Carotid artery stenosis: intraindividual correlations of 3D time-of-flight MR angiography, contrast-enhanced MR angiography, conventional DSA, and rotational angiography for detection and grading

PURPOSE: To compare three-dimensional (3D) time-of-flight (TOF) MR angiography, contrast-enhanced MR angiography, digital subtraction angiography (DSA), and rotational angiography for depiction of stenosis. MATERIALS AND METHODS: The study had Ethics Committee approval, and each patient gave written informed consent. Forty-nine patients (18 women, mean age, 67.2 years +/- 9.1 [+/- standard deviation], and 31 men, mean age, 63.1 years +/- 8.0) with symptomatic stenosis of internal carotid artery (ICA) diagnosed at duplex ultrasonography underwent transverse 3D TOF MR angiography with sliding interleaved kY acquisition and coronal contrast-enhanced MR angiography, followed by DSA and rotational angiography within 48 hours. MR angiography was performed at 1.5-T with a cervical coil. Contrast-enhanced MR angiograms were obtained after a bolus injection of 20 mL of gadobenate dimeglumine. Maximum ICA stenosis on maximum intensity projection and source images was quantified according to NASCET criteria. Correlations for 3D TOF MR angiography, contrast-enhanced MR angiography, DSA, and rotational angiography were determined by means of cross tabulation, and accuracy for detection and grading of stenoses were calculated. Data were evaluated with analysis of variance, Wilcoxon signed rank test, and McNemar test, all at significance of P < .05. RESULTS: Ninety-eight ICAs were evaluated at contrast-enhanced MR angiography, DSA, and rotational angiography, and 97 were evaluated at 3D TOF MR angiography. Correlations for contrast-enhanced MR angiography, 3D TOF MR angiography, and DSA relative to rotational angiography were r2 = 0.9332, r2 = 0.9048, and r2 = 0.9255, respectively. Lower correlation (r2 = 0.8593) was noted for contrast-enhanced MR angiography and DSA. Respective sensitivity and specificity for detection of hemodynamically relevant stenosis relative to rotational angiography were 100% and 90% for contrast-enhanced MR angiography, 95.5% and 87.2% for 3D TOF MR angiography, and 88.6% and 100% for DSA. Four of 31 severe stenoses were underestimated at DSA, and three were underestimated at contrast-enhanced MR angiography. Three severe stenoses were underestimated at 3D TOF MR angiography, and one was misclassified as occluded. Of 13 moderate (50%-69%) stenoses, one was overestimated at contrast-enhanced MR angiography, two were underestimated and three overestimated at 3D TOF MR angiography, and two were underestimated at DSA. CONCLUSION: DSA results in an underestimation of ICA stenosis compared with rotational angiography. Contrast-enhanced MR angiography correlates best with rotational angiography.     

Contrast-enhanced 3D MR angiography of the carotid artery: comparison with conventional digital subtraction angiography

BACKGROUND AND PURPOSE: Since 1996, several preliminary studies have shown the usefulness of contrast material-enhanced MR angiography for imaging supraaortic vessels. The aim of this study was to compare the accuracy of contrast-enhanced 3D MR angiography with that of digital subtraction angiography (DSA) in the evaluation of carotid artery stenosis. METHODS: A blinded comparison of first-pass contrast-enhanced MR angiography with conventional DSA was performed in 120 patients (240 arteries). MR angiography was performed with a 1.5-T magnet with gradient overdrive equipment, by using a coronal radiofrequency-spoiled 3D fast low-angle-shot sequence after the intravenous injection of gadodiamide. The guidelines of the North American Symptomatic Carotid Endarterectomy Trial for measuring stenosis of the internal carotid artery were applied on maximum intensity projection (MIP) images and conventional catheter angiograms. RESULTS: Grading of stenoses on MR angiograms agreed with grading of stenoses on DSA images in 89% of arteries. In the severe stenosis group (70-99%), agreement was 93%. All internal carotid occlusions (n = 28) and seven of nine pseudo-occlusions were accurately detected with contrast-enhanced MR angiography. The correlation between MR angiography and DSA for determination of minimal, moderate, and severe stenoses and occlusion was statistically significant (r = 0.91, P<.001). CONCLUSIONS: This investigation with a large number of patients confirms that contrast-enhanced MR angiography could become a diagnostic alternative to DSA in the treatment of patients with carotid artery disease.     

