Comparison of In Vivo Carotid 3.0-T Magnetic Resonance to B-Mode Ultrasound Imaging and Histology in a Porcine Model

Brain atrophy, reduced cerebral perfusion, arterial stiffening, and wall thickening with aging coincide with stimulus-specific changes in fMRI-BOLD responses

The aim of this study was to investigate how aging affects blood flow and structure of the brain. It was hypothesized older individuals would have lower gray matter volume (GMV), resting cerebral blood flow (CBF0), and depressed responses to isometabolic and neurometabolic stimuli. In addition, increased carotid-femoral pulse-wave velocity (PWV), carotid intima-media thickness (IMT), and decreased brachial flow-mediated dilation (FMD) would be associated with lower CBF0, cerebrovascular reactivity (CVR), and GMV. Brain scans (magnetic resonance imaging) and cardiovascular examinations were conducted in young (age = 24 ± 3 yr, range = 22-28 yr; n = 13) and old (age = 71 ± 4 yr; range = 67-82 yr, n = 14) participants, and CBF0, CVR [isometabolic % blood oxygen level-dependent (BOLD) in response to a breath hold (BH)], brain activation patterns during a working memory task (neurometabolic %BOLD response to N-back trial), GMV, PWV, IMT, and FMD were measured. CBF0 and to a lesser extent CVRBH were lower in the old group (P ≤ 0.050); however, the increase in the %BOLD response to the memory task was not blunted (P ≥ 0.2867). Age-related differential activation patterns during the working memory task were characterized by disinhibition of the default mode network in the old group (P < 0.0001). Linear regression analyses revealed PWV, and IMT were negatively correlated with CBF0, CVRBH, and GMV across age groups, but within the old group alone only the relationships between PWV-CVRBH and IMT-GMV remained significant (P ≤ 0.0183). These findings suggest the impacts of age on cerebral %BOLD responses are stimulus specific, brain aging involves alterations in cerebrovascular and possibly neurocognitive control, and arterial stiffening and wall thickening may serve a role in cerebrovascular aging.NEW & NOTEWORTHY Cerebral perfusion was lower in old versus young adults. %Blood oxygen level-dependent (BOLD) responses to an isometabolic stimulus and gray matter volume were decreased in old versus young adults and associated with arterial stiffening and wall thickening. The increased %BOLD response to a neurometabolic stimulus appeared unaffected by age; however, the old group displayed disinhibition of the default mode network during the stimulus. Thus, age-related alterations in cerebral %BOLD responses were stimulus specific and related to arterial remodeling.

Quantitative assessment of carotid artery atherosclerosis by three-dimensional magnetic resonance and two-dimensional ultrasound imaging: a comparison study

Background

It has been proven that magnetic resonance (MR) and ultrasound imaging are useful tools in the quantification of carotid atherosclerotic plaques. However, there are only a few pieces of evidence to illustrate the links of quantitative measurements of carotid plaques between MR and ultrasound imaging. This study looked to compare the quantitative measurements of carotid plaques and investigate their relationship between three-dimensional (3D) MR vessel wall imaging and two-dimensional (2D) ultrasound imaging.

Methods

Seventy-five asymptomatic elderly subjects (mean age: 73.3±5.7 years; 45 males) with carotid atherosclerotic plaques diagnosed by both ultrasound and MR imaging were included in this study. The plaque size, including the maximum wall thickness (Max WT), plaque length, and plaque area, was measured by 3D MR and ultrasound imaging on longitudinal and cross-sectional views. The quantitative assessments of carotid plaque size were compared and correlated between 3D MR and 2D ultrasound imaging.

Results

In total, the quantitative measurements of 101 plaques on longitudinal views or 44 plaques on cross-sectional views of both MR and ultrasound imaging were compared. The Max WT of the plaques (longitudinal: 2.9±0.8 vs. 2.4±0.9 mm; cross-sectional: 3.2±1.1 vs. 2.6±0.7 mm) and plaque areas (longitudinal: 24.3±13.4 vs. 17.0±12.7 mm²; cross-sectional: 24.9±24.6 vs. 16.8±13.3 mm²) measured by MR imaging were found to be significantly higher than those measured by ultrasound imaging (all P<0.001). Moderate to strong correlations were found in Max WT, plaque area, plaque length between 3D MR and ultrasound imaging.

