlusion, and with abnormal Doppler spectra (mostly high-resistance flow), even when it was nonstenotic, than the normal-diameter vertebral artery (p < .001, chi-square test).

CONCLUSIONS

The low sensitivity seems to be due to the high prevalence of non-V2 lesions not detected on V2 Doppler imaging, suggesting the necessity for a more extensive sonographic examination beyond V2. However, PPV and NPV ≥80% may suggest its usefulness in clinical practice.

Is MRI equivalent to CT in the guidance of TAVR? A pilot study

OBJECTIVES

To compare a comprehensive cardiovascular magnetic resonance imaging (MRI) protocol with contrast-enhanced computed tomography angiography (CTA) for guidance in transcatheter aortic valve replacement (TAVR) evaluation.

METHODS AND RESULTS

Non-contrast three-dimensional (3D) 'whole heart' MRI imaging for aortic annulus sizing and measurements of coronary ostia heights, contrast-enhanced MRI angiography (MRA) for evaluation of transfemoral routes as well as aortoiliofemoral-CTA were performed in 16 patients referred for evaluation of TAVR. Aortic annulus measurements by MRI and CTA showed a very strong correlation (r=0.956, p<0.0001; effective annulus area for MRI 430±74 vs. 428±78 mm² for CTA, p=0.629). Regarding decision for valve size there was complete consistency between MRI and CTA. Moreover, vessel luminal diameters and angulations of aortoiliofemoral access as measured by MRA and CTA showed overall very strong correlations (r= 0.819 to 0.996, all p<0.001), the agreement of minimal vessel diameter between the two modalities revealed a bias of 0.02 mm (upper and lower limit of agreement: 1.02 mm and -0.98 mm).

CONCLUSIONS

In patients referred for TAVR, MRI measurements of aortic annulus and minimal aortoiliofemoral diameters showed good to excellent agreement. Decisions based on MRI measurements regrading prosthesis sizing and transfemoral access would not have modified TAVR-strategy as compared to a CTA-based choice.

KEY POINTS

• 'Whole heart' MRI and CTA measurements of aortic annulus correlate very strongly. • MRI- and CTA-based prostheses sizing are in excellent agreement. • MRA and CTA equally guide TAVR access strategy.

3D black blood MR angiography of the carotid arteries. A simple sequence for plaque hemorrhage and stenosis evaluation

OBJECTIVES

To evaluate the diagnostic performance of a new three-dimensional T1-weighted turbo-spin-echo sequence (3D T1-w TSE) compared to 3D contrast-enhanced angiography (CE-MRA) for stenosis measurement and compared to 2D T1-w TSE for intra-plaque hemorrhage (IPH) detection.

METHODS

Eighty three patients underwent carotid MRI, using a new elliptic-centric phase encoding T1-weighted 3D TSE sequence in addition to the clinical protocol. Two observers evaluated image quality, presence of flow artifacts, and presence of intra-plaque hemorrhage, and computed the NASCET degree of stenosis for CE-MRA and for the new sequence. Inter-observer agreement and correlation between 3D TSE and CE-MRA for NASCET stenosis was estimated using Cohen's kappa, and correlation using linear regression and Bland-Altman plots. Histology was performed on endarterectomy samples for 18 patients. Sensitivity and specificity of 2D and 3D TSE for IPH diagnosis were computed.

RESULTS

3D TSE showed better image quality than 2D TSE (p<0.05). Interobserver agreement was good (kappa≥0.86). Correlation between 3D TSE and CE-MRA was excellent (R=0.95) for NASCET stenosis. Sensitivity and specificity for IPH diagnosis was 50% and 100% for 2D TSE and 100% and 83% for the 3D TSE.

CONCLUSIONS

The new 3D T1-w TSE allows both reliable measures of carotid stenosis, with a slight overestimation compared to CE-MRA (5%), and improved IPH identification, compared to 2D TSE.

Long-term outcome of vertebral artery origin stenosis in patients with acute ischemic stroke

Background

Vertebral artery origin (VAO) stenosis is occasionally observed in patients who have acute ischemic stroke. We investigated the long-term outcomes and clinical significance of VAO stenosis in patients with acute ischemic stroke.

Methods

We performed a prospective observational study using a single stroke center registry to investigate the risk of recurrent stroke and vascular outcomes in patients with acute ischemic stroke and VAO stenosis. To relate the clinical significance of VAO stenosis to the vascular territory of the index stroke, patients were classified into an asymptomatic VAO stenosis group and a symptomatic VAO stenosis group.

Results

Of the 774 patients who had acute ischemic stroke, 149 (19.3%) of them had more than 50% stenosis of the VAO. During 309 patient-years of follow-up (mean, 2.3 years), there were 7 ischemic strokes, 6 hemorrhagic strokes, and 2 unknown strokes. The annual event rates were 0.97% for posterior circulation ischemic stroke, 4.86% for all stroke, and 6.80% for the composite cardiovascular outcome. The annual event rate for ischemic stroke in the posterior circulation was significantly higher in patients who had symptomatic VAO stenosis than in patients who had asymptomatic stenosis (1.88% vs. 0%, p = 0.046). In a multivariate analysis, the hazard ratio, per one point increase of the Essen Stroke Risk Score (ESRS) for the composite cardiovascular outcome, was 1.46 (95% CI, 1.02-2.08, p = 0.036).

