Contrast Material-enhanced Magnetic Resonance Angiography Research Articles

Collateral and permeability imaging derived from dynamic contrast material-enhanced MR angiography in prediction of PH 2 hemorrhagic transformation after acute ischemic stroke: a pilot study.

To evaluate the role of collateral and permeability imaging derived from dynamic contrast material-enhanced magnetic resonance angiography to predict PH 2 hemorrhagic transformation in acute ischemic stroke. The secondary analysis of a published data from participants with acute ischemic stroke. The multiphase collateral map and permeability imaging were generated by using dynamic signals from dynamic contrast material-enhanced magnetic resonance angiography obtained at admission. To identify independent predictors of PH 2 hemorrhagic transformation, age, sex, risk factors, baseline National Institutes of Health Stoke Scale (NIHSS) score, baseline DWI lesion volume, collateral-perfusion status, mode of treatment, and successful early reperfusion were evaluated with multiple logistic regression analyses and the significance of permeability imaging in prediction of PH 2 hemorrhagic transformation was evaluated by subgroup analysis. In 115 participants, including 70 males (mean (SD) age, 69 (12) years), PH 2 hemorrhagic transformation occurred in 6 participants with very poor collateral-perfusion status (MAC 0). MAC 0 (OR, 0.06; 95% CI, 0.01, 0.74; P = .03) was independently associated with PH 2 hemorrhagic transformation. In 22 participants with MAC 0, the permeable signal on Kep permeability imaging was the only significant characteristic associated with PH 2 hemorrhagic transformation (P = .009). The specificity of Kep permeability imaging was 93.8% (95% confidence interval: 69.8, 99.8) in predicting PH 2 hemorrhagic transformation. Individual-based prediction of PH 2 hemorrhagic transformation in patients with acute ischemic stroke may be possible with multiphase collateral map and permeability imaging derived from dynamic contrast material-enhanced magnetic resonance angiography.

Unenhanced MR Angiography of the Foot: Initial Experience of Using Flow-Sensitive Dephasing–prepared Steady-State Free Precession in Patients with Diabetes

To assess image quality and diagnostic performance of unenhanced magnetic resonance (MR) angiography with use of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) of the foot arteries in patients with diabetes. This prospective study was approved by institutional review board. Informed consent was obtained from all subjects. Thirty-two healthy volunteers and 38 diabetic patients who had been scheduled for lower-extremity contrast material-enhanced MR angiography were recruited to undergo unenhanced MR angiography with a 1.5-T MR unit. Image quality and diagnostic accuracy of unenhanced MR angiography in the detection of significant arterial stenosis (≥50%) were assessed by two independent reviewers. Contrast-enhanced MR angiography was used as the reference standard. The difference in the percentage of diagnostic arterial segments at unenhanced MR angiography between healthy volunteers and diabetic patients was evaluated with the McNemar test and generalized estimating equation for correlated data. Signal-to-noise ratio (SNR) and artery-to-muscle contrast-to-noise ratio (CNR) of pedal arteries were measured and compared between the two MR angiography techniques by using the paired t test. All subjects successfully underwent unenhanced MR angiography of the foot. Unenhanced MR angiography yielded a high percentage of diagnostic arterial segments in both healthy volunteers (303 of 320 segments, 95%) and patients (341 of 370 segments, 92%), and there was no difference in the percentage between the two populations (P = .195). In patients, the average SNR and CNR at unenhanced MR angiography were higher than those at contrast-enhanced MR angiography (SNR: 90.7 ± 38.1 vs 81.7 ± 34.7, respectively, P = .023; CNR: 85.2 ± 33.2 vs 76.6 ± 33.5, respectively, P = .013). The average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of unenhanced MR angiography were 88% (35 of 40 segments), 93% (107 of 115 segments), 81% (35 of 43 segments), 96% (107 of 112 segments), and 92% (142 of 155 segments), respectively. Interobserver agreement between the two readers for diagnostic accuracy was good (κ = 0.83). Unenhanced MR angiography with use of FSD-prepared SSFP allows clear depiction of the foot arterial tree and accurate detection of significant arterial stenosis. The technique has the potential to be a safe and reliable screening tool for the assessment of foot arteries in diabetic patients without the use of gadolinium-based contrast material.