Preoperative evaluation of carotid artery stenosis: comparison of contrast-enhanced MR angiography and duplex sonography with digital subtraction angiography

BACKGROUND AND PURPOSE: Contrast-enhanced MR angiography and extracranial color-coded duplex sonography are noninvasive, preoperative imaging modalities for evaluation of carotid artery stenosis. Innovative techniques and improvements in image quality require frequent reassessment of accuracy, reliability, and diagnostic value compared with those of digital subtraction angiography (DSA). We evaluated contrast-enhanced MR angiography and duplex sonography compared with DSA for detection of high-grade carotid artery stenoses. METHODS: Four readers, blinded to clinical symptoms and the outcome of other studies, independently evaluated stenoses on contrast-enhanced MR angiograms in 71 vessels of 39 symptomatic patients. Duplex sonography was also performed in all vessels. The severity of stenosis was defined according to North American Symptomatic Carotid Endarterectomy Trial criteria (0-29%, 30-69%, 70-99%, 100%). Results of both modalities were compared with the corresponding DSA findings. RESULTS: Contrast-enhanced MR angiography had a sensitivity and specificity of 94.9% and 79.1%, respectively, for the identification of carotid artery stenoses of 70% or greater. Sensitivity and specificity of duplex sonography were 92.9% and 81.9%, respectively. Combining data from both tests revealed a sensitivity and specificity of 100% and 81.4%, respectively, for concordant results (80% of vessels). CONCLUSION: Concordant results of contrast-enhanced MR angiography and duplex sonography increase the diagnostic sensitivity to 100%. The reliability of MR angiography is comparable to that of DSA. The combination of contrast-enhanced MR angiography and duplex sonography might be preferable over DSA for preoperative evaluation in most patients, thus reducing the risk of perioperative morbidity and improving the overall outcome.     

Spiral CT angiography and selective digital subtraction angiography of internal carotid artery stenosis.

PURPOSETo determine whether spiral CT angiography allows accurate, quantitative evaluation of anatomic abnormalities, including detection of additional lesions, delineation of plaque morphology, and estimation of degree of internal carotid artery stenosis.METHODSSpiral CT angiography with a maximum intensity projection technique was compared with selective digital subtraction angiography (DSA) in 92 carotid arteries. The category of stenosis was determined according to the North American Symptomatic Carotid Endarterectomy Trial: mild (0% to 29%), moderate (30% to 69%), severe (70% to 99%), and occlusion (100%).RESULTSIn 78 (85%) of the 92 cases, spiral CT angiography and selective DSA demonstrated the same degree of stenosis. All occlusions (n = 19) were diagnosed correctly with spiral CT angiography. Spiral CT angiography agreed with selective DSA in the classification of stenosis in 59% of the group with mild stenosis, in 82% of the group with moderate stenosis, and in 90% of the group with severe stenosis. In the groups with mild (n = 13), moderate (n = 9), and severe (n = 27) stenosis, correlation of spiral CT angiography with selective DSA was significant. Calcified plaques were readily diagnosed with the use of spiral CT angiography but delineation of ulcers was poor. Tandem lesions were not visible owing to the limited coverage.CONCLUSIONSpiral CT angiography is useful for the detection of proximal internal carotid stenoses that are greater than 30%. Depiction of mild stenoses appears to be limited. CT is superior for the detection of calcified plaques but it is not useful for the detection of ulcers.     

Internal carotid artery stenosis: accuracy of subjective visual impression for evaluation with digital subtraction angiography and contrast-enhanced MR angiography

