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Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology.

ABSTRACT: AIMS:Conventional late gadolinium enhancement (LGE) cardiac magnetic resonance can detect myocardial infarction and some forms of non-ischaemic myocardial fibrosis. However, quantitative imaging of extracellular volume fraction (ECV) may be able to detect subtle abnormalities such as diffuse fibrosis or post-infarct remodelling of remote myocardium. The aims were (1) to measure ECV in myocardial infarction and non-ischaemic myocardial fibrosis, (2) to determine whether ECV varies with age, and (3) to detect sub-clinical abnormalities in 'normal appearing' myocardium remote from regions of infarction. METHODS AND RESULTS:Cardiac magnetic resonance ECV imaging was performed in 126 patients with T1 mapping before and after injection of gadolinium contrast. Conventional LGE images were acquired for the left ventricle. In patients with a prior myocardial infarction, the infarct region had an ECV of 51 ± 8% which did not overlap with the remote 'normal appearing' myocardium that had an ECV of 27 ± 3% (P < 0.001, n = 36). In patients with non-ischaemic cardiomyopathy, the ECV of atypical LGE was 37 ± 6%, whereas the 'normal appearing' myocardium had an ECV of 26 ± 3% (P < 0.001, n = 30). The ECV of 'normal appearing' myocardium increased with age (r = 0.28, P = 0.01, n = 60). The ECV of 'normal appearing' myocardium remote from myocardial infarctions increased as left ventricular ejection fraction decreased (r = -0.50, P = 0.02). CONCLUSION:Extracellular volume fraction imaging can quantitatively characterize myocardial infarction, atypical diffuse fibrosis, and subtle myocardial abnormalities not clinically apparent on LGE images. Taken within the context of prior literature, these subtle ECV abnormalities are consistent with diffuse fibrosis related to age and changes remote from infarction.

SUBMITTER: Ugander M

PROVIDER: S-EPMC3350985 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature

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Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology.

Ugander Martin M Oki Abiola J AJ Hsu Li-Yueh LY Kellman Peter P Greiser Andreas A Aletras Anthony H AH Sibley Christopher T CT Chen Marcus Y MY Bandettini W Patricia WP Arai Andrew E AE

European heart journal 20120124 10

<h4>Aims</h4>Conventional late gadolinium enhancement (LGE) cardiac magnetic resonance can detect myocardial infarction and some forms of non-ischaemic myocardial fibrosis. However, quantitative imaging of extracellular volume fraction (ECV) may be able to detect subtle abnormalities such as diffuse fibrosis or post-infarct remodelling of remote myocardium. The aims were (1) to measure ECV in myocardial infarction and non-ischaemic myocardial fibrosis, (2) to determine whether ECV varies with ag ...[more]

PMID: 22279111

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Project description:Fractional myocardial blood volume (fMBV) estimated using ferumoxytol-enhanced magnetic resonance imaging (MRI) (FE-MRI) has the potential to capture a hemodynamic response to myocardial hypoperfusion during contrast steady state without reliance on gadolinium chelates. Ferumoxytol has a long intravascular half-life and its use for steady-state MRI is off-label. The aim of this prospective study was to optimize and evaluate a two-compartment model for estimation of fMBV based on FE-MRI. Nine healthy swine and one swine with artificially induced single-vessel coronary stenosis underwent MRI on a 3.0 T clinical magnet. Myocardial longitudinal spin-lattice relaxation rate (R1) was measured using the 5(3)3(3)3 modified Look-Locker inversion recovery (MOLLI) sequence before and at contrast steady state following seven ferumoxytol infusions (0.125-4.0 mg/kg). fMBV and water exchange were estimated using a two-compartment model. Model-fitted fMBV was compared to simple fast-exchange fMBV approximation and percent change in pre- and postferumoxytol R1. Dose undersampling schemes were investigated to reduce acquisition duration. Variation in fMBV was assessed using one-way analysis of variance. Fast-exchange fMBV and ferumoxytol dose undersampling were evaluated using Bland-Altman analysis. Healthy normal swine showed a mean mid-ventricular fMBV of 7.2 ± 1.4% and water exchange rate of 11.3 ± 5.1 s-1 . There was intersubject variation in fMBV (p < 0.05) without segmental variation (p = 0.387). fMBV derived from eight-dose and four-dose sampling schemes had no significant bias (mean difference = 0.07, p = 0.541, limits of agreement -1.04% [-1.45, -0.62%] to 1.18% [0.77, 1.59%]). Pixel-wise fMBV in one swine model with coronary artery stenosis showed elevated fMBV in ischemic segments (apical anterior: 11.90 ± 4.00%, apical septum: 16.10 ± 5.71%) relative to remote segments (apical inferior: 9.59 ± 3.35%, apical lateral: 9.38 ± 2.35%). A two-compartment model based on FE-MRI using the MOLLI sequence may enable estimation of fMBV in studies of ischemic heart disease. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2.