Comparison of Nonenhanced MR Angiographic Subtraction Techniques for Infragenual Arteries at 1.5 T: A Preliminary Study

To evaluate diagnostic performance of three nonenhanced methods: variable-refocusing-flip angle (FA) fast spin-echo (SE)-based magnetic resonance (MR) angiography (variable FA MR) and constant-refocusing-FA fast SE-based MR angiography (constant-FA MR) and flow-sensitive dephasing (FSD)-prepared steady-state free precession MR angiography (FSD MR) for calf arteries, with dual-injection three-station contrast material-enhanced MR angiography (gadolinium-enhanced MR) as reference. This prospective study was institutional review board approved and HIPAA compliant, with informed consent. Twenty-one patients (13 men, eight women; mean age, 62.6 years) underwent calf-station variable-FA MR, constant-FA MR, and FSD MR at 1.5 T, with gadolinium-enhanced MR as reference. Image quality and stenosis severity were assessed in 13 segments per leg by two radiologists blinded to clinical data. Combined constant-FA MR and FSD MR reading was also performed. Methods were compared (logistic regression for correlated data) for diagnostic accuracy. Of 546 arterial segments, 148 (27.1%) had a hemodynamically significant (≥ 50%) stenosis. Image quality was satisfactory for all nonenhanced MR sequences. FSD MR was significantly superior to both other sequences (P < .0001), with 5-cm smaller field of view; 9.6% variable-FA MR, 9.6% constant-FA MR, and 0% FSD MR segmental evaluations had nondiagnostic image quality scores, mainly from high diastolic flow (variable-FA MR) and motion artifact (constant-FA MR). Stenosis sensitivity and specificity were highest for FSD MR (80.3% and 81.7%, respectively), compared with those for constant-FA MR (72.3%, P = .086; and 81.8%, P = .96) and variable-FA MR (75.9%, P = .54; and 75.6%, P = .22). Combined constant-FA MR and FSD MR had superior sensitivity (81.8%) and specificity (88.3%) compared with constant-FA MR (P = .0076), variable-FA MR (P = .0044), and FSD MR (P = .0013). All sequences had an excellent negative predictive value (NPV): 93.2%, constant-FA MR; 94.7%, variable-FA MR; 91.7%, FSD MR; and 92.9%, combined constant-FA MR and FSD MR. At 1.5 T, all evaluated nonenhanced MR angiographic methods demonstrated satisfactory image quality and excellent NPV for hemodynamically significant stenosis. http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120859/-/DC1.

Peripheral Arterial Occlusive Disease: 3.0-T versus 1.5-T MR Angiography Compared with Digital Subtraction Angiography

To prospectively evaluate the diagnostic accuracy of 3-T versus 1.5-T contrast material-enhanced (CE) magnetic resonance (MR) angiography with high spatial resolution in patients who have peripheral arterial occlusive disease, with conventional digital subtraction angiography (DSA) serving as the reference standard. Institutional review board approval and written informed consent were obtained. DSA and standardized single-injection, three-station, moving-table CE MR angiography, with similar acquisition protocols and contrast agent doses at 3 T and 1.5 T, were consecutively performed in 19 patients (13 men and six women; mean age ± standard deviation, 67 years ± 9). Stenosis was scored visually in 500 arterial segments (97.5% of all available) in consensus by two radiologists in a blinded manner (the radiologists were unaware of the field strength and prior DSA and MR angiographic results and used randomized analysis order). Contrast-to-noise ratio was determined in the vascular tree of both legs. Statistical significance in stenosis scoring was evaluated by using generalized estimating equations. Contrast-to-noise differences were evaluated with paired t tests. Agreement between MR angiography and DSA was evaluated by using Fleiss-Cohen κ statistics. Both 3-T and 1.5-T CE MR angiography showed similar excellent agreement with DSA regarding stenosis classification (κ = 0.96 and 0.93, respectively). All sensitivity and specificity values exceeded 90%. Mean contrast-to-noise ratio was 3.0-4.2 times higher at 3 T than at 1.5 T. Standardized single-injection, three-station, moving-table 3-T CE MR angiography is reliable for classification of stenosis in patients suspected of having peripheral arterial occlusive disease, and diagnostic performance was similar to that seen with 1.5-T MR angiography. There was a significantly increased contrast-to-noise ratio for identical contrast agent dose at 3-T MR angiography.