PURPOSE: To prospectively determine, for both digital subtraction angiography (DSA) and contrast material-enhanced magnetic resonance (MR) angiography, the accuracy of subjective visual impression (SVI) in the evaluation of internal carotid artery (ICA) stenosis, with objective caliper measurements serving as the reference standard. MATERIALS AND METHODS: Local ethics committee approval and written informed patient consent were obtained. A total of 142 symptomatic patients (41 women, 101 men; mean age, 70 years; age range, 44-89 years) suspected of having ICA stenosis on the basis of Doppler ultrasonographic findings underwent both DSA and contrast-enhanced MR angiography. With each modality, three independent neuroradiologists who were blinded to other test results first visually estimated and subsequently objectively measured stenoses. Diagnostic accuracy and percentage misclassification for correct categorization of 70%-99% stenosis were calculated for SVI, with objective measurements serving as the reference standard. Interobserver variability was determined with kappa statistics. RESULTS: After exclusion of arteries that were unsuitable for measurement, 180 vessels remained for analysis with DSA and 159 vessels remained for analysis with contrast-enhanced MR angiography. With respect to 70%-99% stenosis, SVI was associated with average misclassification of 8.9% for DSA (8.9%, 7.8%, and 10.0% for readers A, B, and C, respectively) and of 11.7% for contrast-enhanced MR angiography (11.3%, 8.8%, and 15.1% for readers A, B, and C, respectively). Negative predictive values were excellent (92.3%-100%). Interobserver variability was higher for SVI (DSA, kappa = 0.62-0.71; contrast-enhanced MR angiography, kappa = 0.57-0.69) than for objective measurements (DSA, kappa = 0.75-0.80; contrast-enhanced MR angiography, kappa = 0.66-0.72). CONCLUSION: SVI alone is not recommended for evaluation of ICA stenosis with both DSA and contrast-enhanced MR angiography. SVI may be acceptable as an initial screening tool to exclude the presence of 70%-99% stenosis, but caliper measurements are warranted to confirm the presence of such stenosis.     

Evaluation of classic 2D time-of-flight MR angiography in the depiction of severe carotid stenosis

OBJECTIVE: The purpose of this study is to determine the sensitivity, specificity, and clinical utility of classic 2D time-of-flight MR angiography (acquired with derated gradients) as an aid to predicting severe carotid stenosis. SUBJECTS AND METHODS: Our study population was composed of 68 patients, yielding 133 carotid bifurcations for analysis. A 2D time-of-flight MR angiography pulse sequence was modified to provide greater sensitivity for carotid stenosis, which resulted in visualization of a carotid stenosis with a 70% or greater diameter as a signal void. Contrast-enhanced MR angiography was performed with the elliptical centric view order. Multiple overlapping thin-slab acquisition (MOTSA) MR angiography was performed in select patients. Digital subtraction angiography was performed in 51 patients, and the findings were used as the gold standard. In the remaining patients, findings on carotid duplex Doppler sonography and at surgery and clinical follow-up were used as the gold standard. RESULTS: In 51 patients for whom a digital subtraction angiogram was available, we found that the sensitivity of classic 2D time-of-flight MR angiography for prediction of carotid stenosis with a 70% or greater diameter was 94%, and the specificity of the technique was 97%. In three patients with severe carotid stenosis, the stenoses that appeared as signal voids on the classic 2D time-of-flight MR angiography were underestimated on contrast-enhanced MR angiography. Severe stenosis was confirmed by subsequent digital subtraction angiography, surgical results, or both. Discrepancies between findings on MOTSA MR angiography and contrast-enhanced MR angiography were resolved with classic 2D time-of-flight MR angiography. Classic 2D time-of-flight MR angiography increased diagnostic confidence of a severe stenosis in three patients with focal internal carotid artery stenosis. CONCLUSION: Classic 2D time-of-flight MR angiography has a high sensitivity and specificity for predicting carotid bifurcation stenosis of 70% or greater diameter. These probability measures allowed the detection of three significant stenoses that would have been missed on contrast-enhanced MR angiography and provided greater diagnostic confidence than contrast-enhanced or MOTSA MR angiography alone.     

Carotid arterial stenosis: evaluation at CT angiography with the volume-rendering technique.