Project description:ObjectivesTo investigate the effect of the phantom-based correction method for standardizing myocardial native T1 and extracellular volume fraction (ECV) in healthy subjects.MethodsSeventy-one healthy asymptomatic adult (≥ 20 years) volunteers of five different age groups (34 men and 37 women, 45.5 ± 15.5 years) were prospectively enrolled in three academic hospitals. Cardiac MRI including Modified Look - Locker Inversion recovery T1 mapping sequence was performed using a 3-Tesla system with a different type of scanner for each hospital. Native T1 and ECV were measured in the short-axis T1 map and analyzed for mean values of the 16 entire segments. The myocardial T1 value of each subject was corrected based on the site-specific equation derived from the T1 Mapping and ECV Standardization phantom. The global native T1 and ECV were compared between institutions before and after phantom-based correction, and the variation in native T1 and ECV among institutions was assessed using a coefficient of variation (CoV).ResultsThe global native T1 value significantly differed between the institutions (1198.7 ± 32.1 ms, institution A; 1217.7 ± 39.9 ms, institution B; 1232.7 ± 31.1 ms, institution C; p = 0.002), but the mean ECV did not (26.6-27.5%, p = 0.355). After phantom-based correction, the global native T1 and ECV were 1289.7 ± 32.4 ms and 25.0 ± 2.7%, respectively, and CoV for native T1 between the three institutions decreased from 3.0 to 2.5%. The corrected native T1 value did not significantly differ between institutions (1284.5 ± 31.5 ms, institution A; 1296.5 ± 39.1 ms, institution B; 1291.3 ± 29.3 ms, institution C; p = 0.440), and neither did the ECV (24.4-25.9%, p = 0.078).ConclusionsThe phantom-based correction method can provide standardized reference T1 values in healthy subjects.Key points• After phantom-based correction, the global native T1 of 16 entire myocardial segments on 3-T cardiac MRI is 1289.4 ± 32.4 ms, and the extracellular volume fraction was 25.0 ± 2.7% for healthy subjects. • After phantom - based correction was applied, the differences in the global native T1 among institutions became insignificant, and the CoV also decreased from 3.0 to 2.5%.