Conclusions

Long-term outcomes of more than 50% stenosis of the VAO in patients with acute ischemic stroke were generally favorable. Additionally, ESRS was a predictor for the composite cardiovascular outcome. Asymptomatic VAO stenosis may not be a specific risk factor for recurrent ischemic stroke in the posterior circulation. However, VAO stenosis may require more clinical attention as a potential source of recurrent stroke when VAO stenosis is observed in patients who have concurrent ischemic stroke in the posterior circulation.

Treatment of vertebral artery origin stenosis with a Pharos stent device: a single center experience

Atherosclerotic stenosis of vertebral artery (VA) origin exceeding 70% severity accounts for one third of all vertebrobasilar strokes. For a period of one year the results of endovascular treatment of VA stenosis with the new Pharos stent device were assessed.Twenty-two patients with symptomatic VA stenosis were treated with the Pharos stent. Clinical status and stenosis grade were documented before treatment and 24 hours, one, three and twelve months after treatment via ultrasound and magnetic resonance tomography.All procedures proved to be technically successful without the occurrence of intra-procedural complications. During the observation period of more than one year, 55% of patients were documented with a mean stenosis degree of 60%: two (10%) of these patients showed a residual stenosis after angioplasty and nine patients (45%) an in-stent restenosis, whereas only two patients were documented with a hemodynamically relevant in-stent restenosis of 80%. These two patients were retreated with balloon dilatation. None of the patients showed neurological deterioration or new abnormalities at magnetic resonance tomography examination. Neither VA occlusion nor restenosis of the contralateral VA negatively affected the clinical outcome. An in-stent restenosis was developed by more female than male patients.VA origin stenting with the Pharos stent device is an effective treatment of stenosis. The good clinical results compared to the high restenosis rates have to be examined in further studies. Pin particular, it has to be determined whether the Pharos stent allows the vessel time for collateralization, whether double antiplatelet treatment prevents recurrent cerebrovascular events or whether merely the low restenosis degree is causative for the clinical outcome.

Magnetic resonance angiography: current status and future directions

With recent improvement in hardware and software techniques, magnetic resonance angiography (MRA) has undergone significant changes in technique and approach. The advent of 3.0 T magnets has allowed reduction in exogenous contrast dose without compromising overall image quality. The use of novel intravascular contrast agents substantially increases the image windows and decreases contrast dose. Additionally, the lower risk and cost in non-contrast enhanced (NCE) MRA has sparked renewed interest in these methods. This article discusses the current state of both contrast-enhanced (CE) and NCE-MRA. New CE-MRA methods take advantage of dose reduction at 3.0 T, novel contrast agents, and parallel imaging methods. The risks of gadolinium-based contrast media, and the NCE-MRA methods of time-of-flight, steady-state free precession, and phase contrast are discussed.

Magnetic resonance angiography of fetal vessels: feasibility study in the sheep fetus

PURPOSE

The aim of this study was to perform fetal magnetic resonance angiography (MRA) in utero in a sheep model.

MATERIAL AND METHODS

Images of the great vessels, the heart, and the tracheal tree were performed on four pregnant ewes with a 1.5-T scanner (Philips Medical Systems, Best, The Netherlands). MRA was achieved in utero using a nontriggered free-breathing three-dimensional balanced fast field echo (FFE) technique. All obtained MRA images were evaluated in consensus on a three-point scale by two radiologists with 9 and 4 years of experience in fetal MRI, respectively.

RESULTS

The fetal heart frequencies were between 130 and 160 bpm. The aorta from the aortic bulb to the bifurcation as well as some of the main aortic branches could be depicted. The pulmonary trunk and arteries, the superior and inferior caval veins, and the subsegmental branches of the trachea could also be visualized.

CONCLUSION

The nontriggered MRA of the fetal great vessels with images of the tracheal tree allowed an excellent evaluation of anatomical structures.

Long-term outcome of symptomatic severe ostial vertebral artery stenosis (OVAS)

INTRODUCTION

The optimal management of patients with symptomatic severe ostial vertebral artery stenosis (OVAS) is currently unclear. We analyzed the long-term outcome of consecutive patients with OVAS who received either medical treatment (MT) or vertebral artery stenting (VAS).

METHODS

Thirty-nine (>70%) patients with severe OVAS were followed for a mean period of 2.8 years. The decision for VAS (n = 10) or MT (n = 29) was left to the clinician. The Kaplan-Meier method was used to assess the risk of recurrent stroke, transient ischemic attack (TIA), or death over the study period.

RESULTS

Patients in the VAS group were significantly younger and more likely to have bilateral VA disease (P = 0.04 and P = 0.02). VAS was successfully performed in all ten patients. The periprocedural risk within 30 days was 10% (one TIA). The overall restenosis rate was 10%. One restenosis occurred after 9 months in a patient treated with bare-metal stent. At 4 years of follow-up, VAS showed a nonsignificant trend toward a lower risk for the combined endpoint of TIA and stroke in posterior circulation compared to medical treatment (10% vs. 45%, P = 0.095; relative risk (RR) = 0.24, 95% confidence interval (CI) 0.031-1.85). Patients with bilateral VA disease had a significantly lower recurrence risk after VAS compared with medical treatment (0% vs. 91% at 4 years, P = 0.004; RR 0.10, 95% CI 0.022-0.49)

CONCLUSION

VAS was performed without permanent complications in this small series of patients with symptomatic severe OVAS. The long-term benefit seems to be confined to patients with bilateral but not to those with unilateral VA disease.

