Although the ability of MRI to investigate carotid plaque composition is well established, the mechanism and the significance of plaque gadolinium (Gd) enhancement remain unknown. We evaluated ...clinical and histological significance of Gd enhancement of carotid plaque in patients undergoing endarterectomy for carotid stenosis.
Sixty-nine patients scheduled for a carotid endarterectomy prospectively underwent a 3-T MRI. Carotid plaque enhancement was assessed on T1-weighted images performed before and 5 minutes after Gd injection. Enhancement was recorded according to its localization. Histological analysis was performed of the entire plaque and of the area with matched contrast enhancement on MR images.
Gd enhancement was observed in 59% patients. Three types of carotid plaques were identified depending on enhancement location (shoulder region, shoulder and fibrous cap, and central in the plaque). Fibrous cap rupture, intraplaque hemorrhage, and plaque Gd enhancement was significantly more frequent in symptomatic than in asymptomatic patients (P=0.043, P<0.0001, and P=0.034, respectively). After histological analysis, Gd enhancement was significantly associated with vulnerable plaque (American Heart Association VI, P=0.006), neovascularization (P<0.0001), macrophages (P=0.030), and loose fibrosis (P<0.0001). Prevalence of neovessels, macrophages, and loose fibrosis in the area of Gd enhancement was 97%, 87%, and 80%, respectively, and was different depending on the enhancement location in the plaque. Fibrous cap status and composition were different depending on the type of plaque.
Gd enhancement of carotid plaque is associated with vulnerable plaque phenotypes and related to an inflammatory process.
Atherosclerosis is a major cause of global morbidity and mortality that could benefit from novel targeted therapeutics. Recent studies have shown efficient and local drug delivery with nanoparticles, ...although the nanoparticle targeting mechanism for atherosclerosis has not yet been fully elucidated. Here we used in vivo and ex vivo multimodal imaging to examine permeability of the vessel wall and atherosclerotic plaque accumulation of fluorescently labeled liposomal nanoparticles in a rabbit model. We found a strong correlation between permeability as established by in vivo dynamic contrast enhanced magnetic resonance imaging and nanoparticle plaque accumulation with subsequent nanoparticle distribution throughout the vessel wall. These key observations will enable the development of nanotherapeutic strategies for atherosclerosis.
The endovascular technique is used in the first line treatment in many complex aortic pathologies. Its clinical outcome is mostly determined by the appropriate selection of a stent-graft for a ...specific patient and the operator's experience. New tools are still needed to assist practitioners with decision making before and during procedures. For this purpose, numerical simulation enables the digital reproduction of an endovascular intervention with various degrees of accuracy. In this review, we introduce the basic principles and discuss the current literature regarding the use of numerical simulation for endovascular management of complex aortic diseases. Further, we give the future direction of everyday clinical applications, showing that numerical simulation is about to revolutionize how we plan and carry out endovascular interventions.
Atherosclerotic plaque development in the arterial wall is the result of complex interaction between the wall's endothelial layer and blood hemodynamics. However, the interaction between hemodynamic ...parameters and inflammation in plaque evolution is not yet fully understood. The aim of the present study was to investigate the relation between wall shear stress (WSS) and vessel wall inflammation during atherosclerotic plaque development in a minipig model of carotid stenosis.
A surgical procedure was performed to create left common carotid artery stenosis by placement of a perivascular cuff in minipigs under atherogenic diet. Animals were followed up on 3T MRI, 1 week after surgery and 3, 6, and 8 months after initiation of the diet. Computational fluid dynamics simulation estimated WSS distribution for the first imaging point. Vascular geometries were co-registered for direct comparison of plaque development and features (Gadolinium- and USPIO-Contrast Enhanced MRI, for permeability and inflammation respectively) with the initial WSS. Histological analysis was performed and sections were matched to MR images, based on spatial landmarks.
Vessel wall thickening, permeability and inflammation were observed distally from the stenosis. They were eccentric and facing regions of normal wall thickness. Histological analysis confirmed eccentric plaque formation with lipid infiltration, intimal thickening and medial degradation. High phagocytic activity in the stenosis region was co-localized with high WSS, corresponding to intense medial degradation observed on histology samples.
Lower WSS promotes atherosclerotic plaque development distal to an induced stenosis. Vascular and perivascular inflammation locations were predominant in the high WSS stenosis segment, where medial thinning was the major consequence.