Project description:BACKGROUND:End-stage renal disease (ESRD) patients are at high cardiovascular risk, and myocardial fibrosis (MF) accounts for most of their cardiac events. The purpose of this study is to investigate the prognostic value and risk stratification of MF as measured by extracellular volume (ECV) on cardiac magnetic resonance (CMR) for heart failure (HF) in patients with hemodialysis-dependent ESRD. METHODS:Sixty-six hemodialysis ESRD patients and 25 matched healthy volunteers were prospectively enrolled and underwent CMR to quantify multiple parameters of MF by T1 mapping and late gadolinium enhancement (LGE). All ESRD patients were followed up for 11-30?months, and the end-point met the 2016 ESC guidelines for the definition of HF. RESULTS:Over a median follow-up of 18?months (range 11-30?months), there were 26 (39.39%) guideline-diagnosed HF patients in the entire cohort of ESRD subjects. The native T1 value was elongated, and ECV was enlarged in the HF cohort relative to the non-HF cohort and normal controls (native T1, 1360.10?±?50.14?ms, 1319.39?±?55.44?ms and 1276.35?±?56.56?ms; ECV, 35.42?±?4.42%, 31.85?±?3.01% and 26.97?±?1.87%; all p<0.05). In the cardiac strain analysis, ECV was significantly correlated with global radial strain (GRS) (r?=?-?0.501, p?=?0.009), global circumferential strain (GCS) (r?=?0.553, p?=?0.005) and global longitudinal strain (GLS) (r?=?0.507, p?=?0.008) in ESRD patients with HF. Cox proportional hazard regression models revealed that ECV (hazard ratio [HR]?=?1.160, 95% confidence interval: 1.022 to 1.318, p?=?0.022) was the only independent predictor of HF in ESRD patients. It also had a higher diagnostic accuracy for detecting MF (area under the curve [AUC]?=?0.936; 95% confidence interval: 0.864 to 0.976) than native T1 and post T1 (all p???0.002). Kaplan-Meier analysis revealed that the high-ECV group had a shorter median overall survival time than the low-ECV group (18?months vs. 20?months, log-rank p?=?0.046) and that ESRD patients with high ECV were more likely to have HF. CONCLUSIONS:Myocardial fibrosis quantification by ECV on CMR T1 mapping was shown to be an independent risk factor of heart failure, providing incremental prognostic value and risk stratification for cardiac events in ESRD patients. TRIAL REGISTRATION:Chinese Clinical Trial Registry ChiCTR-DND-17012976, 13/12/2017, Retrospectively registered.

Project description:BackgroundVentricular arrhythmia in hypertrophic cardiomyopathy (HCM) relates to adverse structural change and genetic status. Cardiovascular magnetic resonance (CMR)-guided electrocardiographic imaging (ECGI) noninvasively maps cardiac structural and electrophysiological (EP) properties.ObjectivesThe purpose of this study was to establish whether in subclinical HCM (genotype [G]+ left ventricular hypertrophy [LVH]-), ECGI detects early EP abnormality, and in overt HCM, whether the EP substrate relates to genetic status (G+/G-LVH+) and structural phenotype.MethodsThis was a prospective 211-participant CMR-ECGI multicenter study of 70 G+LVH-, 104 LVH+ (51 G+/53 G-), and 37 healthy volunteers (HVs). Local activation time (AT), corrected repolarization time, corrected activation-recovery interval, spatial gradients (GAT/GRTc), and signal fractionation were derived from 1,000 epicardial sites per participant. Maximal wall thickness and scar burden were derived from CMR. A support vector machine was built to discriminate G+LVH- from HV and low-risk HCM from those with intermediate/high-risk score or nonsustained ventricular tachycardia.ResultsCompared with HV, subclinical HCM showed mean AT prolongation (P = 0.008) even with normal 12-lead electrocardiograms (ECGs) (P = 0.009), and repolarization was more spatially heterogenous (GRTc: P = 0.005) (23% had normal ECGs). Corrected activation-recovery interval was prolonged in overt vs subclinical HCM (P < 0.001). Mean AT was associated with maximal wall thickness; spatial conduction heterogeneity (GAT) and fractionation were associated with scar (all P < 0.05), and G+LVH+ had more fractionation than G-LVH+ (P = 0.002). The support vector machine discriminated subclinical HCM from HV (10-fold cross-validation accuracy 80% [95% CI: 73%-85%]) and identified patients at higher risk of sudden cardiac death (accuracy 82% [95% CI: 78%-86%]).ConclusionsIn the absence of LVH or 12-lead ECG abnormalities, HCM sarcomere gene mutation carriers express an aberrant EP phenotype detected by ECGI. In overt HCM, abnormalities occur more severely with adverse structural change and positive genetic status.

