MR angiography of lower-extremity arterial disease: preliminary experience.

Nineteen patients underwent magnetic resonance (MR) angiography for evaluation of lower-extremity arterial disease. The underlying conditions included atherosclerotic occlusive disease in 12 patients, femoral or popliteal aneurysms in four, and bypass graft stenoses or occlusion in four. In the patients with occlusive disease, the iliac and femoropopliteal vessels were classified as patent, moderately stenotic, severely stenotic, or occluded. Fifteen of 16 occlusions (accuracy = 94%) were correctly classified. In the one missed case, there was a long delay between MR angiography and x-ray angiography and it is likely that the occlusion occurred during the interval. Three of five severe stenoses were correctly classified with MR angiography. In two cases of iliac artery stenosis, there was a signal void at the point of maximal stenosis, which on the basis of anatomic features could be recognized as severe stenosis rather than an occlusion. Three of four moderate stenoses were correctly classified. Correlation with x-ray angiography or surgery demonstrated the ability of MR angiography to accurately depict the status of runoff vessels.     

Renal artery stenosis: evaluation with conventional angiography versus gadolinium-enhanced MR angiography

PURPOSE: To evaluate the interobserver and intermodality variability of conventional angiography and gadolinium-enhanced magnetic resonance (MR) angiography in the assessment of renal artery stenosis. MATERIALS AND METHODS: Fifty-four patients underwent conventional angiography and gadolinium-enhanced three-dimensional gradient-echo MR angiography. Three angiographers blinded to each other's interpretations and the MR angiographic findings assessed the conventional angiograms for renal artery stenosis. Similarly, three blinded MR imagers evaluated the MR angiograms. RESULTS: Interobserver variability for the degree of renal artery stenosis in the 107 kidneys evaluated was not significantly different between the two modalities. The mean SD of the degree of stenosis was 6.9% at MR angiography versus 7.5% at conventional angiography (alpha < or = .05, P > .05). In 70 kidneys (65%), the average degree of stenosis reported by the readers for the two modalities differed by 10% or less. In 22 cases (21%), the degree of stenosis was overestimated with MR angiography by more than 10% relative to the results of conventional angiography. In 15 cases (14%), the degree of stenosis was underestimated with MR angiography by more than 10%. CONCLUSION: Gadolinium-enhanced MR angiography permits evaluation of renal artery stenosis with an interobserver variability comparable with that of conventional angiography.     

Peripheral arterial disease: sensitivity-encoded multiposition MR angiography compared with intraarterial angiography and conventional multiposition MR angiography

A sensitivity-encoded magnetic resonance (MR) angiography protocol was developed in which imaging times in the pelvic and upper-leg positions were reduced and isotropic submillimeter voxel volumes were acquired in the lower-leg position. To achieve this, sensitivity encoding and random central-k-space segmentation in a centric filling order were applied. Results with this technique were compared with those with midstream aortic digital subtraction angiography (DSA) (as the reference standard) and conventional MR angiography in 15 patients with peripheral vascular disease. The results show that sensitivity-encoded MR angiography demonstrates increased diagnostic accuracy in comparison to that with conventional MR angiography and depicts more open infragenual arterial segments compared with both midstream aortic DSA and conventional MR angiography.     

Aortic aneurysmal disease: assessment of stent-graft treatment-CT versus conventional angiography

PURPOSE: To compare computed tomographic (CT) angiography and conventional angiography for determining the success of endoluminal stent-graft treatment of aortic aneurysms. MATERIALS AND METHODS: Forty patients underwent conventional angiography and CT angiography following treatment of aortoiliac aneurysms with endoluminal stent-grafts. Six additional sets of conventional angiographic-CT angiographic examinations were performed in five patients after placement of additional stent-grafts or coil embolization to treat perigraft leakage. Three faculty CT radiologists who were blinded to patient clinical data and outcome independently interpreted the CT angiograms, and three faculty angiographers, who were not involved in the stent-graft deployment, interpreted the conventional angiograms. Images were assessed for the presence of postdeployment complications. A reference standard was developed by experienced radiologists using all available images and clinical data. Sensitivities, specificities, and kappa values were calculated. RESULTS: Perigraft leakage was the most commonly identified complication. Twenty perigraft leaks were detected in the results of 46 examinations. Sensitivities and specificities for detecting perigraft leakage were 63% and 77% for conventional angiography and 92% and 90% for CT angiography, respectively. The kappa value was 0. 41 for conventional angiography and 0.81 for CT angiography. CONCLUSION: CT angiography is the preferred method for establishing the presence of perigraft leakage following treatment of aortoiliac aneurysms with stent-grafts.     