Conclusions

The quantitative measurements of carotid plaques using 3D MR and 2D ultrasound are significantly correlated. The plaque area and Max WT measured by 3D MR imaging are more significant than these parameters measured by 2D ultrasound imaging, which might be explained by the resolution of MR imaging and the workflow of measurements.

Vessel wall characterization using quantitative MRI: what's in a number?

The past decade has witnessed the rapid development of new MRI technology for vessel wall imaging. Today, with advances in MRI hardware and pulse sequences, quantitative MRI of the vessel wall represents a real alternative to conventional qualitative imaging, which is hindered by significant intra- and inter-observer variability. Quantitative MRI can measure several important morphological and functional characteristics of the vessel wall. This review provides a detailed introduction to novel quantitative MRI methods for measuring vessel wall dimensions, plaque composition and permeability, endothelial shear stress and wall stiffness. Together, these methods show the versatility of non-invasive quantitative MRI for probing vascular disease at several stages. These quantitative MRI biomarkers can play an important role in the context of both treatment response monitoring and risk prediction. Given the rapid developments in scan acceleration techniques and novel image reconstruction, we foresee the possibility of integrating the acquisition of multiple quantitative vessel wall parameters within a single scan session.

Novel anti-inflammatory strategies in atherosclerosis

PURPOSE OF REVIEW

Inflammation has been widely acknowledged to contribute throughout all stages of atherogenesis. However, these recent advances in our understanding have not been translated into clinical practice in which the mainstay of treatment is still lipid-targeted therapy. This review provides an overview of promising anti-inflammatory therapies in atherosclerosis, and discusses potential drawbacks and clinical benefits.

RECENT FINDINGS

Immunosuppressive drugs are likely to beneficially affect atherogenesis. Several novel anti-inflammatory targets have been scrutinized, of which some have reached clinical development stage, such as cytokine targets interleukin-1 and interleukin-6, CCR2 antagonist, selective phospholipase, and leukotriene inhibitors. Novel imaging modalities such as MRI and PET-computed tomography provide valuable surrogate inflammatory endpoints for risk stratification and testing anti-inflammatory agents in cardiovascular randomized trials.

SUMMARY

Anti-inflammatory therapies hold great promise in cardiovascular prevention regimens; however, atherosclerosis is a chronic disease, and systemic long-term use of anti-inflammatory agents carries the risk of complications arising from immunosuppression. In order to successfully add immunosuppressive drugs to our routine armament, we need to identify high-risk patients who benefit from anti-inflammatory treatment, increase our insight into the inflammatory pathogenesis of atherogenesis, and find safe and effective compounds capable of directly suppressing plaque inflammation.

ABCA1 mutation carriers with low high-density lipoprotein cholesterol are characterized by a larger atherosclerotic burden

AIMS

Low HDL-C is a potent risk factor for cardiovascular disease (CVD). Yet, mutations in ABCA1, a major determinant of circulating HDL-C levels, were previously not associated with CVD risk in cohort studies. To study the consequences of low plasma levels of high-density lipoprotein cholesterol (HDL-C) due to ATP-binding cassette transporter A1 (ABCA1) dysfunction for atherosclerotic vascular disease in the carotid arteries.

METHODS AND RESULTS

We performed 3.0 Tesla magnetic resonance imaging (MRI) measurements of the carotid arteries in 36 carriers of high impact functional ABCA1 mutations and 36 normolipidemic controls. Carriers presented with 42% lower HDL-C levels (P < 0.001), a larger mean wall area (18.6 ± 6.0 vs. 15.8 ± 4.3 mm(2); P = 0.02), a larger mean wall thickness (0.82 ± 0.21 vs. 0.70 ± 0.14 mm; P = 0.005), and a higher normalized wall index (0.37 ± 0.06 vs. 0.33 ± 0.04; P = 0.005) compared with controls, retaining significance after adjustment for smoking, alcohol consumption, systolic blood pressure, diabetes, body mass index, history of CVD, LDL-C, and statin use (P = 0.002).

