Quantification of common carotid artery and descending aorta vessel wall thickness from MR vessel wall imaging using a fully automated processing pipeline.

PURPOSE: To develop and evaluate a method that can fully automatically identify the vessel wall boundaries and quantify the wall thickness for both common carotid artery (CCA) and descending aorta (DAO) from axial magnetic resonance (MR) images. MATERIALS AND METHODS: 3T MRI data acquired with T1 -weighted gradient-echo black-blood imaging sequence from carotid (39 subjects) and aorta (39 subjects) were used to develop and test the algorithm. The vessel wall segmentation was achieved by respectively fitting a 3D cylindrical B-spline surface to the boundaries of lumen and outer wall. The tube-fitting was based on the edge detection performed on the signal intensity (SI) profile along the surface normal. To achieve a fully automated process, Hough Transform (HT) was developed to estimate the lumen centerline and radii for the target vessel. Using the outputs of HT, a tube model for lumen segmentation was initialized and deformed to fit the image data. Finally, lumen segmentation was dilated to initiate the adaptation procedure of outer wall tube. The algorithm was validated by determining: 1) its performance against manual tracing; 2) its interscan reproducibility in quantifying vessel wall thickness (VWT); 3) its capability of detecting VWT difference in hypertensive patients compared with healthy controls. Statistical analysis including Bland-Altman analysis, t-test, and sample size calculation were performed for the purpose of algorithm evaluation. RESULTS: The mean distance between the manual and automatically detected lumen/outer wall contours was 0.00 ± 0.23/0.09 ± 0.21 mm for CCA and 0.12 ± 0.24/0.14 ± 0.35 mm for DAO. No significant difference was observed between the interscan VWT assessment using automated segmentation for both CCA (P = 0.19) and DAO (P = 0.94). Both manual and automated segmentation detected significantly higher carotid (P = 0.016 and P = 0.005) and aortic (P < 0.001 and P = 0.021) wall thickness in the hypertensive patients. CONCLUSION: A reliable and reproducible pipeline for fully automatic vessel wall quantification was developed and validated on healthy volunteers as well as patients with increased vessel wall thickness. This method holds promise for helping in efficient image interpretation for large-scale cohort studies. LEVEL OF EVIDENCE: 4 J. Magn. Reson. Imaging 2017;45:215-228.

Aortic Arch Stiffness Is Associated With Incipient Brain Injury in Patients With Hypertension.

BACKGROUND: It has been shown that microstructural brain tissue damage can be detected in hypertension patients, while the underlying mechanisms are not fully understood. We aim to explore the association between diffusion tensor imaging (DTI) measures of brain injury and aortic arch pulse wave velocity (PWV) in hypertensive patients without clinically manifest cerebrovascular disease. METHODS: Sixty-six hypertension patients (30 men, mean age 46±14 years) were prospectively included. Aortic arch PWV was assessed using velocity-encoded magnetic resonance imaging (VE-MRI). Brain tissue integrity was assessed by using DTI. Multivariable linear regression analysis was performed to assess the association between aortic arch PWV and fractional anisotropy (FA), axial diffusivity (AxD), and radial diffusivity (RD). RESULTS: Increased aortic arch PWV was associated with decreased white matter FA (ß = -0.30, P = 0.018), increased gray matter AxD (ß = 0.28, P = 0.016), and increased gray and white matter RD (ß = 0.30, P = 0.008 and ß = 0.35, P = 0.003, respectively). These effects were independent of age, sex, body mass index, smoking, and white matter hyperintensity (WMH) volume. CONCLUSIONS: Aortic arch stiffness relates to incipient brain injury before overt brain abnormalities may become apparent in patients with hypertension.

Site-specific coupling between vascular wall thickness and function: an observational MRI study of vessel wall thickening and stiffening in hypertension.

