High-resolution MR Imaging of Human Atherosclerotic Femoral Arteries In Vivo: Validation with Intravascular Ultrasound - ScienceDirect

Journal of Vascular and Interventional Radiology

Volume 14, Issue 2, Part 1, February 2003, Pages 227-231

Journal of Vascular and Interventional Radiology

https://doi.org/10.1097/01.RVI.0000058325.82956.63 Get rights and content

PURPOSE

To establish a magnetic resonance (MR) imaging protocol for noninvasive in-vivo analysis of atherosclerotic femoral artery segments in humans and to compare the results to those of intravascular ultrasonography (IVUS).

MATERIALS AND METHODS

In seven patients with peripheral arterial occlusive disease, 20 femoral arterial segments per person were examined by high-resolution (HR) MR imaging and IVUS. Comparison was possible in 123 of 140 segments. MR imaging was performed at 1.5 T with use of a three-dimensional (3D) time-of-flight sequence with an in-plane resolution of 0.78 × 0.49 mm². 3D contrast-enhanced MR angiography was used for exact positioning of the HR MR imaging slices. IVUS (3.5 F, 40 MHz) was performed with use of a motorized pullback system. Parameters analyzed included cross-sectional lumen area (LA), vessel area (VA), and extent of vessel wall calcification.

RESULTS

Agreement between IVUS and HR MR imaging was analyzed with use of the Bland-Altman method. The paired LA measurements were in close agreement: the Bland-Altman mean bias in LA was −0.4 mm with a precision of ± 5.1 mm (P = .062). As a result of dorsal echo extinction in IVUS, VA measurements were feasible in only 74 of 140 segments. VA measurements were moderately correlated (r = 0.74;P < .0001), and a 25% overestimation by HR MR imaging compared to IVUS was observed. Intraand interobserver comparisons for LA and VA measured with HR MR imaging did not show significant differences. Vessel wall calcifications were classified with a sensitivity of 91%, a specificity of 93%, and an accuracy of 93%.

CONCLUSIONS

The MR imaging protocol introduced in the present study permits precise assessment of LA and extent of calcification in peripheral arterial occlusive disease in vivo. HR MR imaging shows high concordance with IVUS and may have the potential for noninvasive therapy monitoring.

Section snippets

MATERIALS AND METHODS

Included in the study were seven consecutive patients (six men; mean age, 60.0 y ± 6) scheduled for balloon angioplasty of a short (≤1 cm) denovo stenosis of the superficial femoral artery. The stenosis was localized with use of duplex US, quantified, and its position marked on the overlying skin to ensure exact MR imaging coil placement. Patients were examined with use of HR MR imaging a maximum of 15 hours before intervention. The study protocol was approved by the institutional ethics review

RESULTS

A total of 140 corresponding segments were assessed by IVUS and HR MR imaging. Seventeen segments did not provide sufficient flow signal intensity because of a proximal highgrade stenosis. Therefore, the analysis comprised 123 of 140 segments (88%). The mean LAs measured by IVUS and HR MR imaging were 17.6 mm² ± 5.8 and 17.1 mm² ± 6.0, respectively, with a resulting coefficient of correlation (r) of 0.90 (P < .001). The paired LA measurements closely agreed: Bland-Altman analysis revealed a

DISCUSSION

In the present study, we compared HR MR imaging with IVUS in the quantification of atherosclerotic vessel segments in superficial femoral arteries in man. Results document HR MR imaging's capability to exactly measure lumen parameters and reliably quantify vessel wall calcifications by the use of high-resolution coil systems. HR MR imaging measurements showed a low level of intraand interobserver variability for lumen and vessel dimensions.