PURPOSE: To determine whether computed tomographic (CT) angiography with the volume-rendering technique (VRT) can be used to accurately quantify carotid arterial stenosis and to identify occlusions. MATERIALS AND METHODS: Spiral CT was performed in 23 patients who were referred for carotid stenosis evaluation. VRT images and shaded-surface display (SSD) images of 46 carotid arterial bifurcations were compared with findings from digital subtraction angiography (DSA). RESULTS: Agreement on stenosis category between VRT CT angiography and DSA was found in 39 (85%) of the 46 carotid arteries studied. VRT CT angiography was 92% (49 of 53) sensitive and 96% (82 of 85) specific for the detection of grade 2-3 stenoses (> or = 70% stenosis). Agreement on stenosis category between SSD CT angiography and DSA was found in 38 (83%) of the 46 carotid arteries studied. SSD CT angiography was 91% (48 of 53) sensitive and 93% (79 of 85) specific for the detection of grade 2-3 stenoses. Calcified stenoses were correctly graded at VRT CT angiography in 10 of the 10 cases with heavy mural calcified plaques, while eight of the 10 stenoses were accurately quantified at SSD CT angiography. CONCLUSION: These results indicate that VRT CT angiography is as accurate as SSD CT angiography in the evaluation of carotid arterial bifurcations.     

Carotid artery: elliptic centric contrast-enhanced MR angiography compared with conventional angiography

PURPOSE: To determine the accuracy of elliptic centric contrast material-enhanced magnetic resonance (MR) angiography by using conventional angiography as the reference standard. MATERIALS AND METHODS: Fifty patients were examined prospectively with contrast-enhanced MR angiography and conventional angiography. The two examinations were performed within 1 week of each other. Two patients underwent conventional angiography of only one carotid artery, which yielded 98 arteries for comparison. RESULTS: With conventional angiography as the reference standard and by using a 70% threshold for internal carotid arterial diameter stenosis, maximum intensity projection (MIP) images had a sensitivity of 93.3%, specificity of 85.1%, and accuracy of 87.6%, whereas reformatted transverse source images had a sensitivity of 83.3%, specificity of 97.0%, and accuracy of 92.8%. Interobserver variability for conventional angiograms was 0.97, for MIP images was 0.91, and for source images was 0.90. The contrast-enhanced MR angiographic technique had a sensitivity of 88.9% and specificity of 58.1% for the presence of irregularity and/or ulceration. All 50 examinations were triggered appropriately so that minimal or no venous signal intensity was depicted. CONCLUSION: Contrast-enhanced elliptic centric three-dimensional MR angiography offers high-spatial-resolution, venous-suppressed images of the carotid arteries that appear to be adequate to replace conventional angiography in most patients examined prior to carotid endarterectomy.     

Contrast-enhanced carotid MR angiography with commercially available triggering mechanisms and elliptic centric phase encoding

OBJECTIVE. The technical feasibility of contrast-enhanced MR angiography of the carotid arteries was evaluated with routinely available timing sequences and elliptic centric acquisition. The image quality of the contrast-enhanced MR angiography was compared with that of multiple overlapping thin-section acquisition MR angiography (MOTSA MR angiography). SUBJECTS AND METHODS. Sixty-three patients were enrolled. A 2-mL test bolus and commercially available software were used to time the gadolinium bolus. High-resolution contrast-enhanced MR angiography was performed with elliptic centric acquisition. RESULTS. The average time of bolus arrival was 17.3 sec (range, 12-25 sec). In 60 of the 63 patients, we had excellent or good visualization of the carotid bifurcation using contrast-enhanced MR angiography with little or no venous contamination. Two observers ranked delineation of stenosis and morphology of proximal internal carotid artery and overall diagnostic confidence statistically significantly higher for contrast-enhanced MR angiography compared with MOTSA. Ulceration, length of stenosis, and slow flow distal to a critical stenosis were better depicted with contrast-enhanced MR angiography than with MOTSA. Venetian blind artifact, saturation of slow or in-plane flow, and artifactual narrowing in carotid artery kinks plagued MOTSA but were not seen on contrast-enhanced MR angiography. MOTSA was graded superior to contrast-enhanced MR angiography in nine of 120 carotid bifurcations analyzed. CONCLUSION. High-resolution carotid contrast-enhanced MR angiography is technically feasible. We found a 95% success rate using commercially available hardware and software. The image quality with carotid contrast-enhanced MR angiography has improved so that it is equal or superior to the longer MOTSA in most patients.     