Peripheral arterial occlusive disease: prospective comparison of MR angiography and color duplex US with conventional angiography

Conventional angiography, two-dimensional inflow magnetic resonance (MR) angiography, and color duplex ultrasound (US) were performed on 12 patients in a blinded, prospective study. The ability to grade arterial lesions and plan revascularization interventions were compared. Arterial lesions were categorized as nonsignificant (0%-49% diameter reduction) or significant (50%-100% diameter reduction). Determination of nonsignificant and significant lesions with MR angiography was in agreement with that at conventional angiography in 100 of 140 lesions (71%). Agreement between results of conventional angiography and color duplex US occurred with 114 of 123 infrainguinal lesions (93%). Twenty-one vascular interventions were planned by using conventional angiography; there was agreement with color duplex US in 11 cases and MR angiography in five. Color duplex US performed well in the assessment of infrainguinal disease but was limited in the evaluation of iliac segments because of nonvisualization. The iliac region was visualized in more patients with MR angiography than with color duplex US, but image quality with MR angiography was inconsistent. Strategies to improve MR angiography of the peripheral vasculature merit further study.     

Diabetes and peripheral arterial occlusive disease: prospective comparison of contrast-enhanced three-dimensional MR angiography with conventional digital subtraction angiography

OBJECTIVE: The purpose of this study was to compare contrast-enhanced three-dimensional MR angiography with conventional digital subtraction angiography (DSA) for identifying and evaluating arteries of the distal calf and foot in diabetic patients with severe arterial occlusive disease who will undergo distal bypass surgery. SUBJECTS AND METHODS: Twenty-four feet of 24 consecutive patients with diabetes and limb-threatening lower extremity ischemia were prospectively imaged using an ultrafast three-dimensional fast low-angle shot sequence on a 1.5-T MR scanner. All patients also underwent DSA of the diseased extremity within 5 days. Images were interpreted in a randomized manner by two observers in conference. Each lower extremity was divided into seven potential arterial segments. Image analysis included the detection of patent, stenosed, or occluded vessel segments. A vascular surgeon formulated treatment plans on the basis of findings from DSA and then formulated treatment plans on the basis of findings from both DSA and MR angiography. RESULTS: MR angiography was significantly better than DSA in revealing peripheral runoff vessels (p < 0.001). In nine (38%) of the 24 patients, MR angiography showed patent pedal vessels suitable for distal bypass grafting that were not revealed by DSA. Because of the results of MR angiography, treatment plans changed in seven of the nine patients in whom patent vessels were subsequently used as target vessels for distal pedal bypass grafts. CONCLUSION: Contrast-enhanced three-dimensional MR angiography is superior to DSA in revealing patent vessel segments of the foot in diabetic patients with severe arterial occlusive disease. Contrast-enhanced three-dimensional MR angiography should be part of the diagnostic algorithm for patients in whom pedal bypass grafting is a therapeutic option.     

Aortic stenosis: evaluation with multidetector CT angiography and MR imaging

Aortic valvular stenosis (AS) is the most common valve disease which results in the need for a valve replacement. Although a Doppler echocardiography is the current reference imaging method, the multidetector computerized tomograpghy (MDCT) and magnetic resonance imaging (MRI) have recently emerged as a promising method for noninvasive valve imaging. In this study, we briefly describe the usefulness and comparative merits of the MDCT and MRI for the evaluation of AS in terms of valvular morphology (as the causes of AS), quantification of aortic valve area, pressure gradient of flow (for assessment severity of AS), and the evaluation of the ascending aorta and cardiac function (as the secondary effects of AS). The familiarity with the MDCT and MRI features of AS is considered to be helpful for the accurate diagnosis and proper management of patients with a poor acoustic window.     

Peripheral arterial disease: gadolinium-enhanced MR angiography versus color-guided duplex US--a meta-analysis

PURPOSE: To summarize and compare the published data on gadolinium-enhanced magnetic resonance (MR) angiography and color-guided duplex ultrasonography (US) for the work-up for peripheral arterial disease. MATERIALS AND METHODS: Studies published between January 1984 and November 1998 were included if (a) gadolinium-enhanced MR angiography and/or color-guided duplex US were performed for evaluation of arterial stenoses and occlusions in the work-up for peripheral arterial disease of the lower extremities, (b) conventional angiography was the reference standard, and (c) absolute numbers of true-positive, false-negative, true-negative, and false-positive results were available or derivable. RESULTS: With a random effects model, pooled sensitivity for MR angiography (97.5% [95% CI: 95.7%, 99.3%]) was higher than that for duplex US (87.6% [95% CI: 84.4%, 90.8%]). Pooled specificities were similar: 96.2% (95% CI: 94.4%, 97.9%) for MR angiography and 94.7% (95% CI: 93.2%, 96.2%) for duplex US. Summary receiver operating characteristic analysis demonstrated better discriminatory power for MR angiography than for duplex US. Regression coefficients for MR angiography versus US were 1.67 (95% CI: -0.23, 3.56) with adjustment for covariates, 2.11 (95% CI: 0.12, 4.09) without such adjustment, and 1.73 (95% CI: 0.44, 3.02) with a random effects model. CONCLUSION: Gadolinium-enhanced MR angiography has better discriminatory power than does color-guided duplex US and is a highly sensitive and specific method, as compared with conventional angiography, for the work-up for peripheral arterial disease.     

