The objective of this study was to assess the feasibility of carotid vessel wall imaging at 7.0 for T magnetic resonance imaging (MRI) in a series of patients with a symptomatic greater than 70% ...stenosis of the internal carotid artery.
First, a series of 6 healthy volunteers were scanned at 3.0 T and 7.0 T MRI to perform a signal-to-noise ratio comparison between these 2 field strengths. Second, in patients with a greater than 70% stenosed carotid artery, a 7.0 T MRI protocol, consisting of a dual-echo turbo spin echo sequence (echo times of 45 and 150 milliseconds) and a T1-weighted turbo spin echo sequence, was obtained. Lumen and vessel wall were delineated for interobserver and intraobserver reproducibility, and signal intensity distribution in the most severely stenosed part of the internal carotid artery was correlated with different plaque components on histopathologic findings.
The mean (SD) signal-to-noise ratio in the vessel wall was 42 (12) at 7.0 T and 24 (4) at 3.0 T. Nineteen patients were included, but technical issues yielded carotid MRI data of 14 patients available for the final analysis. Of these patients, 4 were diagnosed with stroke, 7 were diagnosed with a transient ischemic attack, and 3 were diagnosed with amaurosis fugax. Intraclass correlation coefficient of the agreements of lumen and vessel wall determination between 2 observers and between the repeated measures of 1 observer were above 0.80 in both 3.0 T and 7.0 T data sets of the healthy volunteers and also in the 7.0 T data set of the patients. Signal hyperintensity in the 7.0 T magnetic resonance images was inversely proportional to calcification. Other correlations between plaque components and signal intensity could not be confirmed.
This first series of patients with carotid atherosclerotic plaque who were scanned at 7.0 T MRI shows that 7.0 T MRI enables to adequately determine lumen and vessel wall areas. Signal hyperintensity in these 7.0 T magnetic resonance images was inversely proportional to calcification. However, at this stage, no other correlations between histologic findings and vessel wall contrast were found. Implementation of in vivo high-resolution 7.0 T MRI of plaque components for risk stratification remains challenging. Future development of hardware and software is still needed to attain a more robust setup and to enable complete plaque characterization, similar to what is currently possible with multiple MRI sequences at 1.5 T and 3.0 T MRI.
Constrictive vascular remodeling (VR) is the most significant component of restenosis after balloon angioplasty (PTA). Whereas in physiological conditions VR is associated with normalization of shear ...stress (SS) and wall stress (WS), after PTA the role of SS and WS in VR is unknown. Furthermore, whereas matrix metalloproteinase inhibition (MMPI) has been shown to modulate VR after PTA, its effect on the SS and WS control mechanisms after PTA is unknown.
PTA was performed in external iliac arteries of 12 atherosclerotic Yucatan pigs, of which 6 pigs (7 vessels) received the MMPI batimastat and 6 pigs (10 vessels) served as controls. Before and after the intervention and at 6-week follow-up, intravascular ultrasound pullback was performed, allowing 3D reconstruction of the treated segment and computational fluid dynamics to calculate the media-bounded area and SS. WS was derived from the Laplace formula. Immediately after PTA, media-bounded area, WS, and SS changed by 20%, 16%, and -49%, respectively, in both groups. VR was predicted by SS and WS. In the control group, SS and WS had been normalized at follow-up with respect to the reference segment. In contrast, for the batimastat group, the SS had been normalized, but not the WS. The latter is attributed to an increase in wall area at follow-up.
Vascular remodeling after PTA is controlled by both SS and WS. MMPI inhibited the WS control system.
PDF