Contrast-enhanced MR angiography of the supra-aortic vessels in 24 seconds: a feasibility study

A contrast-enhanced, gradient-echo 3D pulse sequence providing angiographic information in 24 s was tested in five healthy subjects and used prospectively in 21 patients for the investigation of the cervical arteries. Indications included suspected stenosis of the carotid (in 13), or vertebral arteries (in 1), carotid dissection (3), variants of the branches of the aortic arch (2) and extracranial carotid aneurysms (2). The results in all patients were compared with those of intra-arterial digital subtraction angiography (DSA). In patients with carotid stenosis, they were also compared with high-resolution 3D time-of-flight (TOF) MR angiography (MRA). Good quality MR angiograms of the neck vessels were obtained with the fast 3D sequence in 20 of the 21 patients. One claustrophobic patient was unable to co-operate. The degree of internal carotid artery (ICA) stenosis was graded correctly (compared to DSA) in 21 of 24 cases (87.5 %). Two mild stenoses were overestimated as moderate using the fast MR sequence and one high-grade stenosis was misdiagnosed as a complete occlusion. Carotid dissection was confirmed in one case and correctly excluded in two. Four extracranial ICA aneurysms in two patients, arterial variants and stenosis of the origin of the vertebral artery were correctly diagnosed using the contrast-enhanced MR angiogram. Three-dimensional TOF MRA was unsuccessful due to motion artefacts in half of the cases of ICA stenosis. Received: 6 August 1998 Accepted: 21 December 1998     

Multi-detector row CT angiography in the assessment of carotid artery disease in symptomatic patients: comparison with rotational angiography and digital subtraction angiography

BACKGROUND AND PURPOSE: Compared with the single-detector technique, multi-detector row CT angiography permits larger anatomic coverage that includes both the epiaortic and entire carotid circulations. We evaluated the accuracy of multi-detector row CT angiography by using multiplanar reformation (MPR) for measuring carotid artery diameters compared with that of rotational angiography. We also evaluated the diagnostic performance of CT angiography compared with digital subtraction angiography (DSA). METHODS: In 35 patients, CT angiograms of 70 carotid arteries were compared with DSA images, and CT angiograms of 33 carotid arteries were compared with rotational angiograms. CT angiographic interpretation was performed first interactively at a workstation. Diameter measurements of normal and stenosed carotid arteries were performed on cross-sectional and oblique sagittal MPRs. Degree of stenosis was calculated per North American Symptomatic Carotid Endarterectomy Trial criteria independently by two observers for each technique. RESULTS: Degree of stenosis was slightly underestimated with CT angiography, with mean differences (+/- SD) per observer of 6.9 +/- 17.6% and 10.7 +/- 16.1% for cross-sectional and 2.8 +/- 19.2% and 9.1 +/- 16.8% for oblique sagittal MPRs compared with rotational angiography. CT angiography was somewhat inaccurate for measuring the absolute minimal diameter of high-grade stenoses. On symptomatic sides (n = 35), interactive CT angiographic interpretation combined with MPR measurements for lesions with a visual estimate of 50% or greater stenosis achieved a sensitivity of 95% (20/21) and specificity of 93% (13/14) in the detection of carotid stenosis (>/= 50%) verified with DSA. CONCLUSION: Regardless of slight underestimation of carotid stenosis with CT angiography compared with rotational angiography, diagnostic performance of CT angiography with interactive interpretation proved to be good. Also, the method is highly sensitive for detection of carotid artery stenosis, indicating the suitability of CT angiography as a screening method for symptomatic patients. For hemodynamically significant stenoses revealed by CT angiographic screening, conventional angiography still seems to be necessary.     

Multidirectional depiction of internal carotid arterial stenosis: three-dimensional time-of-flight MR angiography versus rotational and conventional digital subtraction angiography

PURPOSE: To evaluate whether and to what extent greater number of projection images obtained at three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiography versus conventional digital subtraction angiography (DSA) causes overestimation of internal carotid arterial (ICA) stenosis. MATERIALS AND METHODS: DSA (two or three projections), rotational angiography (16 or 32 projections), and 3D TOF MR angiography (12 projections) were performed in 47 stenotic ICAs of 38 symptomatic patients. Two observers independently measured maximum stenosis, and the mean differences among MR angiography, DSA, and rotational angiography were compared. RESULTS: Three rotational and five MR angiograms were nondiagnostic. Seven MR angiograms of ICA stenoses showed a signal void and were excluded from analysis. On the remaining 32 angiograms, mean differences in maximum stenosis for observers 1 and 2, respectively, were 7% (95% CI: 3%, 12%) and 8% (95% CI: 3%, 13%) at MR angiography versus DSA and 2% (95% CI: -2%, 7%) and -1% (95% CI: -5%, 3%) at MR angiography versus rotational angiography. ICA stenosis was graded significantly higher at MR angiography versus DSA, whereas, it was not overestimated at MR angiography versus rotational angiography. The difference in maximum stenosis at MR angiography versus DSA was significantly different from that of MR angiography versus rotational angiography. CONCLUSION: Apparent overestimation of ICA stenosis at 3D TOF MR angiography versus conventional DSA may be partly explained by the greater number of projection images available at 3D TOF MR angiography.     