Evaluation of Peripheral Arterial Disease with Nonenhanced Quiescent-Interval Single-Shot MR Angiography

To assess the diagnostic performance of quiescent-interval single-shot (QISS) magnetic resonance (MR) angiography, a nonenhanced two-dimensional electrocardiographically gated single-shot balanced steady-state free precession examination for the evaluation of symptomatic chronic lower limb ischemia. For this prospective institutional review board-approved, HIPAA-compliant study, the institutional review board waived the requirement for informed patient consent. The QISS nonenhanced MR angiography technique was evaluated in a two-center trial involving 53 patients referred for lower extremity MR angiography for suspected or known chronic peripheral arterial disease (PAD), with contrast material-enhanced MR angiography serving as the noninvasive reference standard. The accuracy of stenosis assessments performed with the nonenhanced MR angiography sequence was evaluated relative to the reference standard. Per-segment, per-region, and per-limb sensitivities and specificities were calculated, and assessments were considered correct only if they were in exact agreement with the reference standard-derived assessments. Generalized estimating equation (GEE) modeling with use of an unstructured binomial logit analysis was used to account for clustering of multiple measurements per case. The sensitivity and specificity of QISS MR angiography for the determination of nonsignificant (<50%) versus significant (50%-100%) stenosis were compared with the sensitivity and specificity of the reference standard. The diagnostic performance of nonenhanced MR angiography was found to be nearly equivalent to the diagnostic performances of contrast-enhanced MR angiography and digital subtraction angiography. Non-GEE segment-based analysis revealed that for the two reviewers, nonenhanced MR angiography had sensitivities of 89.7% (436 of 486 segments) and 87.0% (423 of 486 segments) and specificities of 96.5% (994 of 1030 segments) and 94.6% (973 of 1028 segments). QISS nonenhanced MR angiography offers an alternative to currently used imaging tests for symptomatic chronic lower limb ischemia, for which the administration of iodinated or gadolinium-based contrast agents is contraindicated.

Nonenhanced MR Angiography of the Hand with Flow-Sensitive Dephasing–prepared Balanced SSFP Sequence: Initial Experience with Systemic Sclerosis

To compare the image quality and degree of vessel narrowing at flow-sensitive dephasing (FSD) magnetic resonance (MR) angiography of the hands with those at contrast material-enhanced MR angiography of the hands in patients with systemic sclerosis. In a single-center study with institutional review board approval and HIPAA compliance, six healthy volunteers and six patients with systemic sclerosis were imaged at 1.5-T nonenhanced FSD MR angiography followed by contrast-enhanced MR angiography. Sixteen vascular segments in four vessel groups were evaluated for image quality and assessed semiquantitatively for stenosis degree by using Likert scales. The nonparametric Wilcoxon signed rank test was used to perform pairwise comparisons of the MR angiographic techniques. P < .05 indicated statistical significance. Performing FSD MR angiography, as compared with time-resolved MR angiography and high-spatial-resolution MR angiography, improved the image quality for all arterial segments combined in the control (mean score, 2.9 [FSD] vs 3.7 [time-resolved technique] and 3.1 [high-spatial-resolution technique]) and patient (mean score, 4.0 [FSD] vs 4.2 [time-resolved technique] and 4.3 [high-spatial-resolution technique]) groups. In the control subjects, FSD angiography depicted proper digital artery stenosis that was less severe (mean grade, 0.7) than that seen with the time-resolved (mean grade, 1.6) and high-spatial-resolution (mean grade, 1.0) techniques. In the patient group, FSD angiography depicted lower degrees of stenosis, with a lower mean grade for all segments combined (1.3) compared with the corresponding mean grades for time-resolved (1.5) and high-spatial-resolution (1.8) MR angiography. Preliminary data indicate that the proposed nonenhanced FSD MR angiographic technique is an improvement over existing contrast-enhanced techniques for evaluation of the hand vasculature in vasospastic disorders of the hand. Further technical improvements and a systematic clinical study are warranted.