OBJECTIVES: The objective of this study was to evaluate associations between aortic pulse wave velocity (PWV) and aortic and carotid vessel wall thickness (VWT) using cardiovascular magnetic resonance imaging (MRI) in patients with hypertension as compared with healthy adult volunteers. MATERIALS AND METHODS: Local medical ethics approval was obtained and the participants gave informed consent. Fifteen patients with hypertension (5 men and 10 women; mean [SD] age, 49 [14] years) and 15 age- and sex-matched healthy volunteers were prospectively included and compared. All participants underwent MRI examination for measuring aortic and carotid VWT and aortic PWV with well-validated MRI techniques at 1.5- and 3-T MRI systems: PWV was assessed from velocity-encoded MRI and VWT was assessed by using dual-inversion black-blood gradient-echo imaging techniques. Paired t tests were used for testing differences between the volunteers and the patients and Pearson correlation (r) and univariable and multivariable stepwise linear regression analyses were used to test associations between aortic and carotid arterial wall thickness and stiffness. RESULTS: Mean values for aortic PWV and aortic and carotid VWT (indexed for body surface area [BSA]) were all significantly higher in patients with hypertension as compared with the healthy volunteers (ie, aortic PWV, 7.0 ± 1.4 m/s vs 5.7 ± 1.3 m/s; aortic VWT/BSA, 0.12 ± 0.03 mL/m vs 0.10 ± 0.03 mL/m; carotid VWT/BSA, 0.04 ± 0.01 mL/m vs 0.03 ± 0.01 mL/m; all P < 0.01). Aortic PWV was highly correlated with aortic VWT/BSA (r = 0.76 and P = 0.002 in the patients vs r = 0.63 and P = 0.02 in the volunteers), and in the patients, aortic PWV was moderately correlated with carotid VWT/BSA (r = 0.50; P = 0.04). In the volunteers, correlation between aortic PWV and carotid VWT/BSA was not significant (r = 0.40; P = 0.13). In addition, aortic VWT/BSA was significantly correlated with carotid VWT/BSA, in both the patients (r = 0.60; P = 0.005) and volunteers (r = 0.57; P = 0.007). CONCLUSIONS: In the patients with hypertension and the healthy volunteers, the aortic PWV is associated more strongly with aortic wall thickness than with carotid wall thickness, reflecting site-specific coupling between vascular wall thickness and function.

Increased aortic stiffness measured by MRI in patients with type 1 diabetes mellitus and relationship to renal function.

OBJECTIVE: Arterial stiffness is an important predictor of cardiovascular disease in type 1 diabetes mellitus (DM). The purpose of this study was to investigate whether type 1 DM is associated with increased aortic stiffness as measured by MRI, independently of renal dysfunction, and to evaluate the relationship between aortic stiffness and renal function within the normal range in patients with type 1 DM. MATERIALS AND METHODS: We included 77 patients with type 1 DM (mean age, 46 ± 12 years) and 36 healthy control subjects matched for age and renal function in a cross-sectional study. Exclusion criteria consisted of microalbuminuria, renal impairment, aortic valve disease, and standard MRI contraindications. Aortic pulse wave velocity (PWV), a marker of aortic stiffness, was assessed by MRI. Renal function was expressed as the estimated glomerular filtration rate (GFR). Mann-Whitney U test and Spearman's correlation analysis were performed. Stepwise multivariable logarithmic regressions with forward entry analysis for estimated GFR were performed to study the relationship with aortic PWV using interaction terms for type 1 DM. RESULTS: Patients with type 1 DM without microalbuminuria or renal impairment show increased aortic PWV compared with control subjects (p < 0.05). There was a statistically significant correlation between estimated GFR and aortic PWV in patients with type 1 DM (p < 0.001; r = -0.427) and control subjects (p = 0.002; r = -0.502), with aortic PWV being increased in patients with type 1 DM for each given estimated GFR within the normal range (p < 0.001). The decrease in estimated GFR per increase in aortic PWV was similar for patients with type 1 DM and control subjects (p, not significant). CONCLUSION: Our data show that aortic stiffness, as measured by MRI, is increased and inversely related to renal function in patients with type 1 DM with normal albuminuria and normal estimated GFR.

Cerebral perfusion and aortic stiffness are independent predictors of white matter brain atrophy in type 1 diabetic patients assessed with magnetic resonance imaging.