Dual-energy CTA with bone removal for transcranial arteries: intraindividual comparison with standard CTA without bone removal and TOF-MRA

RATIONALE AND OBJECTIVES

Dual-source computed tomography enables bone removal on computed tomographic angiographic data on the basis of simultaneous dual-energy (DE) acquisition. The aim of this study was to evaluate the impact of this technique for the assessment of transcranial arteries. Therefore, the degree of stenosis of the transcranial arteries on DE computed tomographic angiography (CTA) with bone removal was compared to those on standard CTA and time-of-flight (TOF) magnetic resonance angiography (MRA).

MATERIALS AND METHODS

DE-CTA was performed using a dual-source computed tomographic scanner in 50 patients with suspected cerebrovascular disease. From the source images on DE-CTA, data sets with and without bone removal were reconstructed. TOF-MRA was performed on a 1.5-T scanner. Two blinded radiologists evaluated the segments of the internal carotid artery (C2-C7), the vertebral artery (V4), and the basilar artery for degree of stenosis. A five-step scale (0%-49%, 50%-69%, 70%-89%, 90%-99%, and 100% [occlusion]) for degree of stenosis was applied. Wilcoxon's signed-rank test was used for statistical analysis.

RESULTS

The degrees of stenosis on standard CTA were consistent with those on TOF-MRA in all segments. In contrast, DE-CTA showed significantly higher degrees of stenosis compared to standard CTA and TOF-MRA in both C2 segments (P < .001). In addition, DE-CTA revealed a significantly higher degree of stenosis compared to standard CTA and TOF-MRA in the left C4 segment (P < .01 and P < .005, respectively). All other segments showed no significant differences of stenosis among TOF-MRA, DE-CTA, and standard CTA.

CONCLUSIONS

Compared to TOF-MRA, standard CTA showed similar results. In contrast, DE-CTA revealed significant overestimation of stenosis for segments with close relations to bony structures as well as in calcified stenosis. Consequently, such findings on DE-CTA require confirmation with standard CTA or MRA to eliminate false-positive results.

Assessment of cerebral arteriovenous malformations with high temporal and spatial resolution contrast-enhanced magnetic resonance angiography: a review from protocol to clinical application

The combination of high spatial and high temporal resolution contrast-enhanced magnetic resonance angiography (MRA) at 3.0 T has enabled the detailed evaluation of functional vascular anatomy and hemodynamics of cerebral arteriovenous malformations (AVMs). Key contributory technical factors for the successful implementation of MRA in patients with different vascular pathologies are multicoil and multichannel receiver arrays, which enable higher parallel acquisition at 3.0 T over a uniform and a large field of view for highly temporally and spatially resolved MRA. Magnetic resonance angiography enables both screening of patients with suspected AVMs and follow-up of patients after therapy. It allows the characterization of AVMs with respect to nidus configuration, size, venous drainage, and so on, according to the Spetzler-Martin classification.

Supraaortic arteries: contrast material dose reduction at 3.0-T high-spatial-resolution MR angiography--feasibility study

PURPOSE

To evaluate and compare the diagnostic image quality resulting from three contrast agent dose regimens for 3.0-T high-spatial-resolution three-dimensional magnetic resonance (MR) angiography of the supraaortic arteries.

MATERIALS AND METHODS

Institutional review board approval was obtained; informed consent was waived for this HIPAA-compliant study. One hundred twenty consecutive patients who underwent 3.0-T three-dimensional high-spatial-resolution contrast material-enhanced MR angiography of the supraaortic arteries with an identical acquisition protocol were assigned to either the high-dose (0.154 mmol per kilogram of body weight), intermediate-dose (0.097 mmol/kg), or low-dose (0.047 mmol/kg) group. Two readers evaluated resulting images for arterial definition, venous contamination, and arterial stenosis. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were evaluated at six consistent sites. Statistical analysis was performed with the Kruskal-Wallis, Wilcoxon signed rank, and analysis of variance tests and the kappa coefficient.

RESULTS

Readers 1 and 2 scored vascular definition as excellent or sufficient for diagnosis in 1311 of 1360 segments and in 1313 of 1360 segments in the high-dose group (kappa = 0.73), in 1321 of 1354 and in 1319 of 1354 segments in the intermediate-dose group (kappa = 0.77), and in 1322 of 1350 and in 1320 of 1350 segments in the low-dose group (kappa= 0.66), respectively. Arterial occlusive disease was detected by reader 1 in 52, 27, and 98 segments in the high-, intermediate-, and low-dose groups, respectively. Arterial occlusive disease was detected by reader 2 in 48, 25, and 100 segments in high-, intermediate-, and low-dose groups, respectively. No significant difference existed among the three groups regarding arterial definition scores (reader 1, P = .21; reader 2, P = .25) and venous contamination scores (reader 1, P = .38; reader 2, P = .35). SNRs and CNRs were lower in the low-dose group (P < .01).

CONCLUSION

At 3.0 T, high-spatial-resolution MR angiography of the supraaortic arteries can be performed with contrast agent doses as low as 0.047 mmol/kg, without compromising image quality, acquisition speed, or spatial resolution.

SUPPLEMENTAL MATERIAL

http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC1http://radiology.rsnajnls.org/cgi/content/full/249/3/980/DC2.

Qualitative and quantitative analysis of routinely postprocessed (CLEAR) CE-MRA data sets: are SNR and CNR calculations reliable?

