Comparison of T1 mapping techniques for ECV quantification. Histological validation and reproducibility of ShMOLLI versus multibreath-hold T1 quantification equilibrium contrast CMR
ABSTRACT BACKGROUND: Myocardial extracellular volume (ECV) is elevated in fibrosis or infiltration and can be quantified by measuring the haematocrit with pre and post contrast T1 at sufficient contrast equilibrium. Equilibrium CMR (EQ-CMR), using a bolus-infusion protocol, has been shown to provide robust measurements of ECV using a multibreath-hold T1 pulse sequence. Newer, faster sequences for T1 mapping promise whole heart coverage and improved clinical utility, but have not been validated. METHODS: Multibreathhold T1 quantification with heart rate correction and single breath-hold T1 mapping using Shortened Modified Look-Locker Inversion recovery (ShMOLLI) were used in equilibrium contrast CMR to generate ECV values and compared in 3 ways.Firstly, both techniques were compared in a spectrum of disease with variable ECV expansion (n=100, 50 healthy volunteers, 12 patients with hypertrophic cardiomyopathy, 18 with severe aortic stenosis, 20 with amyloid). Secondly, both techniques were correlated to human histological collagen volume fraction (CVF%, n=18, severe aortic stenosis biopsies). Thirdly, an assessment of test:retest reproducibility of the 2 CMR techniques was performed 1 week apart in individuals with widely different ECVs (n=10 healthy volunteers, n=7 amyloid patients). RESULTS: More patients were able to perform ShMOLLI than the multibreath-hold technique (6% unable to breath-hold). ECV calculated by multibreath-hold T1 and ShMOLLI showed strong correlation (r2=0.892), little bias (bias -2.2%, 95%CI -8.9% to 4.6%) and good agreement (ICC 0.922, range 0.802 to 0.961, p<0.0001). ECV correlated with histological CVF% by multibreath-hold ECV (r2= 0.589) but better by ShMOLLI ECV (r2= 0.685). Inter-study reproducibility demonstrated that ShMOLLI ECV trended towards greater reproducibility than the multibreath-hold ECV, although this did not reach statistical significance (95%CI -4.9% to 5.4% versus 95%CI -6.4% to 7.3% respectively, p=0.21). CONCLUSIONS: ECV quantification by single breath-hold ShMOLLI T1 mapping can measure ECV by EQ-CMR across the spectrum of interstitial expansion. It is procedurally better tolerated, slightly more reproducible and better correlates with histology compared to the older multibreath-hold FLASH techniques.
Full-textDOI: · Available from: James C Moon, May 10, 2014
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ABSTRACT: Risk scores for cardiovascular disease (CVD) are in common use to integrate multiple cardiovascular risk factors in order to identify individuals at greatest risk for disease. The purpose of this study was to determine if individuals at greater cardiovascular risk have T1 mapping indices by cardiovascular magnetic resonance (CMR) indicative of greater myocardial fibrosis. CVD risk scores for 1208 subjects (men, 50.8%) ages 55-94 years old were evaluated in the Multiethnic Study of Atherosclerosis (MESA) at six centers. T1 times were determined at 1.5Tesla before and after gadolinium administration (0.15 mmol/kg) using a modified Look-Locker pulse sequence. The relationship between CMR measures (native T1, 12 and 25 minute post-gadolinium T1, partition coefficient and extracellular volume fraction) and 14 established different cardiovascular risk scores were determined using regression analysis. Bootstrapping analysis with analysis of variance was used to compare different CMR measures. CVD risk scores were significantly different for men and women (p < 0.001). 25 minute post gadolinium T1 time showed more statistically significant associations with risk scores (10/14 scores, 71%) compared to other CMR indices (e.g. native T1 (7/14 scores, 50%) and partition coefficient (7/14, 50%) in men. Risk scores, particularly the new 2013 AHA/ASCVD risk score, did not correlate with any CMR fibrosis index. Men with greater CVD risk had greater CMR indices of myocardial fibrosis. T1 times at greater delay time (25 minutes) showed better agreement with commonly used risk score indices compared to ECV and native T1 time. http://www.mesa-nhlbi.org/, NCT00005487.Journal of Cardiovascular Magnetic Resonance 12/2015; 17(1). DOI:10.1186/s12968-015-0121-5 · 5.11 Impact Factor
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ABSTRACT: Diffuse myocardial fibrosis may be quantified with cardiovascular magnetic resonance (CMR) by calculating extra-cellular volume (ECV) from native and post-contrast T1 values. Accurate ECV calculation is dependent upon the contrast agent having reached equilibrium within tissue compartments. Previous studies have used infusion or single bolus injections of contrast to calculate ECV. In clinical practice however, split dose contrast injection is commonly used as part of stress/rest perfusion studies. In this study we sought to assess the effects of split dose versus single bolus contrast administration on ECV calculation. Ten healthy volunteers and five patients ( 4 ischaemic heart disease, 1 hypertrophic cardiomyopathy) were studied on a 3.0 Tesla (Philips Achieva TX) MR system and underwent two (patients) or three (volunteers) separate CMR studies over a mean of 12 and 30 days respectively. Volunteers underwent one single bolus contrast study (Gadovist 0.15mmol/kg). In two further studies, contrast was given in two boluses (0.075mmol/kg per bolus) as part of a clinical adenosine stress/rest perfusion protocol, boluses were separated by 12 minutes. Patients underwent one bolus and one stress perfusion study only. T1 maps were acquired pre contrast and 15 minutes following the single bolus or second contrast injection. ECV agreed between bolus and split dose contrast administration (coefficient of variability 5.04%, bias 0.009, 95% CI -3.754 to 3.772, r2 = 0.973, p = 0.001)). Inter-study agreement with split dose administration was good (coefficient of variability, 5.67%, bias -0.018, 95% CI -4.045 to 4.009, r2 = 0.766, p > 0.001). ECV quantification using split dose contrast administration is reproducible and agrees well with previously validated methods in healthy volunteers, as well as abnormal and remote myocardium in patients. This suggests that clinical perfusion CMR studies may incorporate assessment of tissue composition by ECV based on T1 mapping.Journal of Cardiovascular Magnetic Resonance 12/2015; 17(1):6. DOI:10.1186/s12968-015-0112-6 · 5.11 Impact Factor
- Circulation Cardiovascular Imaging 11/2014; 7(6):860-2. DOI:10.1161/CIRCIMAGING.114.002700 · 6.75 Impact Factor