OBJECTIVE: To identify vascular mechanisms of brain atrophy in type 1 diabetes mellitus (DM) patients by investigating the relationship between brain volumes and cerebral perfusion and aortic stiffness using magnetic resonance imaging (MRI). RESEARCH DESIGN AND METHODS: Approval from the local institutional review board was obtained, and patients gave informed consent. Fifty-one type 1 DM patients (30 men; mean age 44 ± 11 years; mean DM duration 23 ± 12 years) and 34 age- and sex-matched healthy control subjects were prospectively enrolled. Exclusion criteria comprised hypertension, stroke, aortic disease, and standard MRI contraindications. White matter (WM) and gray matter (GM) brain volumes, total cerebral blood flow (tCBF), total brain perfusion, and aortic pulse wave velocity (PWV) were assessed using MRI. Multivariable linear regression analysis was used for statistics, with covariates age, sex, mean arterial pressure, BMI, smoking, heart rate, DM duration, and HbA(1c). RESULTS: Both WM and GM brain volumes were decreased in type 1 DM patients compared with control subjects (WM P = 0.04; respective GM P = 0.03). Total brain perfusion was increased in type 1 DM compared with control subjects (ß = -0.219, P < 0.05). Total CBF and aortic PWV predicted WM brain volume (ß = 0.352, P = 0.024 for tCBF; respective ß = -0.458, P = 0.016 for aortic PWV) in type 1 DM. Age was the independent predictor of GM brain volume (ß = -0.695, P < 0.001). CONCLUSIONS: Type 1 DM patients without hypertension showed WM and GM volume loss compared with control subjects concomitant with a relative increased brain perfusion. Total CBF and stiffness of the aorta independently predicted WM brain atrophy in type 1 DM. Only age predicted GM brain atrophy.

Left ventricular diastolic function assessment from three-dimensional three-directional velocity-encoded MRI with retrospective valve tracking.

PURPOSE: To compare parameters describing left ventricular (LV) diastolic function obtained with three-dimensional (3D) three-directional velocity-encoded (VE) MRI with retrospective valve tracking and two-dimensional (2D) one-directional VE MRI in patients with ischemic heart failure. Second, to compare classification of LV diastolic function, and in particular for discriminating restrictive filling patterns, with both MRI techniques versus Doppler echocardiography. MATERIALS AND METHODS: The 3D and 2D VE MRI early (E) and atrial (A) peak flow rate indices, determined from transmitral waveform analyses, were compared. Also, net forward flow volume per cycle and transmitral regurgitation fraction were determined. Agreement in classifying diastolic filling patterns between 3D and 2D VE MRI versus Doppler echocardiography was evaluated using kappa statistics. RESULTS: The 3D three-directional VE MRI with retrospective valve tracking was statistically significantly different from 2D one-directional VE MRI for net forward flow volume and regurgitation fraction through the mitral valve and all parameters describing the diastolic waveform filling pattern, except for the E deceleration time and E/A filling ratio. Kappa-agreement between 3D three-directional VE MRI with retrospective valve tracking and echocardiography for classifying diastolic filling patterns was superior to 2D one-directional VE MRI and echocardiography (i.e., κ = 0.91 versus κ = 0.79, respectively). CONCLUSION: The 3D three-directional VE MRI with retrospective valve tracking better describes LV diastolic function as compared to 2D one-directional VE MRI in patients with ischemic heart failure.

Quantitative assessment of left ventricular function in humans at 7 T.

The purpose of this study was to determine the ability of 7 T cardiac magnetic resonance imaging (MRI) to quantitatively assess left ventricular volumes, mass, and function from cine short-axis series and left ventricular diastolic filling from velocity-encoded MRI in 10 healthy volunteers. As comparative "gold standard," the corresponding measures obtained at 1.5 T were taken. Left ventricular volumes, function, and mass were obtained by manual image segmentation. Trans-mitral flow graphs were obtained from 2D one-directional through-plane velocity-encoded MRI planned at the mitral valve in end-systole. Imaging at 7 T MRI was successful in 80% of the examinations. Assessment of left ventricular volumes, function, and mass at 7 T showed good agreement with 1.5 T (no significant differences between variables describing volumes, function, and mass with intraclass correlation coefficients ranging from 0.77 to 0.96). Trans-mitral stroke volume and the ratio between early and atrial peak filling rate showed strong agreement at both field strengths (no significant differences between stroke volumes and filling ratios with intraclass correlation coefficients 0.92 for stroke volumes and 0.77 for peak filling ratios). In conclusion, this study shows that assessing left ventricular volumes, function, and flow is feasible at 7 T MRI and that standardized MRI protocols provide similar quantitative results when compared with 1.5 T MRI.