RATIONALE AND OBJECTIVES

To evaluate objective image quality parameters for contrast-enhanced magnetic resonance angiography (CE-MRA), contrast-to-noise (CNR), and signal-to-noise ratio (SNR) calculations based on signal intensity (SI) and standard deviation (SD) measurements of the vessel, the surrounding tissue (eg, muscle), and the background noise outside the body are commonly used. However, modern magnetic resonance scanners often use dedicated software algorithms such as Constant LEvel AppeaRance (CLEAR) to improve image quality, which may affect the established methods of SNR and CNR calculation. The purpose of this study was to intraindividually evaluate the feasibility of conventional techniques used for SNR and CNR calculation of MRA data sets that have been reconstructed with both, a standard (non-CLEAR) and a CLEAR algorithm.

METHODS

Supra-aortic high-resolution CE-MRA of 11 patients with headache symptoms was performed at 1.5 T using reconstruction algorithms generating both, non-CLEAR and CLEAR-corrected images from the acquired data set. A qualitative analysis with regard to image quality and contrast level was performed by two radiologists applying a score system. For quantitative analysis, distribution of SI values was measured in regions of interest in the common carotid artery (CCA) and the C1 segment of the internal carotid artery in identical positions of both data sets for intraindividual comparison of SNR and CNR calculations. For that purpose, three different equations were used for background noise assessment by determining the SD of SIs measured in the air outside the body (Eq. A), the soft tissue adjacent to the analyzed vessel segment (Eq. B), and in a contrast-medium filled tube (reference standard), which was placed around the patient's neck (Eq. C).

RESULTS

The qualitative analysis documented an improved image quality and a higher contrast level for CLEAR-based data sets. SNR and CNR calculations of the CCA and the C1 segment were significantly different for both reconstruction algorithms when using the background noise outside the body for image noise assessment (P<.05 [CCA]; P<.05 [C1]). SNR and CNR calculations based on the soft tissue adjacent to the analyzed segment or a reference standard were comparable.

CONCLUSIONS

For comparative analysis of CE-MRA data sets, SNR and CNR calculations based on SD determination of the background noise signal measured outside the body are not applicable for CE-MRA data sets reconstructed with a CLEAR-based algorithm. Therefore, noise should rather be assessed in the perivascular tissue to enable proper comparative analysis of CLEAR-enhanced CE-MRA data sets.

Radiological reasoning: extracranial causes of unilateral decreased brain perfusion

OBJECTIVE

A 50-year-old man presented with neurologic symptoms and upper extremity claudication associated with exercise. Perfusion MRI of the brain showed delayed time-to-peak in the right cerebral hemisphere, and MR angiography (MRA) of the circle of Willis showed decreased flow-related enhancement in the right internal carotid artery and its branches. Neck MRA showed occlusion of the right innominate (brachiocephalic) artery and retrograde flow in the ipsilateral vertebral artery. On the basis of this clinical scenario, we discuss the radiologic evaluation of unilateral decreased brain perfusion, which, in this case, was due to an occlusion of the innominate artery with resultant innominate steal.

CONCLUSION

In the absence of an explanatory intracranial stenosis, the finding of unilateral decreased cerebral perfusion on MRI or CT mandates evaluation of the aortic arch and cervical arteries to determine a level and cause of occlusion. Severe stenoses may be associated with steal phenomena, which can be diagnosed with MRA or Doppler sonography.

MR angiography at 3 T for assessment of the external carotid artery system

OBJECTIVE

A number of clinical situations exist in which high-resolution depiction of the external carotid artery system is required, a task not previously addressed by MR angiography. The purpose of this study was to evaluate the extent to which high-spatial-resolution MR angiography at 3 T can be used to map the normal external carotid artery system.

SUBJECTS AND METHODS

Twenty-three consenting adult patients were prospectively evaluated. Images acquired were evaluated by two independent observers, and each branch vessel was scored with regard to image quality, presence and grade of stenoses, and artifacts. Interobserver agreement regarding image quality and the presence and degree of stenosis was tested using the kappa coefficient. Differences in quality ratings between the two observers were assessed using the paired Student's t test.

RESULTS

Of 828 vessels analyzed, 92.63% were designated of diagnostic quality with no significant difference between the observers' image quality scores (p = 0.63). Good agreement was determined regarding image quality achieved (kappa = 0.716). All examinations were free of artifact sufficient to interfere with confident interpretation. Excellent correlation was seen with regard to stenosis detection and grading (kappa = 0.857). Of the external carotid artery systems assessed, 82.6% showed conventional anatomic vascular branching.

CONCLUSION

High-spatial-resolution, 3D contrast-enhanced MR angiography at 3 T using sagittal source data acquisition and an advanced acceleration factor of 6 allows high-quality (92.63% of arterial segments) visualization of the external carotid artery system, with complete head and neck vascular coverage.

Imaging of vertebral artery stenosis: a systematic review

BACKGROUND AND PURPOSE

Posterior circulation stroke accounts for 20% of ischaemic strokes. Recent data suggest that the early stroke recurrence risk is high and comparable with carotid artery disease. Vertebral artery stenosis accounts for approximately 20% of posterior circulation stroke, and with endovascular treatment available accurate diagnostic imaging is important. We performed a systematic literature review to validate the accuracy of the non-invasive imaging techniques Duplex ultrasound (DUS), magnetic resonance angiography (MRA) and computed tomographic angiography (CTA) in detecting severe vertebral artery stenosis, with intra-arterial angiography (IAA) as the reference standard.

METHODS

We identified studies that used non-invasive imaging and IAA as the reference standard to determine vertebral artery stenosis and provided adequate data to calculate sensitivity and specificity. We analysed the quality of these studies, looked for evidence of heterogeneity and performed subgroup analysis for different degrees of stenosis.