Renal Arteries: Isotropic, High-Spatial-Resolution, Unenhanced MR Angiography with Three-dimensional Radial Phase Contrast

To prospectively compare a new three-dimensional (3D) radial phase-contrast magnetic resonance (MR) angiographic method with contrast material-enhanced MR angiography for anatomic assessment of the renal arteries. An institutional review board approved this prospective HIPAA-compliant study. Informed consent was obtained. Twenty-seven subjects (mean age, 52.6 years ± 20.5 [standard deviation]) were imaged with respiratory-gated phase-contrast vastly undersampled isotropic projection reconstruction (VIPR) prior to contrast-enhanced MR angiographic acquisition with a 3.0-T clinical system. The imaging duration for phase-contrast VIPR was 10 minutes and provided magnitude and complex difference ("angiographic") images with 3D volumetric (320 mm) coverage and isotropic high spatial resolution (1.25 mm(3)). Quantitative analysis consisted of comparing vessel diameters between the two techniques. Qualitative assessment included evaluation of the phase-contrast VIPR and contrast-enhanced MR angiographic techniques for artifacts, noise, and image quality. Bland-Altman analysis was used for comparison of quantitative measurements, and the Wilcoxon signed rank test was used for comparison of qualitative scores. Phase-contrast VIPR images were successfully acquired in all subjects. The vessel diameters measured with phase-contrast VIPR were slightly greater than those measured with contrast-enhanced MR angiography (mean bias = 0.09 mm). Differences in mean artifact, quality scores for the proximal renal arteries, and overall image quality scores between phase-contrast VIPR and contrast-enhanced MR angiographic techniques were not statistically significant (P = .31 and .29, .27 and .39, and .43 and .69 for readers 1 and 2, respectively). The quality scores for the segmental renal arteries were higher for phase-contrast VIPR than for contrast-enhanced MR angiography (P < .05). Although the noise scores were higher with phase-contrast VIPR than with contrast-enhanced MR angiography and were statistically significant (P < .05), the presence of noise did not interfere with the ability to interpret the images. Isotropic, high-spatial-resolution, unenhanced MR angiography of the renal arteries is feasible with 3D radial undersampling.

Intracranial Aneurysms Treated with Coil Placement: Test Characteristics of Follow-up MR Angiography—Multicenter Study

To determine the test characteristics of magnetic resonance (MR) angiography in the assessment of occlusion of aneurysms treated with coil placement. This was an ethics committee-approved multicenter study. written informed consent was obtained in 311 patients with 343 aneurysms, who had been treated with coil placement and were scheduled for routine follow-up with intraarterial digital subtraction angiography (DSA). Thirty-five patients participated two or three times. Either 3.0- or 1.5-T time-of-flight (TOF) and contrast material-enhanced MR angiography were performed in addition to intraarterial DSA. Aneurysm occlusion was evaluated by independent readers at DSA and MR angiography. The test characteristics of MR angiography were assessed by using DSA as the standard. The area under the receiver operating characteristic curve (AUC) was calculated for 3.0- versus 1.5-T MR angiography and for TOF versus contrast-enhanced MR angiography, and factors associated with discrepancies between MR angiography and DSA were assessed with logistic regression. Aneurysm assessments (n = 381) at DSA and MR angiography were compared. Incomplete occlusion was seen at DSA in 88 aneurysms (23%). Negative predictive value of MR angiography was 94% (95% confidence interval [CI]: 91%, 97%), positive predictive value was 69% (95% CI: 60%, 78%), sensitivity was 82% (95% CI: 72%, 89%), and specificity was 89% (95% CI: 85%, 93%). AUCs were similar for 3.0- (0.90 [95% CI: 0.86, 0.94]) and 1.5-T MR (0.87 [95% CI: 0.78, 0.95]) and for TOF MR (0.86 [95% CI: 0.81, 0.91]) versus contrast-enhanced MR (0.85 [95% CI: 0.80, 0.91]). A small residual lumen (odds ratio, 2.1 [95% CI: 1.1, 4.3]) and suboptimal projection at DSA (odds ratio, 5.5 [95% CI: 1.5, 21.0]) were independently associated with discordance between intraarterial DSA and MR angiography. Documentation of good diagnostic performance of TOF MR angiography at both 1.5 and 3.0 T in the current study represents an important step toward replacing intraarterial DSA with MR angiography in the follow-up of patients with aneurysms treated with coils.