CONCLUSION

Carriers of loss of function ABCA1 mutations display a larger atherosclerotic burden compared with age and sex-matched controls, implying a higher risk for CVD. Further studies are needed to elucidate the full function of ABCA1 in the protection against atherosclerosis. These data support the development of strategies to up-regulate ABCA1 in patients with established CVD.

Carriers of lecithin cholesterol acyltransferase gene mutations have accelerated atherogenesis as assessed by carotid 3.0-T magnetic resonance imaging [corrected]

OBJECTIVES

The aim of this study was to investigate the role of reduced lecithin: cholesterol acyltransferase (LCAT) function on atherogenesis using 3.0-T carotid magnetic resonance imaging (MRI) and B-mode ultrasound.

BACKGROUND

The role of low high-density lipoprotein cholesterol as a causal factor in atherogenesis has recently been questioned. LCAT plays a key role in high-density lipoprotein cholesterol metabolism.

METHODS

Carotid 3.0-T MRI and B-mode ultrasound measurements were performed in 40 carriers of LCAT gene mutations and 40 controls, matched for age. Patients with cardiovascular disease were excluded.

RESULTS

Carriers had 31% lower LCAT activity levels and 38% decreased high-density lipoprotein cholesterol levels (both p < 0.001 vs. controls). Carriers presented with a 10% higher normalized wall index (0.34 ± 0.07 vs. 0.31 ± 0.04, p = 0.002), a 22% higher mean wall area (17.3 ± 8.5 mm(2) vs. 14.2 ± 4.1 mm(2), p = 0.01), and a 22% higher total wall volume (1,039 ± 508 mm(3) vs. 851 ± 247 mm(3), p = 0.01 vs. controls) as measured by MRI. The prevalence (20 vs. 5, p = 0.002) and the total volume (102 mm(3) vs. 3 mm(3)) of atherosclerotic plaque components on MRI relating to lipid-rich tissue or calcification were also higher in carriers than in controls. All differences retained significance after adjustment for age, sex, blood pressure, low-density lipoprotein cholesterol, body mass index, smoking, and family history of cardiovascular disease. Common carotid intima-media thickness measured with ultrasound was increased in carriers by 12.5% (0.72 ± 0.33 mm vs. 0.64 ± 0.15 mm, p = 0.14).

CONCLUSIONS

Carriers of LCAT gene mutations exhibit increased carotid atherosclerosis, indicating an increased risk of cardiovascular disease. The present findings imply that increasing LCAT activity may be an attractive target in cardiovascular prevention strategies.

High resolution carotid black-blood 3T MR with parallel imaging and dedicated 4-channel surface coils

BACKGROUND

Most of the carotid plaque MR studies have been performed using black-blood protocols at 1.5 T without parallel imaging techniques. The purpose of this study was to evaluate a multi-sequence, black-blood MR protocol using parallel imaging and a dedicated 4-channel surface coil for vessel wall imaging of the carotid arteries at 3 T.

MATERIALS AND METHODS

14 healthy volunteers and 14 patients with intimal thickening as proven by duplex ultrasound had their carotid arteries imaged at 3 T using a multi-sequence protocol (time-of-flight MR angiography, pre-contrast T1w-, PDw- and T2w sequences in the volunteers, additional post-contrast T1w- and dynamic contrast enhanced sequences in patients). To assess intrascan reproducibility, 10 volunteers were scanned twice within 2 weeks.

RESULTS

Intrascan reproducibility for quantitative measurements of lumen, wall and outer wall areas was excellent with intraclass correlation coefficients >0.98 and measurement errors of 1.5%, 4.5% and 1.9%, respectively. Patients had larger wall areas than volunteers in both common carotid and internal carotid arteries and smaller lumen areas in internal carotid arteries (p < 0.001). Positive correlations were found between wall area and cardiovascular risk factors such as age, hypertension, coronary heart disease and hypercholesterolemia (Spearman's r = 0.45-0.76, p < 0.05). No significant correlations were found between wall area and body mass index, gender, diabetes or a family history of cardiovascular disease.

CONCLUSION

The findings of this study indicate that high resolution carotid black-blood 3 T MR with parallel imaging is a fast, reproducible and robust method to assess carotid atherosclerotic plaque in vivo and this method is ready to be used in clinical practice.