Right coronary artery flow velocity and volume assessment with spiral K-space sampled breathhold velocity-encoded MRI at 3 tesla: accuracy and reproducibility.

PURPOSE: To evaluate accuracy and reproducibility of flow velocity and volume measurements in a phantom and in human coronary arteries using breathhold velocity-encoded (VE) MRI with spiral k-space sampling at 3 Tesla. MATERIALS AND METHODS: Flow velocity assessment was performed using VE MRI with spiral k-space sampling. Accuracy of VE MRI was tested in vitro at five constant flow rates. Reproducibility was investigated in 19 healthy subjects (mean age 25.4 +/- 1.2 years, 11 men) by repeated acquisition in the right coronary artery (RCA). RESULTS: MRI-measured flow rates correlated strongly with volumetric collection (Pearson correlation r = 0.99; P < 0.01). Due to limited sample resolution, VE MRI overestimated the flow rate by 47% on average when nonconstricted region-of-interest segmentation was used. Using constricted region-of-interest segmentation with lumen size equal to ground-truth luminal size, less than 13% error in flow rate was found. In vivo RCA flow velocity assessment was successful in 82% of the applied studies. High interscan, intra- and inter-observer agreement was found for almost all indices describing coronary flow velocity. Reproducibility for repeated acquisitions varied by less than 16% for peak velocity values and by less than 24% for flow volumes. CONCLUSION: 3T breathhold VE MRI with spiral k-space sampling enables accurate and reproducible assessment of RCA flow velocity.

Association of aortic arch pulse wave velocity with left ventricular mass and lacunar brain infarcts in hypertensive patients: assessment with MR imaging.

PURPOSE: To assess the possible association between aortic arch stiffness, which may cause hypertensive cardiovascular disease, and cardiac and cerebral end-organ damage in patients with hypertension by using magnetic resonance (MR) imaging. MATERIALS AND METHODS: Approval from the local institutional review board was obtained, and patients gave informed consent. Fifty patients with hypertension (31 women and 19 men; mean age +/- standard deviation, 49.2 years +/- 12.7; mean systolic blood pressure, 152.1 mm Hg +/- 22.3; mean diastolic blood pressure, 88.0 mm Hg +/- 13.1), compliant for treatment with antihypertensive medication, were prospectively enrolled for MR examinations of the aorta, heart, and brain with standard pulse sequences. Aortic arch pulse wave velocity (PWV), left ventricular (LV) mass, LV systolic and diastolic function, lacunar brain infarcts, and periventricular and deep white matter hyperintensities (WMHs) were assessed. Univariable and multiple linear and logistic regression analyses were used for statistical analyses. RESULTS: Mean aortic arch PWV was 7.3 m/sec +/- 2.5. Aortic arch PWV was statistically significantly associated with LV mass (r = 0.30, P = .03, beta = 1.73); indexes of systolic function, including ejection fraction (r = -0.38, P = .01, beta = -1.12); indexes of diastolic function, including the ratio of early diastolic to atrial contraction peak filling rates (r = -0.44, P < .01, beta = -0.11); lacunar brain infarcts (odds ratio [OR] = 1.8, P < .01); and periventricular (OR = 1.5, P = .01) and deep (OR = 1.6, P = .01) WMHs. Aortic arch PWV was statistically significantly associated with LV mass (r = 0.37, P = .03, beta = 2.11) and lacunar brain infarcts (OR = 1.8, P = .04), independent of age, sex, and hypertension duration, but not with indexes of diastolic and systolic function and WMHs. CONCLUSION: Aortic arch stiffness is associated with LV mass and lacunar brain infarcts in hypertensive patients, independent of age, sex, and hypertension duration; these manifestations of end-organ damage may help to risk stratify hypertensive patients.