Carotid Artery Stenosis: Accuracy of Noninvasive Tests—Individual Patient Data Meta-Analysis

To find clinically relevant estimates of the accuracy of noninvasive imaging-Doppler ultrasonography (US), computed tomographic (CT) angiography, magnetic resonance (MR) angiography, and contrast material-enhanced MR angiography-in diagnosing both severe and moderate symptomatic carotid artery stenosis; to ascertain the effect of prespecified clinical factors and clinical setting on diagnostic accuracy; and to estimate the probability of agreement between two noninvasive tests. Original principal investigators obtained ethics approval for each data set. All data were anonymized. Individual patient data sets (IPDs) for noninvasive imaging tests were used to determine sensitivity, specificity, and agreement between the tests for symptomatic carotid artery stenosis; to compare ipsilateral with contralateral arteries; to compare IPDs with literature estimates; to compare routine audit and research data; and to determine the effect of age and sex on sensitivity and specificity. Contrast-enhanced MR angiography was the most accurate (sensitivity, 0.85 [30 of 35]; 95% confidence interval [CI]: 0.69, 0.93; and specificity, 0.85 [67 of 78]; 95% CI: 0.76, 0.92) for 70%-99% symptomatic stenosis. Sensitivity for a 50%-69% stenosis was poor, although data were limited. Sensitivity and specificity were generally lower in the ipsilateral than in the contralateral artery. IPD estimates were lower than literature values. Results of comparison of research with audit-derived data were inconclusive. Neither age nor sex affected accuracy. Agreement was better between two Doppler US tests and between two contrast-enhanced MR angiographic tests than it was between Doppler US and contrast-enhanced MR angiography, except for a 70%-99% symptomatic stenosis. Primary studies should distinguish ipsilateral from contralateral arteries and carefully describe the patients' characteristics and study environment. The literature overestimates noninvasive imaging accuracy. More data are needed to inform physicians in routine clinical practice.

Renal Transplant: Nonenhanced Renal MR Angiography with Magnetization-prepared Steady-State Free Precession

The institutional review board approved this HIPAA-compliant study and waived informed consent. The purpose was to investigate nonenhanced magnetic resonance (MR) angiography with steady-state free precession (SSFP) with inversion recovery for assessing renal arteries in patients with renal transplants. Thirteen recipients of renal transplants underwent SSFP MR angiography before contrast material-enhanced MR angiography. Three stenoses (two mild, one severe) were identified at SSFP MR angiography in agreement with findings at contrast-enhanced MR angiography. There was no significant difference in image quality between the two methods. Results suggest SSFP MR angiography permits image quality of renal transplant arteries and detection of arterial stenosis comparable with those at contrast-enhanced MR angiography.

Pulmonary Vein Imaging with Unenhanced Three-dimensional Balanced Steady-State Free Precession MR Angiography: Initial Clinical Evaluation

To determine whether unenhanced magnetic resonance (MR) angiography performed with a three-dimensional (3D) segmented steady-state free precession (SSFP) sequence would be an alternative to contrast material-enhanced MR angiography for evaluating pulmonary veins (PVs) prior to and following radiofrequency (RF) ablation for atrial fibrillation. MR angiographic examinations of PVs, performed in 20 patients (nine men, 11 women; mean age, 56.4 years +/- 12.7 [standard deviation]), were retrospectively reviewed according to an institutional review board-approved protocol. The number of PVs and their orthogonal measurements obtained from the 3D SSFP images were compared with those obtained from contrast-enhanced MR angiography. Signal-to-noise and contrast-to-noise ratios were also compared. Qualitative assessment of both techniques was performed by independent reviewers who scored the image quality (on a scale of 1 to 5) on the basis of PV conspicuity. The presence of cardiac and extracardiac pathologic indicators was also determined. Bland-Altman and Wilcoxon signed rank statistical analyses were performed. The mean difference in PV diameter measurements between contrast-enhanced MR angiography and 3D SSFP was -0.02 cm +/- 0.25. Signal-to-noise and contrast-to-noise ratios were higher for 3D SSFP images than for contrast-enhanced MR angiograms. Qualitatively, there was no significant difference in PV conspicuity between the techniques. Noncardiac pathologic indicators were detected in 10 of 20 patients on 3D SSFP images but not on contrast-enhanced MR angiograms. Unenhanced PV MR angiography performed by using a free-breathing 3D SSFP technique is as accurate as contrast-enhanced MR angiography for measuring PV diameter. This technique can be used for patients in whom contrast-enhanced computed tomographic or MR angiography is contraindicated and may be sufficient in all patients.