Objective Carotid magnetic resonance imaging (MRI) may be a useful tool in characterizing carotid plaque vulnerability, but large studies are still lacking. The purpose of this study was to assess ...carotid MRI features of vulnerable plaque in a large study and the changes in carotid plaque morphology with respect to time since the neurological event. Methods We included 161 patients with carotid plaque more than 3 mm thick. All patients underwent carotid MRI to obtain 3-T high-resolution magnetic resonance sequences. Large lipid core, intraplaque hemorrhage (IPH), fibrous cap rupture (FCR), and gadolinium enhancement (GE) were assessed and classified as present or absent. Prevalences of these features were then compared between symptomatic and asymptomatic patients and time since stroke. Results Seven patients were excluded because of poor image quality. Of the remaining 154 patients, 52 were symptomatic and 102 were asymptomatic. The prevalences of IPH (39 vs 16%; P = .002), FCR (30 vs 9%; P = .001), and GE (75 vs 55%; P = .015) were significantly higher in symptomatic than asymptomatic patients. After multivariate analysis, the prevalences of IPH (odds ratio, 2.6; P = .023) and FCR (odds ratio, 2.8; P = .038) were still significantly higher. The prevalence of IPH was significantly higher in symptomatic patients with plaque regardless of the time since the neurological event. For FCR, the difference between symptomatic and asymptomatic patients was significant only during the first 15 days after the neurological event. Conclusions Carotid MRI can identify plaque features that are associated with symptomatic presentation and may be indicative of plaque vulnerability. These features may ultimately be used in the management of extracranial carotid stenosis.
The overall performance of an electrostrictive polymer is rated by characteristic numbers, such as its transverse strain, blocking force, and energy density, which are clearly limited by several ...parameters. Besides the geometrical impact, intrinsic material parameters, such as the permittivity coefficient as well as the Young's modulus and the breakdown electric field, have strong influences on the actuation properties of an electroactive polymer and thus on the device's overall behavior. As a result, an analysis of the figures of merit (FOMs) involving all relevant material parameters for the transverse strain, the blocking force, and the energy density was carried out, making it possible to determine the choice of polymer matrix in order to achieve a high actuator performance. Another purpose of this work was to demonstrate the possibility of accurately measuring the free deflection without the application of an external force and inversely measuring the blocking force under quasi-static displacement. The experimental results show good electrostrictive characteristics of the plasticized terpolymer under relatively low electric fields.
To evaluate the efficacy of percutaneous transluminal angioplasty (PTA) of atherosclerotic lesions of the common femoral artery (CFA) and its bifurcation.
From 2009 to 2013, 53 patients (43 men, ...average age, 68 years) were included in a single-center, nonrandomized, prospective study. Indication was disabling intermittent claudication (n = 36) or chronic critical limb ischemia (n = 17). Thirty-four procedures (64%) were isolated CFA PTA, whereas 7 of 53 (13%) involved inflow (including 4 iliac occlusions) and 12 of 53 (23%) involved outflow vessels. Primary stenting was performed in 50 cases (95%). CFA occlusions were recanalized in 4 of 53. Lesions involved the bifurcation in 22 cases (40%). Follow-up consisted of clinical examination and duplex scanning with ankle-brachial index measurement at 1, 6, and 12 months. A biplane X-ray was performed at 1 year. The primary end point was the absence of binary restenosis (>50% reobstruction of the CFA). Secondary end points were freedom from target lesion revascularization (TLR) and stent fracture rate.
Procedural success was achieved in 96% of cases. At a mean follow-up of 24 months (with 1 patient lost of follow-up), the absence of binary restenosis was 92.5%. At the end of follow-up, 82% of patients continued to show clinical improvement. Freedom from TLR was 97%. Stent fracture rate at 1 year was 9%.
PTA of the CFA and its bifurcation is a reliable technique with good midterm functional results. These results justify performing a randomized study comparing surgery and endovascular treatment.
Previous studies have suggested the role of microcalcifications in plaque vulnerability. This exploratory study sought to assess the potential of hybrid positron-emission tomography (PET)/magnetic ...resonance imaging (MRI) using 18F-sodium fluoride (18F-NaF) to check simultaneously 18F-NaF uptake, a marker of microcalcifications, and morphological criteria of vulnerability.
We included 12 patients with either recently symptomatic or asymptomatic carotid stenosis. All patients underwent 18F-NaF PET/MRI. 18F-NaF target-to-background ratio (TBR) was measured in culprit and nonculprit (including contralateral plaques of symptomatic patients) plaques as well as in other arterial walls. Morphological criteria of vulnerability were assessed on MRI. Mineral metabolism markers were also collected. 18F-NaF uptake was higher in culprit compared to nonculprit plaques (median TBR 2.6 2.2-2.8 vs 1.7 1.3-2.2; P = 0.03) but was not associated with morphological criteria of vulnerability on MRI. We found a positive correlation between 18F-NaF uptake and calcium plaque volume and ratio but not with circulating tissue-nonspecific alkaline phosphatase (TNAP) activity and inorganic pyrophosphate (PPi) levels. 18F-NaF uptake in the other arterial walls did not differ between symptomatic and asymptomatic patients.
18F-NaF PET/MRI may be a promising tool for providing additional insights into the plaque vulnerability.
PDF