Stenosis detection with MR angiography and digital subtraction angiography in dysfunctional hemodialysis access fistulas and grafts

PURPOSE: To prospectively assess three-dimensional contrast material-enhanced magnetic resonance (MR) angiography for stenosis depiction in malfunctioning hemodialysis arteriovenous fistulas (AVFs) and grafts (AVGs), as compared with digital subtraction angiography (DSA). MATERIALS AND METHODS: Ethical review board approval and written informed consent were obtained. MR angiography and DSA were performed in 51 dysfunctional hemodialysis fistulas and grafts in 48 consecutive patients. Vascular tree of accesses was divided into between three and eight segments depending on access type (AVF or AVG) and length of venous outflow. Images obtained with MR and DSA were interpreted by two MR radiologists and two interventional radiologists, respectively, who were blinded to information from each other and other studies. DSA was reference standard for stenosis detection. Sensitivity, specificity, and predictive values with 95% confidence intervals (CIs) of contrast-enhanced MR in detection of vascular segments containing hemodynamically significant (> or =50%) stenosis were calculated. Linear-weighted kappa statistic was calculated for contrast-enhanced MR and DSA to determine interobserver agreement regarding stenosis detection. RESULTS: A total of 282 vascular segments were evaluated. Contrast-enhanced MR depicted three false-positive stenoses and all but two of 70 significant stenoses depicted with DSA. Sensitivity, specificity, and positive and negative predictive values of MR in detection of vessel segments with significant stenoses were 97% (95% CI: 90%, 99%), 99% (95% CI: 96%, 100%), 96% (95% CI: 88%, 99%), and 99% (95% CI: 97%, 100%), respectively. MR demonstrated significant stenosis in four of five nondiagnostic DSA segments, whereas DSA showed no significant stenosis in four nondiagnostic MR segments. Linear-weighted kappa statistic for interobserver agreement regarding stenosis detection was 0.92 (95% CI: 0.89, 0.95) for MR and 0.95 (95% CI: 0.92, 0.97) for DSA. CONCLUSION: MR angiography depicts stenoses in dysfunctional hemodialysis accesses but has limited clinical value as result of current inability to perform MR-guided access interventions after stenosis detection. MR of dysfunctional access should be considered only if nondiagnostic vascular segment is present at DSA.     

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.     

Prospective evaluation of suspected stenoocclusive disease of the intracranial artery: combined MR angiography and CT angiography compared with digital subtraction angiography

BACKGROUND AND PURPOSE: MR angiography is primarily and increasingly used to assess intracranial arterial stenoocclusion. However, MR angiography can cause overestimation of stenosis. Although CT angiography is accurate, it has limitations. Our purpose was to determine whether the accuracy of combined MR angiography and CT angiography is equal to that of digital subtraction angiography (DSA) in measuring stenosis and detecting major intracranial arterial occlusion. METHODS: CT angiography and intraarterial DSA were prospectively performed in 18 patients with suspected intracranial stenoocclusive disease, as revealed with MR angiography. Before DSA, two reviewers independently assessed MR intracranial angiograms. Subsequently, they assessed CT angiograms with MR angiograms. Results were compared with DSA results. The degree of stenoocclusion was categorized; stenosis of 50% or more indicated stenoocclusive disease. After the blinded study, two radiologists retrospectively reviewed the angiographic findings. RESULTS: Stenoocclusive disease was identified in 18 of 198 intracranial arteries at DSA. MR angiography had a sensitivity of 92%, a specificity of 91%, and an accuracy of 91% for the identification of stenosis of 50% or more; the addition of CT angiography yielded values of 100%, 99%, and 99%, respectively. Stenotic grades with combined CT angiography and MR angiography agreed with those of DSA in 98% of cases. In the retrospective study, CT angiography did not always correctly delineate arterial lumina with circumferential calcification and cavernous portions of the internal carotid artery. CONCLUSION: In this investigation, the evaluation of suspected stenoocclusive diseases in major intracranial arteries, the accuracy of combined MR angiography and CT angiography is equal to that of DSA in most cases.     