RESULTS

11 studies categorised stenosis into 50-99%. The sensitivity of CTA (single study) and pooled sensitivities of contrast enhanced MRA (CE-MRA) and colour duplex were 100% (95% CI 15.8 to 100), 93.9% (79.8 to 99.3) and 70.2% (54.2 to 83.3), respectively. The specificities for CTA, CE-MRA and colour duplex were 95.2% (83.8 to 99.4), 94.8% (91.1 to 97.3) and 97.7% (95.2 to 99.1). However, specificities for CE-MRA and colour duplex demonstrated significant heterogeneity (p = 0.003 and p = 0.002, respectively).

CONCLUSIONS

CE-MRA and possibly CTA may be more sensitive in diagnosing vertebral artery stenosis than DUS. However, data are limited and further high quality studies comparing DUS, MRA and CTA with IAA are required.

First-Pass Whole-Body Magnetic Resonance Angiography (MRA) Using the Blood-Pool Contrast Medium Gadofosveset Trisodium

OBJECTIVES

To evaluate gadofosveset trisodium for first-pass magnetic resonance angiography (MRA) in the setting of whole-body MRA (WB-MRA).

MATERIALS AND METHODS

Forty patients were examined using either 10 mL gadofosveset trisodium (n = 20) or 30 mL gadopentetate dimeglumine (n = 20), followed by arterial-phase imaging of 4 consecutive anatomic regions. Signal intensity was measured in 2 vessels per region. Relative contrast values (RC) were calculated. Arterial contrast, venous overlay, and image quality were rated by 2 radiologists. The Mann-Whitney U test was used to test for significance.

RESULTS

Compared with gadopentetate dimeglumine, gadofosveset trisodium enhanced imaging revealed higher RC values in 2 vessel regions, with the differences being significant in 3 of 4 vessel segments. Gadofosveset trisodium revealed lower RC values in 2 regions with significant differences in 2 segments. Qualitative evaluation revealed higher ratings for gadofosveset trisodium regarding all 3 criteria with significant differences in 2 regions.

CONCLUSIONS

Gadofosveset trisodium serves well for first-pass imaging in WB-MRA.

Supraaortic arteries: contrast-enhanced MR angiography at 3.0 T--highly accelerated parallel acquisition for improved spatial resolution over an extended field of view

PURPOSE

To prospectively use 3.0-T breath-hold high-spatial-resolution contrast material-enhanced magnetic resonance (MR) angiography with highly accelerated parallel acquisition to image the supraaortic arteries of patients suspected of having arterial occlusive disease.

MATERIALS AND METHODS

Institutional review board approval and written informed consent were obtained for this HIPAA-compliant study. Eighty patients (44 men, 36 women; age range, 44-90 years) underwent contrast-enhanced MR angiography of the head and neck at 3.0 T with an eight-channel neurovascular array coil. By applying a generalized autocalibrating partially parallel acquisition algorithm with an acceleration factor of four, high-spatial-resolution (0.7 x 0.7 x 0.9 mm = 0.44-mm(3) voxels) three-dimensional contrast-enhanced MR angiography was performed during a 20-second breath hold. Two neuroradiologists evaluated vascular image quality and arterial stenoses. Interobserver variability was tested with the kappa coefficient. Quantitation of stenosis at MR angiography was compared with that at digital subtraction angiography (DSA) (n = 13) and computed tomographic (CT) angiography (n = 12) with Spearman rank correlation coefficient (R(s)).

RESULTS

Arterial stenoses were detected with contrast-enhanced MR angiography in 208 (reader 1) and 218 (reader 2) segments, with excellent interobserver agreement (kappa = 0.80). There was a significant correlation between contrast-enhanced MR angiography and CT angiography (R(s) = 0.95, reader 1; R(s) = 0.87, reader 2) and between contrast-enhanced MR angiography and DSA (R(s) = 0.94, reader 1; R(s) = 0.92, reader 2) for the degree of stenosis. Sensitivity and specificity of contrast-enhanced MR angiography for detection of arterial stenoses greater than 50% were 94% and 98% for reader 1 and 100% and 98% for reader 2, with DSA as the standard of reference. Vascular image quality was sufficient for diagnosis or excellent for 97% of arterial segments evaluated.

CONCLUSION

By using highly accelerated parallel acquisition, the described 3.0-T contrast-enhanced MR angiographic protocol enabled visualization and characterization of the majority of supraaortic arteries, with diagnostic or excellent image quality (97% of arterial segments) and diagnostic values comparable with those obtained by using CT angiography and DSA for detection of arterial stenoses.

Practical noninvasive neurovascular imaging of the neck arteries in patients with stroke, transient ischemic attack, and suspected arterial disease that may lead to ischemia, infarction, or flow abnormalities

Stroke is the third leading cause of death in the United States, killing nearly 157,000 people a year with an estimated society cost of dollar 58 billion in 2006. A large percentage of ischemic strokes is secondary to extracranial carotid and vertebral arterial disease. While digital subtraction angiography has traditionally been used for the initial evaluation of the degree of stenosis, noninvasive imaging has moved to the forefront in the extracranial arterial evaluation. The importance of understanding the imaging techniques, findings, interpretation, artifacts, and pitfalls is essential to appropriate patient management.

High spatial-resolution CE-MRA of the carotid circulation with parallel imaging: comparison of image quality between 2 different acceleration factors at 3.0 Tesla

PURPOSE

We sought to evaluate and compare the image quality and vessel delineation of the carotid arteries with high spatial-resolution contrast-enhanced MRA (CE-MRA) at 3.0 T using integrated parallel acquisition (iPAT) with acceleration factors of 2 and 4.