Assessment of aortoiliac and renal arteries: MR angiography with parallel acquisition versus conventional MR angiography and digital subtraction angiography

PURPOSE: To prospectively compare the image quality, sensitivity, and specificity of three-dimensional gadolinium-enhanced magnetic resonance (MR) angiography accelerated by parallel acquisition (ie, fast MR angiography) with MR angiography not accelerated by parallel acquisition (ie, conventional MR angiography) for assessment of aortoiliac and renal arteries, with digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: The study was approved by the institutional review board; informed consent was obtained from all patients. Forty consecutive patients (33 men, seven women; mean age, 63 years) suspected of having aortoiliac and renal arterial stenoses and thus examined with DSA underwent both fast (mean imaging time, 17 seconds) and conventional (mean imaging time, 29 seconds) MR angiography. The arterial tree was divided into segments for image analysis. Two readers independently evaluated all MR angiograms for image quality, presence of arterial stenosis, and renal arterial variants. Image quality, sensitivity, and specificity were analyzed on per-patient and per-segment bases for multiple comparisons (with Bonferroni correction) and for dependencies between segments (with patient as the primary sample unit). Interobserver agreement was evaluated by using kappa statistics. RESULTS: Overall, the image quality with fast MR angiography was significantly better (P=.001) than that with conventional MR angiography. At per-segment analysis, the image quality of fast MR angiograms of the distal renal artery tended to be better than that of conventional MR angiograms of these vessels. Differences in sensitivity for the detection of arterial stenosis between the two MR angiography techniques were not significant for either reader. Interobserver agreement in the detection of variant renal artery anatomy was excellent with both conventional and fast MR angiography (kappa=1.00). CONCLUSION: Fast MR angiography and conventional MR angiography do not differ significantly in terms of arterial stenosis grading or renal arterial variant detection.     

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.     

外周动脉闭塞性疾病:评估高空间和时间分辨率并低剂量钆对比剂的3 T MR检查方案及与传统血管造影比较

目的评估一种3T外周性MR血管成像(MRA)检查方案,对小腿部位联合应用了连续床进(CTM)全血流MRA检查与时间分辨(TWIST)MRA检查,对比剂总量为     

Imaging of aortoiliac arterial disease. Duplex ultrasound and MR angiography versus digital subtraction angiography

Purpose: To evaluate and compare the diagnostic accuracy of duplex ultrasound (US) and MR angiography (MRA) at 1.0 T in aortoiliac arterial disease using digital subtraction angiography (DSA) as the reference standard. In addition, a comparison of the 2D time-of flight (TOF) and 3D contrast-enhanced MRA (CE MRA) techniques was performed.Material and Methods: Prospectively, 39 patients with symptoms of lower-extremity arterial occlusive disease were examined using US, TOF MRA, CE MRA and DSA. Significant lesions (stenosis ≥50%) and occlusions were evaluated blindly for each method.Results: For all segments, the sensitivity for US, TOF MRA and CE MRA with regard to significant lesions was 0.72, 0.81 and 0.81, respectively, and the specificity for each was 0.97, 0.91 and 0.92, respectively. For significant lesions above the inguinal ligament the corresponding sensitivity was 0.84, 0.89 and 0.94 and the specificity 0.93, 0.82 and 0.73, respectively. The specificity was higher when the two MRA methods were combined. TOF MRA overgraded 7 segments as occluded. In most cases, the length of the occlusions was correctly determined on CE MRA, overestimated on TOF MRA and uncertain on US.Conclusion: Neither US nor MRA were sufficiently accurate to fully replace angiography. MRA was preferable to US as a non-invasive test when vascular intervention was contemplated. Although CE MRA was superior to TOF MRA, the most accurate results were achieved when the two methods were combined.     

Peripheral arterial disease. Contrast-enhanced 3D MR angiography of the lower leg and foot compared with conventional angiography

PURPOSE: To determine whether contrast-enhanced 3D MR angiography (CE MRA) could replace digital subtraction angiography (DSA) for the evaluation of atherosclerotic peripheral vascular disease of the lower leg and foot. MATERIAL AND METHODS: Thirty-five patients with symptoms of atherosclerotic disease of the leg were examined prospectively with CE MRA of the foot and the lower legs as well as with DSA from the aorta to the pedal arches. The MRA technique was focused on optimal imaging of the arteries of the foot. RESULTS: The agreement between CE MRA and DSA for grading of stenosis was moderate to good (weighted kappa-values 0.48-0.80). The sensitivity of CE MRA for detection of significant stenosis (> or = 50%) was 92% and the specificity was 64% with DSA as gold standard. CONCLUSION: CE MRA is a fairly accurate method for the demonstration of atherosclerotic disease below the knee including the pedal arches. It can replace DSA for the assessment of distal arteries in patients with impaired renal function. However, image quality and resolution still needs to be improved before CE MRA can become the method of choice in all patients.