Project description:Background: Non-invasive characterization of the pathological features of Alzheimer's disease (AD) could enhance patient management and the development of therapeutic strategies. Magnetic resonance imaging texture analysis (MRTA) has been used previously to extract texture descriptors from structural clinical scans in AD to determine cerebral tissue heterogeneity. In this study, we examined the potential of MRTA to specifically identify tau pathology in an AD mouse model and compared the MRTA metrics to histological measures of tau burden. Methods: MRTA was applied to T2 weighted high-resolution MR images of nine 8.5-month-old rTg4510 tau pathology (TG) mice and 16 litter matched wild-type (WT) mice. MRTA comprised of the filtration-histogram technique, where the filtration step extracted and enhanced features of different sizes (fine, medium, and coarse texture scales), followed by quantification of texture using histogram analysis (mean gray level intensity, mean intensity, entropy, uniformity, skewness, standard-deviation, and kurtosis). MRTA was applied to manually segmented regions of interest (ROI) drawn within the cortex, hippocampus, and thalamus regions and the level of tau burden was assessed in equivalent regions using histology. Results: Texture parameters were markedly different between WT and TG in the cortex (E, p < 0.01, K, p < 0.01), the hippocampus (K, p < 0.05) and in the thalamus (K, p < 0.01). In addition, we observed significant correlations between histological measurements of tau burden and kurtosis in the cortex, hippocampus and thalamus. Conclusions: MRTA successfully differentiated WT and TG in brain regions with varying degrees of tau pathology (cortex, hippocampus, and thalamus) based on T2 weighted MR images. Furthermore, the kurtosis measurement correlated with histological measures of tau burden. This initial study indicates that MRTA may have a role in the early diagnosis of AD and the assessment of tau pathology using routinely acquired structural MR images.

Project description:BACKGROUND:Characterization of tissue integrity and inflammatory processes after acute myocardial infarction (AMI) using non-invasive imaging is predictive of patient outcome. Quantitative cardiovascular magnetic resonance (CMR) techniques such as native T1 and extracellular volume (ECV) mapping as well as 18F-FDG positron emission tomography (PET) imaging targeting inflammatory cell populations are gaining acceptance, but are often applied without assessing their quantitative potential. Using simultaneously acquired PET/CMR data from patients early after AMI, this study quantitatively compares these three imaging markers and investigates links to blood markers of myocardial injury and systemic inflammatory activity. METHODS:A total of 25 patients without microvascular obstruction were retrospectively recruited. All imaging was simultaneously performed 5 ± 1 days after revascularization following AMI on an integrated 3T PET/MRI scanner. Native and post-contrast T1 data were acquired using a modified Look-Locker inversion recovery (MOLLI) sequence, ECV maps were calculated using individually sampled hematocrit. 18F-FDG PET was executed after 1 day of dietary preparation, 12 h of fasting, and administration of heparin. ECV, 18F-FDG and native T1 data were compared mutually as well as to peak counts of peripheral blood markers (creatine kinase, creatine kinase-MB, troponin, leukocytes, monocytes) and infarct size. RESULTS:High intra-patient correlations of relative ECV, 18F-FDG PET and native T1 signal increases were observed in combination with no inter-patient correlation of maximum absolute values at the infarct center, suggesting well-colocalized but physiologically diverse processes begetting the respective image signals. Comparison of maximum image signals to markers of myocardial damage and systemic inflammation yielded highly significant correlations of ECV to peak creatine kinase-MB and overall infarct size as well as between native T1 and peak monocyte counts. CONCLUSIONS:Absolute native T1 values at the infarct core early after AMI can be linked to the systemic inflammatory response independent of infarct size. Absolute ECV at the infarct core is related to both infarct size and blood markers of myocardial damage.

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Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology.

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Extracellular volume imaging by magnetic resonance imaging provides insights into overt and sub-clinical myocardial pathology.

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