MATERIALS AND METHODS

Using an 8-channel neurovascular array coil, we performed prospective high-spatial resolution CE-MRA at 3.0 T of the head and neck on 24 patients (11 men, 13 women, ages 37-89) with suspected arterio-occlusive disease who were assigned randomly to 2 groups. Twelve patients (group A) were examined with a 3D-GRE sequence using iPAT with acceleration factor of 2. For the next 12 patients (group B) a near-identical sequence with an acceleration factor of 4 was applied. Higher iPAT factors were used to increase the spatial-resolution while keeping scan time unchanged. Two volunteers were scanned by both protocols. Phantom measurements were performed to assess the signal-to-noise ratio (SNR). The presence of artifact, noise, image quality of the arterial segments, and the presence and degree of arterial stenosis were evaluated independently by 2 radiologists. Statistical analysis of data was performed by using Wilcoxon rank sum test and 2-sample Student t test (P < 0.05 was indicative a statistically significant difference). The interobserver variability was tested by kappa coefficient.

RESULTS

SNR values were significantly lower when iPAT with acceleration factor of 4 was used (P < 0.001). There was no significant difference between 2 groups in regards to image noise (P = 0.67) and artifact (P = 0.8). Both readers visualized the majority of carotid circulation with good image quality in both groups. For smaller intracranial arteries, such as the second-division of anterior and middle cerebral artery, anterior communicating artery, and superior cerebellar artery, the image quality and vessel delineation was significantly better at an iPAT factor of 4 (P < 0.01). The overall interobserver agreement for both the vessel depiction, and detection of arterial stenoses was higher in group B compared with group A.

CONCLUSION

Use of parallel acquisition techniques with a high acceleration factor (iPAT-4) results in superior depiction of small intracranial arterial segments. Imaging at higher magnetic field strength, in addition to the use of an optimized 8-channel array coil, provides sufficient SNR to support faster parallel acquisition protocols, leading to improved spatial-resolution. More extensive clinical studies are warranted to establish the range of applications and confirm the accuracy of the technique.

Innominate Artery Occlusive Disease: Sonographic Findings

OBJECTIVE

The objective of this study was to report the sonographic abnormalities in a group of patients with angiographically proven innominate artery stenosis and occlusion.

MATERIALS AND METHODS

A review of all cerebrovascular sonograms at our institutions was undertaken to identify patients with complete or partial flow reversal in the right vertebral artery and reversal or midsystolic deceleration of flow in any one of the three major segments of the right carotid system (common, internal, or external carotid artery). The distribution and appearance of these abnormalities was evaluated, and the presence or absence of tardus-parvus waveforms was noted in any segment of the right carotid artery. Additionally, a left to right common carotid peak systolic velocity ratio (LCCA/RCCA) was calculated and compared to published normal values. All patients had correlative contrast or MR angiography. Correlation was made between the severity of stenosis as determined by angiographic images and waveform aberrations as well as the more objective LCCA/RCCA ratios.

RESULTS

Twelve patients were identified as having the abnormalities described above in the right vertebral and carotid arteries. Doppler waveforms from the right vertebral artery revealed that eight of the 12 patients had complete reversal of flow at rest. Bidirectional flow was found in the remaining four as manifested by the presence of marked midsystolic deceleration. In the carotid arteries, one patient had complete reversal of flow in all segments of the right carotid system. Waveforms with midsystolic deceleration were identified in at least one of the carotid arteries of the remaining 11 patients: common carotid artery (8/11 = 73%), internal carotid artery (10/11 = 91%), external carotid artery (3/11 = 27%). The average LCCA/RCCA was 3.1 with a range of 1.7 to 5.7 (normal = 0.7-1.3). All patients had severe innominate artery disease (from 70% to occlusion) by contrast angiography or MR angiography. There was no correlation between the angiographically determined degree of stenosis and the Doppler findings.

CONCLUSION

A distinctive pattern of hemodynamic alterations occurs in the right vertebral and carotid arteries of patients with severe innominate artery disease. Findings include reversed or bidirectional flow in the right vertebral artery, the presence of midsystolic deceleration in any of the branches of the right carotid system, and elevated LCCA/RCCA ratio.

Safety of Arch Aortography for Assessment of Carotid Arteries

PURPOSE

To retrospectively review the safety of arch aortography and compare complication rates with published figures for selective catheter angiography.

METHODS

The medical records of patients undergoing arch aortography over the last 3 years (n=311; 180 male, 131 female; mean+/-SD age 71.0+/-9.2 years, range 42-90 years) were retrospectively reviewed. Any peri-procedural (0-48 h) complications were recorded. A certified neurologist (MSR/GSV) classified all questionable neurological events.

RESULTS

There were no focal neurological events or deaths (n=0; 0%; CI: 0-0.96%). Non-focal neurological events included mild disorientation (n=2; 0.6%; CI: 0.176-2.31) and unequal pupils (n=1; 0.3%; CI: 0.056-1.79%). Cardiovascular events included symptomatic hypotension (n=4; 1.3%; CI: 0.50-3.25%), angina (n=1; 0.3%; CI: 0.056-1.79%) and arrhythmia (n=4; 1.3%; CI: 0.50-3.25). There were 27 minor access site complications (8.7%; CI: 6.0-12.3). None of these complications extended hospital stay. None of the arch angiograms had to be followed by selective carotid angiography.

CONCLUSION

Arch aortography appears to have a lower neurological complication rate than selective carotid angiography.