Time-resolved contrast-enhanced magnetic resonance angiography of the carotid arteries: diagnostic accuracy and inter-observer variability compared with selective catheter angiography

RATIONALE AND OBJECTIVES: To assess the diagnostic accuracy and interobserver variability of contrast-enhanced magnetic resonance angiography (CE-MRA) in a time-resolved technique compared with digital subtraction angiography (x-ray DSA) in patients with suspected stenoses of the internal carotid artery. MATERIALS AND METHODS: A total of 43 patients were enrolled in this prospective study. All patients underwent selective x-ray DSA involving a total of 84 carotid arteries. CE-MRA was performed in a time-resolved technique with a fast gradient-echo sequence on a 1.5 T MR scanner: TR 3.8 milliseconds, TE 1.49 milliseconds. Four consecutive measurements, each a duration of 10 seconds, were performed with omission of measuring bolus transit time. Four independent radiologists scored the degree of stenosis. The interobserver variability was calculated for CE-MRA and x-ray DSA. RESULTS: In the 43 cases, at least one MRA measurement showed arterial contrast without venous degradation. Compared with x-ray DSA the mean sensitivity and specificity for grading stenosis > or = 70% were 98% and 86%, respectively. The interobserver agreement was substantial with no significant difference between CE-MRA (kappa value 0.794) and x-ray DSA (kappa value 0.786). CONCLUSIONS: The short acquisition time of a fast CE-MRA sequence allows a selective visualization of the internal carotid arteries without degradation from venous enhancement. It is a reliable method with a good interobserver agreement.     

脊髓血管畸形的快速增强MRA与DSA诊断的比较研究

目的 评价椭圆形中心顺序(elliptic centric ordered)的快速增强磁共振血管成像(fastcontrast-enhanced MR angiography,CE-MRA)在脊髓血管畸形中的诊断和临床应用价值.方法 25例临床怀疑脊髓血管畸形的患者在1.5T MR机上接受了椭圆形中心顺序的快速CE-MRA检查,所有病例行选择性全脊椎动脉造影,18例施行了外科手术,其中2例术前行血管内栓塞,术后MRA随访了10例;以选择性全脊椎动脉造影为金标准,就病变诊断、供养动脉起源、供养动脉、瘘口或瘤巢、引流静脉和血管的图像质量(包括血管的连续性、强化程度和清晰度)进行MRA和DSA的比较.结果 经外科手术证实18例,包括脊髓动静脉畸形3例、髓周动静脉瘘5例、硬膜动静脉瘘7例、椎旁动静脉瘘1例、自发性椎管内硬膜外血肿2例;MRA显示脊髓血管畸形的诊断、供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉与DSA的符合率分别为93.8%、92%、96.2%、100%和100%,MRA显示血管强化和清晰度类似于DSA(P＞0.05),DSA显示血管的连续性优于MRA(P＜0.05);9例MRA未见椎管内异常血管,与DSA完全符合.术后MRA随访的10例原异常血管未再显示.结论 椭圆形中心顺序的快速CE-MRA能够初步诊断脊髓血管畸形的亚型,能够显示脊髓血管畸形的供养动脉起源、供养动脉、瘤巢或瘘口、引流静脉,能够指导选择性脊椎动脉造影和手术治疗,是脊髓血管畸形术前诊断和术后随访的重要手段.     