High-Spatial-Resolution Lower Extremity MR Angiography at 3.0 T: Contrast Agent Dose Comparison Study

To determine whether contrast material dose reduction at 3.0 T allows preserved image quality for high-spatial-resolution magnetic resonance (MR) angiography of the lower extremities. Forty-five consecutive patients (27 men, 18 women; mean age, 64 years) underwent contrast material-enhanced MR angiography of the lower extremities at 3.0 T. A waiver of informed consent was granted by the institutional review board. Sixteen patients received high-dose (approximately 0.3 mmol/kg), 15 received intermediate-dose (approximately 0.2 mmol/kg), and 14 received low-dose (approximately 0.1 mmol/kg) gadopentetate dimeglumine during a three-station, dual-injection examination. For scoring purposes, the arterial system from the celiac trunk to the plantar arteries was divided into 34 segments. The images were retrospectively and independently evaluated by two specialized radiologists who were blinded to the patient dose groups. All studies were assessed for overall image quality and the degree of contaminating venous enhancement. Each arterial segment was scored for the quality of vessel definition, the severity of stenoses, and the presence of collateral vessels. More than 99% of arterial segments were found to be of diagnostic image quality by both readers in all dose groups. Generalized estimating equation analysis showed a significant difference among the three groups with regard to vessel definition (P = .019). No significant difference was found between the high- and intermediate-dose groups; however, the low-dose group had significantly better vessel definition compared with the high-dose (P = .034) and intermediate-dose (P = .015) groups. There was no significant difference among the groups in visualization of collateral vessels. Venous contamination was seen less frequently in the low-dose group, but the difference did not achieve significance. The study showed that, compared with widely used dose strategies at 1.5 T, the contrast agent dose for 3.0-T lower extremity MR angiography can be reduced multifold without compromising image quality.

MR angiography of Adamkiewicz artery

Objective To prospectively investigate the feasibility of contrast material-enhanced magnetic resonance angiography(CE-MRA)for visualization of the spinal vasculature.Methods Ten volunteers and fifteen patients with thoracic or lumbar disk herniation underwent contrast-enhanced MR angiography of the thoracoabdominal aorta and posterior branches.Examination Was performed with three-dimensional CE-MRA technique and 0.3 mmol/kg of gadolinium contrast agent Was administrated.Results In all examinations,the Adamkiewicz artery,the anterior spinal artery(ASA),and their connections witll the aorta were identified.The Adamkiewicz artery originated between T8 and L3 in all examinations and derived from the left side of the aorta in 80% of all examinations.ASA was able to be observed from T6 to L3.The diameter of Adamkiewicz artery Was 0.6-1.2 mm and ASA was 0.6-1.0 mm.Conclusion CE-MRA Can be used to lOCalize Adamkiewicz artery and provide accurate information for clinical approach. Key words: Magnetic resonance imaging; Spinal cord; Adamkiewicz artery

Renal Artery Stenosis Evaluation: Diagnostic Performance of Gadobenate Dimeglumine–enhanced MR Angiography—Comparison with DSA

To prospectively determine diagnostic performance and safety of contrast material-enhanced (CE) magnetic resonance (MR) angiography with 0.1 mmol per kilogram of body weight gadobenate dimeglumine for depiction of significant steno-occlusive disease (> or =51% stenosis) of renal arteries, with digital subtraction angiography (DSA) as reference standard. This multicenter study was approved by local institutional review boards; all patients provided written informed consent. Patient enrollment and examination at centers in the United States complied with HIPAA. Two hundred ninety-three patients (154 men, 139 women; mean age, 61.0 years) with severe hypertension (82.2%), progressive renal failure (11.3%), and suspected renal artery stenosis (6.5%) underwent CE MR angiography with three-dimensional spoiled gradient-echo sequences after administration of 0.1 mmol/kg gadobenate dimeglumine at 2 mL/sec. Anteroposterior and oblique DSA was performed in 268 (91.5%) patients. Three independent blinded reviewers evaluated CE MR angiographic images. Sensitivity, specificity, and accuracy of CE MR angiography for detection of significant steno-occlusive disease (> or =51% vessel lumen narrowing) were determined at segment (main renal artery) and patient levels. Positive and negative predictive values and positive and negative likelihood ratios were determined. Interobserver agreement was analyzed with generalized kappa statistics. A safety evaluation (clinical examination, electrocardiogram, blood and urine analysis, monitoring for adverse events) was performed. Of 268 patients, 178 who were evaluated with MR angiography and DSA had significant steno-occlusive disease of renal arteries at DSA. Sensitivity, specificity, and accuracy of CE MR angiography for detection of 51% or greater stenosis or occlusion were 60.1%-84.1%, 89.4%-94.7%, and 80.4%-86.9%, respectively, at segment level. Similar values were obtained for predictive values and for patient-level analyses. Few CE MR angiographic examinations (1.9%-2.8%) were technically inadequate. Interobserver agreement for detection of significant steno-occlusive disease was good (79.9% agreement; kappa = 0.69). No safety concerns were noted. CE MR angiography performed with 0.1 mmol/kg gadobenate dimeglumine, compared with DSA, is safe and provides good sensitivity, specificity, and accuracy for detection of significant renal artery steno-occlusive disease.