Gadolinium-Enhanced Versus Time-of-Flight Magnetic Resonance Angiography: What Is the Benefit of Contrast Enhancement in Evaluating Carotid Stenosis?

Accurate patient selection based on preoperative imaging is imperative to good risk reduction in patients undergoing carotid endarterectomy (CEA). The goal of this study was to assess the accuracy of gadolinium-enhanced magnetic resonance angiography (GE MRA) versus time-of-flight (TOF) MRA in the work-up of patients undergoing CEA. Patients undergoing CEA between 1999 and 2001 were identified from a prospectively maintained institutional database. GE or TOF MRA was obtained on extracranial carotid arteries (n = 319) in patients undergoing CEA. Stenosis on MRA images was graded as moderate (n = 76) or severe (n = 243) by an attending radiologist who was blind to duplex results. Duplex imaging was performed in an Intersocietal Commission for the Accreditation of Vascular Labs (ICAVL) accredited lab, and stenosis was stratified as moderate (50-79%, n = 76) or high (80-99%, n = 243) grade using University of Washington criteria. For each patient, the degree of stenosis as determined by MRA (GE versus TOF) was compared to percent stenosis on duplex. For moderate-grade lesions, GE MRA concurred with duplex in 11.1% (4/36), underestimated in 2.8% (1/36), and overestimated in 86.1% (31/36) of carotid arteries imaged. TOF MRA concurred with duplex in 35% (14/40), underestimated in 0% (0/40), and overestimated in 65% (26/40) of carotid arteries. High-grade lesions demonstrated improved concordance between MRA and duplex. For these lesions, GE MRA concurred with duplex in 95.6% (130/136) of carotid arteries imaged, never overestimated stenosis (0/136), and underestimated in 4.4% (6/136). TOF MRA concurred with duplex 96.3% (103/107), overestimated stenosis as an occlusion in 0.9% (1/107), and underestimated in 2.8% (3/107). In addition to neck visualization, the GE technique allowed simultaneous aortic arch imaging. This was accomplished in 79.1% (136/172) of all GE MRAs. Simultaneous aortic arch imaging was not technically feasible with TOF MRA. For moderate-grade lesions, both MR techniques are inaccurate predictors of degree of carotid stenosis and result in a significant overestimation of stenosis. Each technique demonstrates improved concordance with duplex ultrasound in the setting of severe carotid artery stenoses. The ability of GE MRA to simultaneously image the aortic arch and the neck may allow for detection of occult tandem lesions and other anatomic variations, which may be particularly important in preoperative planning for carotid artery stenting.

Contrast-Enhanced MR Angiography of Subclavian Steal Syndrome: Value of the 2D Time-of-Flight “Localizer” Sign

OBJECTIVE

Our objective was to determine if direction of flow within the vertebral artery could be reliably determined by evaluation of flow-sensitive, low-resolution 2D time-of-flight (TOF) localizer images taken before 3D contrast-enhanced MR angiography (3D CEMRA) sequences in patients with unsuspected subclavian steal syndrome.

CONCLUSION

Vertebral artery patency on 3D CEMRA in cases in which the vessel is absent on the TOF localizer in association with ipsilateral subclavian artery stenosis indicates reversal of flow in the vertebral artery and confirms the subclavian steal phenomenon. The combination of anatomic imaging with 3D CEMRA with functional information provided by the low-resolution TOF localizer confirms the diagnosis of subclavian steal without additional imaging.

Whole-body MR angiography using a novel 32-receiving-channel MR system with surface coil technology: first clinical experience

PURPOSE

To demonstrate the feasibility of detecting atherosclerotic vascular disease using an innovative magnetic resonance angiography (MRA) protocol in combination with a dedicated whole-body MR scanner with new surface coil technology.

MATERIALS AND METHODS

A total of 10 volunteers and eight patients with peripheral arterial occlusive disease (PAOD) were examined at 1.5 T. Conventional digital subtraction angiography (DSA) of the symptomatic region was available as a reference standard in all eight patients. Depending on subjects' size, four to five three-dimensional data sets were acquired using an adapted injection protocol. Images were assessed independently by two readers for vascular pathology. Additionally, signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were measured.

RESULTS

Whole-body MRA yielded excellent sensitivity and specificity of more than 95% for both readers with high interobserver agreement (k = 0.93). Surface coil signal reception rendered a high SNR (mean 151.28 +/- 54.04) and CNR (mean 120.75 +/- 46.47). Despite lower SNR and CNR of the cranial and cervical vessels, a two-step injection protocol exhibited less venous superposition and therefore proved to be superior compared to single-bolus injection.

CONCLUSION

Our approach provides accurate noninvasive high-resolution imaging of systemic atherosclerotic disease, covering the arterial vasculature from intracranial arteries to distal runoff vessels. The recently introduced MR scanner and coil technology is feasible to significantly increase the performance of whole-body MRA.

[Rare cause of pectangina after coronary artery surgery]

The coronary subclavian-steal-syndrome is a rare cause for angina pectoris following A. mammaria interna bypass operation. A 72-year-old male patient presented with vertigo and angina pectoris. A three vessel coronary artery disease was known and coronary artery surgery with three aortocoronary bypasses had been performed a year prior to presentation. A difference in peripheral arterial pressure between the right (150/80 mmHg) and the left (125/75 mmHg) arm was noted at physical examination. Color Doppler sonography of the left vertebral arteria exhibited a retrograde flow suggesting a coronary subclavian-steal-syndrome. Angiography revealed a significant stenosis of the left arteria subclavia. The stenosis was successfully treated with percutaneous transluminal angioplasty and stent implantation.