In most studies published to date validating MR imaging

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Histology confirmed plaques in human specimens, with calcifications appearing as signal voids. Mean FCT agreed with histological measurements within 13% on average (correlation coefficient, R = 0.98; Bland-Altman analysis, -1.3 ± 68.9 μm). In vivo aortic wall and plaque size measured by 80 μm intravascular CMR agreed with histology.
Intravascular 3T CMR with loopless detectors can both locate atherosclerotic lesions, and accurately measure FCT at high-resolution in a strategy that appears feasible in vivo. The approach shows promise for quantifying vulnerable plaque for evaluating experimental therapies.
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Fast, minimally invasive, high-resolution intravascular imaging is essential for identifying vascular pathological features and for developing novel diagnostic tools and treatments. Intravascular magnetic resonance imaging (MRI) with active internal probes offers high sensitivity to pathological features without ionizing radiation or the limited luminal views of conventional X-rays, but has been unable to provide a high-speed, high-resolution, endoscopic view. Herein, real-time MRI endoscopy is introduced for performing MRI from a viewpoint intrinsically locked to a miniature active, internal transmitter–receiver in a clinical 3.0-T MRI scanner. Real-time MRI endoscopy at up to 2 frames/s depicts vascular wall morphological features, atherosclerosis, and calcification at 80 to 300 μm resolution during probe advancement through diseased human iliac artery specimens and atherosclerotic rabbit aortas in vivo. MRI endoscopy offers the potential for fast, minimally invasive, transluminal, high-resolution imaging of vascular disease on a common clinical platform suitable for evaluating and targeting atherosclerosis in both experimental and clinical settings.
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2008, Journal of Vascular and Interventional Radiology
Citation Excerpt :
MR imaging of the atherosclerotic vessel wall has been used to study several vessel regions, in particular the carotid artery and the aorta (4,5,13,14,28). Comparison with surgical carotid specimens or intravascular US scans showed that plaque size can be accurately measured with MR imaging (2,28,29). A number of MR imaging studies have shown that the descending thoracic aorta is a favorable vessel segment for quantitative assessment of vessel wall area and thickness for several reasons: (a) there is significant atherosclerotic wall change, (b) the segment is responsive to statin treatment, and (c) quantitative measurements are highly reproducible (13–15,30).
To compare the aortic plaque burden in patients with heterozygous familial hypercholesterolemia on long-term statin treatment with that of matched control subjects.
The authors studied 11 heterozygous, nonsmoking, nondiabetic, and nonhypertensive patients with familial hypercholesterolemia (mean age, 44 years ± 10) who had been receiving cholesterol-lowering management for a mean of 12 years ± 5, including 8.25 years ± 4.24 with the highest tolerable doses of a statin (or a statin plus ezetimibe), and 26 age- and sex-matched control subjects with 3T magnetic resonance (MR) imaging of the descending thoracic aorta by using an axial T2-weighted turbo spin-echo sequence.
Quantitative analysis demonstrated that the aortic vessel wall area was significantly larger in patients with familial hypercholesterolemia than in control subjects (123 mm² ± 23 vs 102 mm² ± 18, respectively; P < .007), as was vessel wall thickness (1.63 mm ± 0.28 vs 1.37 mm ± 0.16, respectively; P < .001). No significant difference was found between mean values of routine serum lipid and lipoprotein parameters.
The results of this preliminary study show that patients with heterozygous familial hypercholesterolemia have a higher aortic atherosclerotic plaque burden than control subjects at quantitative MR imaging despite long-term lipid-lowering therapy. This information may help design future studies evaluating plaque burden and cardiovascular risk.
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In vivo high resolution MR imaging has been validated in human atherosclerotic femoral arteries with intravascular ultrasound (IVUS). MRI showed high concordance with IVUS for assessment of lumen area, vessel wall dimensions and vascular calcifications.17 We recently reported the effects of PTA and PTA+EVBT at 24-hours and 3-months follow-up in the same group of patients.3
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The effects of both procedures on vessel wall at 24-hours and 3-months have been reported. Despite similar percent decrease in lumen area between 3- and 24-months in both groups (−8% for PTA and −11% for PTA+EVBT), at 24-months lumen area gain compared to baseline was +30% in PTA versus +82% in PTA+EVBT (p < 0.05). Total vessel area, which was increased at 24-hours and 3-months, returned to pre-treatment value in both groups.
We demonstrated non-invasively that restenosis and inward remodeling after PTA are delayed by EVBT. At 24-months, patients treated with brachytherapy have larger lumen than those treated with PTA alone. The decrease in luminal and total vessel area between 3- and 24-months after EVBT indicates that the restenotic and remodeling process is not abolished but delayed with this therapy.
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: None of the other authors has identified a potential conflict of interest.

Copyright © 2003 Society of Interventional Radiology. Published by Elsevier Inc. All rights reserved.