Renal Artery Assessment with Nonenhanced Steady-State Free Precession versus Contrast-enhanced MR Angiography

To prospectively assess the diagnostic accuracy of nonenhanced three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography for detection of renal artery stenosis (RAS), with breath-hold contrast material-enhanced MR angiography performed as the reference standard. The study was local ethics committee approved; all patients gave written informed consent. Fifty-three patients (30 male, 23 female; mean age, 58 years) with arterial hypertension and suspected of having RAS were examined with 1.5-T 3D SSFP renal MR angiography. Stenosis grade, maximal visible vessel length, and subjective image quality were compared. Sensitivity, specificity, accuracy, and negative predictive value (NPV) were calculated on artery-by-artery and patient-by-patient bases. The significance of the results was assessed with the paired two-sided t test for continuous variables and with the marginal homogeneity test for categorical variables. Cohen kappa statistics were used to estimate interobserver agreement. One hundred eight renal arteries with 20 significant (>or=50%) stenoses were detected with contrast-enhanced MR angiography. At artery-by-artery analysis, sensitivity, specificity, accuracy, and NPV of nonenhanced SSFP MR angiography for RAS detection were 100%, 93%, 94%, and 100%, respectively, for observer 1 and 95%, 95%, 95%, and 99%, respectively, for observer 2. Corresponding patient-by-patient values were 100%, 92%, 94%, and 100%, respectively, for observer 1 and 100%, 95%, 96%, and 100%, respectively, for observer 2. Overestimation of stenosis grade with SSFP MR angiography resulted in six and four false-positive findings for readers 1 and 2, respectively. Mean maximal visible lengths of the renal arteries were 69.9 mm at contrast-enhanced MR angiography and 61.1 mm at SSFP MR angiography (P<.001). Both techniques yielded good to excellent image quality. Slab-selective inversion-prepared 3D SSFP MR angiography had high sensitivity, specificity, accuracy, and NPV for RAS detection, without the need for contrast material. However, RAS severity was overestimated in some patients.

Renal Arteries: Comparison of Steady-State Free Precession MR Angiography and Contrast-enhanced MR Angiography

All participants provided informed consent to participate in this study, which was approved by the institutional review board. Breath-hold three-dimensional (3D) steady-state free precession (SSFP) magnetic resonance (MR) angiography was compared with 3D contrast material-enhanced MR angiography in patients suspected of having renal artery stenosis. Two radiologists assessed visualization of renal arteries and detection of vascular disease. With SSFP MR angiography, 39 of 41 renal arteries in 19 patients were correctly detected. Relevant stenoses were correctly identified with SSFP MR angiography in two patients. In two patients, SSFP MR angiographic data sets led to false-positive overgrading of vascular disease. Fast breath-hold 3D SSFP MR angiography appears to be feasible for MR angiography of renal arteries.

Cardiac MR Imaging and MR Angiography for Assessment of Complex Tetralogy of Fallot and Pulmonary Atresia

Breath-hold electrocardiographically gated cardiac magnetic resonance (MR) imaging and contrast material-enhanced MR angiography are emerging as ideal techniques for the evaluation of complex congenital heart disease. Tetralogy of Fallot is the most common cause of cyanotic congenital heart disease and, in its classic form, is associated with varying degrees of hypoplasia of the central and peripheral pulmonary arteries, with valvar pulmonary atresia and collateral aortopulmonary vessels occupying the extreme end of the spectrum. Accurate assessment of the size and anatomy of the pulmonary arteries is often difficult with echocardiography and conventional cineangiography. Compared with echocardiography in particular, cardiac MR imaging with three-dimensional reconstruction has distinct advantages for pre- or postoperative assessment of pulmonary anatomy in patients with tetralogy of Fallot and pulmonary atresia. MR imaging enables the clear and complete depiction of anatomy and thus can provide additional information about pulmonary artery abnormalities that are difficult to evaluate with conventional cardiac imaging techniques.