MR angiography of internal carotid arteries: breath-hold Gd-enhanced 3D fast imaging with steady-state precession versus unenhanced 2D and 3D time-of-flight techniques

PURPOSE: The purpose of this work was to compare Gd-enhanced breath-hold fast imaging with steady-state precession (Gd-FISP) with unenhanced time-of-flight (TOF) sequences in evaluating internal carotid arteries (ICAs). METHOD: Thirty patients underwent three unenhanced TOF sequences [2D traveling saturation (Travelsat); 3D tilted optimized nonsaturated excitation (TONE); TOF 3D Multislab] and two breath-hold 3D Gd-FISP sequences with automated intravenous contrast agent injection (axial and coronal). ICAs were classified as normal (no stenosis); with mild (<30%), moderate (30-70%), or severe stenosis; or occluded (100%). Digital subtraction angiography (DSA) with aortic arch injection was used as a reference technique. RESULTS: DSA revealed 20 normal ICAs; 11 mild, 9 moderate, and 14 severe stenoses; and 2 occlusions. DSA and all MR angiography (MRA) sequences diagnosed the occlusion of four common carotid arteries. The TOF 2D overestimated 10 stenoses, TOF 3D TONE 9, and TOF 3D Multislab 5; Gd-FISP 3D overestimated only 2 of them, reaching the highest sensitivity and specificity for severe stenoses. Significant differences were found between the overestimation of Gd-FISP and each of the three unenhanced sequences (0.0020 < p < 0.0313, Wilcoxon and McNemar tests). Severe artifacts were observed with TOF techniques only. CONCLUSION: Gd-FISP is an interesting, largely artifact-free improvement for MRA of ICAs.     

Contrast-enhanced magnetic resonance angiography in the evaluation of peripheral bypass grafts

The aim of this study was to determine the potential of contrast-enhanced magnetic resonance (MR) angiography in the evaluation of peripheral bypass grafts. Digital subtraction angiography (DSA) served as a standard of reference. Thirty-five patients with previous bypass graft surgery underwent DSA and contrast-enhanced MR angiography within 2 weeks. MR angiography was performed using a three-dimensional fast gradient-echo sequence after administration of gadopentetate dimeglumine. Every leg was divided into 11 segments and scored in five categories of stenosis. MR angiography findings were compared with those of DSA. A total of 38 bypass grafts and 454 segments in 27 patients were included in the evaluation. In 33 (87 %) bypass grafts stenosis grading with both methods corresponded, and in 5 (13 %) cases stenosis was overestimated on MR angiography. Agreement in detection of hemodynamically significant stenosis (stenosis = 50 %) was 94.7 % with a sensitivity of 100 % and a specificity of 91.3 %. In 340 (83.0 %) vascular segments there was conformity in graduation, in 69 (16.88 %), there was a difference of one or more grades on MR angiograms. Forty-four segments (9.6 %) were not assessable due to technical limitations. Contrast-enhanced MR angiography is an useful noninvasive tool in the detection of failing peripheral vascular bypass grafts. Received: 6 July 1999; Revised: 12 November 1999; Accepted: 4 January 2000     

High-spatial-resolution contrast-enhanced MR angiography of the renal arteries: a prospective comparison with digital subtraction angiography

PURPOSE: To evaluate a high-spatial-resolution three-dimensional (3D) contrast material-enhanced magnetic resonance (MR) angiographic technique for detecting proximal and distal renal arterial stenosis. MATERIALS AND METHODS: Twenty-five patients underwent high-spatial-resolution small-field-of-view (FOV) 3D contrast-enhanced MR angiography of the renal arteries, which was followed several minutes later by more standard, large-FOV 3D contrast-enhanced MR angiography that included the distal aorta and iliac arteries. For both acquisitions, MR fluoroscopic triggering and an elliptic centric view order were used. Two readers evaluated the MR angiograms for grade and hemodynamic significance of renal arterial stenosis, diagnostic quality, and presence of artifacts. MR imaging results for each patient were compared with those of digital subtraction angiograms. RESULTS: The high-spatial-resolution small-FOV technique provided high sensitivity (97%) and specificity (92%) for the detection of renal arterial stenosis, including all four distal stenoses encountered. The portrayal of the segmental renal arteries was adequate for diagnosis in 19 (76%) of 25 patients. In 12% of the patients, impaired depiction of the segmental arteries was linked to motion. CONCLUSION: The combined high-spatial-resolution small-FOV and large-FOV MR angiographic examination provides improved spatial resolution in the region of the renal arteries while maintaining coverage of the abdominal aorta and iliac arteries.