Subclavian Steal Syndrome: Diagnosis with Perfusion Metrics from Contrast-enhanced MR Angiographic Bolus-timing Examination—Initial Experience

PURPOSE

To retrospectively determine whether differential temporal changes in signal intensity of the vertebral arteries, measured at a bolus-timing examination with a test dose of a gadolinium-based contrast agent, are present in patients with subclavian steal syndrome.

MATERIALS AND METHODS

Institutional review board exemption was obtained, and informed consent was not required for this retrospective study. The study complied with the Health Insurance Portability and Accountability Act. Twenty-five patients with known or clinically suspected atherosclerotic disease of the aortic arch and branch vessels underwent breath-hold contrast material-enhanced magnetic resonance (MR) angiography with circulation time derived from a timing examination by using a test bolus of a gadolinium-based contrast agent. Eight patients (three men and five women aged 54-80 years; mean, 70 years) had subclavian stenosis or occlusion with retrograde vertebral artery flow confirmed with time-of-flight MR angiography, nine patients (eight men and one woman aged 31-91 years; mean, 70 years) had mild to severe ostial stenosis of a single vertebral artery, and eight patients (including four men and four women aged 53-86 years; mean, 73 years) had normal vertebral arteries. The difference in time to peak signal intensity between the right and left vertebral arteries was compared among the three groups by using Fisher exact and Cochran-Mantel-Haenszel tests.

RESULTS

The delay in peak enhancement in the ipsilateral vertebral artery ranged from 2 to 4 seconds (mean, 2.5 seconds) in all eight patients with subclavian steal syndrome. In eight of nine patients with ostial vertebral artery stenosis and eight controls, both vertebral arteries filled simultaneously. The presence of unilateral delayed vertebral artery enhancement was significantly associated with retrograde flow in patients with subclavian steal syndrome, compared with patients with normal flow (P < .01) and those with ostial vertebral artery stenosis (P < .01).

CONCLUSION

A bolus-timing examination performed with a test bolus of the gadolinium-based contrast agent via the neck vessels that demonstrates at least a 2-second delay in peak contrast enhancement in the right or left vertebral arteries may, in the appropriate clinical setting, indicate subclavian steal syndrome.

Imaging the vertebral artery

Although conventional intraarterial digital subtraction angiography remains the gold standard method for imaging the vertebral artery, noninvasive modalities such as ultrasound, multislice computed tomographic angiography and magnetic resonance angiography are constantly improving and are playing an increasingly important role in diagnosing vertebral artery pathology in clinical practice. This paper reviews the current state of vertebral artery imaging from an evidence-based perspective. Normal anatomy, normal variants and a number of pathological entities such as vertebral atherosclerosis, arterial dissection, arteriovenous fistula, subclavian steal syndrome and vertebrobasilar dolichoectasia are discussed.

Ischemic stroke: carotid and vertebral artery disease

Ischemic strokes may have distinct aetiologies, including several different intrinsic arterial pathological disorders. The diagnosis and understanding of these arterial diseases is critical for the correct management of stroke as different treatment approaches are undertaken according to the aetiology. Atherosclerosis is by far the most common arterial disease among adults, and other pathological processes include arterial dissection, small vessel disease, inflammatory and non-inflammatory vasculopathy and vasomotor disorders. In children, there are several vasculopathies responsible for vaso-occlusive disease such as sickle-cell anemia, acute regressive angiopathy and Moya-Moya disease, neurofibromatosis, dissections, vasculitis associated with intracranial and systemic infections. An overview of the major carotid and vertebral pathological diseases responsible for ischemic stroke in adults and children, highlighting the accuracy of the different imaging modalities for its diagnosis and the imaging appearance of these diseases, is given.

Three-dimensional color-coded duplex sonography for assessment of the vertebral artery origin and vertebral artery stenoses

OBJECTIVE

The aim of the study was to assess the potential of 3-dimensional (3D) color-coded duplex sonography (CDS) for evaluation of the vertebral artery origin and stenoses in this location.

METHODS

To compare 2-dimensional (2D) and 3D CDS, both techniques were performed in 25 healthy volunteers and in 18 patients with 21 stenoses of the vertebral artery origin. Stenoses were graded in line with hemodynamic criteria on 2D CDS and according to North American Symptomatic Carotid Endarterectomy Trial criteria on 3D CDS. In 6 patients, digital subtraction angiography (DSA) was performed additionally. Stenoses were graded according to North American Symptomatic Carotid Endarterectomy Trial criteria and compared with 2D and 3D sonographic data.

RESULTS

Overall correlation of both sonographic techniques concerning the grading of the stenoses was good (r = 0.69; P < .01). The interobserver correlation for assessment of stenoses by means of 3D CDS was high (r = 0.94; P < .01). Three-dimensional CDS correlated excellently with DSA in 3 of 6 patients but showed only intermediate or no correlation in the remaining 3 patients. In contrast, spatial information on the stenotic morphologic characteristics was always very comparable with the results obtained by DSA.

CONCLUSIONS

Three-dimensional CDS represents a valuable tool for assessment of the origin of the vertebral artery, allowing important morphologic information on stenoses in this location. For grading of stenoses of the vertebral artery origin, 3D information should be combined with hemodynamic criteria obtained by spectral Doppler imaging in 2D CDS. Three-dimensional CDS could be a valuable tool before interventional procedures of the proximal vertebral artery, saving time and avoiding iodinated contrast agents.