Catheter Visualization with Resonant Markers at MR Imaging–guided Deployment of Endovascular Stents in Swine

To evaluate resonant circuits as markers for magnetic resonance (MR) imaging-guided placement of nitinol stents. The study was approved by the institutional animal research committee and complied with National Institutes of Health guidelines for care and use of laboratory animals. Resonant circuits similar to catheter markers used at conventional angiography were placed proximally and distally to a nitinol stent in a stent delivery system. Resonant circuits were tested in vitro and in vivo for signal intensity levels that would enable visualization during MR imaging-guided stent deployment. Experiments were conducted by using real-time imaging with a 1.5-T unit. Stents (n = 9) were deployed in the vena cava (n = 2), abdominal aorta (n = 2), isthmus of the aorta (n = 2), and carotid (n = 2) and iliac (n = 1) arteries in five pigs. After intervention, the site of the stent was investigated with balanced fast field-echo MR imaging and contrast material-enhanced MR angiography. Blood flow velocities were measured in the stent lumen and next to the stent with velocity-encoded cine MR imaging. Level of agreement was determined with Bland-Altman analysis. During all interventions, resonant circuits provided highly visible MR signal that allowed fast and reliable visualization of the stent delivery system. Borders of loaded stents were clearly marked, which allowed precise stent placement in all experiments. Balanced fast field-echo MR imaging and contrast-enhanced MR angiography provided information about immediate postintervention position. Positions depicted on MR images were found accurate at postmortem examination. Results of Bland-Altman analysis showed good agreement between blood flow velocities measured in and next to the stent lumen, with a mean difference of -9 cm/sec +/- 5 (standard deviation). Resonant circuits are well suited for use at deployment of endovascular stents.

Heart failure: evaluation of cardiopulmonary transit times with time-resolved MR angiography.

To measure cardiopulmonary transit times in patients with heart failure by using low-dose, time-resolved magnetic resonance (MR) angiography and to determine if transit curves reflect conventional MR indexes of cardiac function. Twenty-six patients with heart failure and left ventricular (LV) systolic dysfunction (17 men and nine women; age range, 22-78 years) and thirteen control subjects (eight men and five women; age range, 23-59 years) were examined with MR imaging. The examination consisted of rapid cine MR imaging throughout the heart, followed by contrast material-enhanced time-resolved three-dimensional MR angiography of the cardiac chambers and pulmonary vasculature. Time-intensity curves for the pulmonary artery and ascending aorta were derived from the MR angiography images. Cardiopulmonary transit times and dispersions (full widths at half maximum [FWHM]) were determined from the curves. Transit times and FWHM values for the patients with heart failure were compared with control values by using two-tailed t tests, and transit time was correlated with standard LV functional parameters calculated from the cine MR images. Cardiopulmonary transit times and FWHM values were significantly prolonged in the patients with heart failure compared with those in the control patients (P <.001). Transit time correlated directly with LV end-diastolic and end-systolic volumes and inversely with LV ejection fraction (R > 0.60). However, transit time did not correlate strongly with age, body surface area, heart rate, LV mass, stroke volume, cardiac output, or sphericity index. Time-resolved MR angiography allows determination of cardiopulmonary transit times that are significantly prolonged in heart failure and correlate directly with LV volumes and inversely with LV ejection fraction.

From the RSNA refresher courses: MR imaging of aortic and peripheral vascular disease.

Acquired diseases of the aorta and peripheral arteries are common. Owing to technical advances, magnetic resonance (MR) angiography has become the primary imaging modality for assessment of aortic and peripheral arterial disease. Contrast material-enhanced MR angiography is a rapid and robust technique that has emerged as the principal MR angiographic technique for evaluation of vascular disease. Two-dimensional time-of-flight MR angiography still has some well-validated applications, especially in distal peripheral vascular disease. Phase-contrast flow imaging is an important technique for quantification of blood flow. Black-blood imaging is a valuable tool for evaluation of the vessel wall. Understanding the principles of the main MR angiographic techniques is essential for consistent acquisition of diagnostic images. In addition, tailoring the acquisition parameters and the imaging protocol to the vessel being imaged and the clinical question is mandatory for optimal results. Future technical developments that will lead to faster image acquisition and better contrast agents promise to further improve image quality.