Shortened Modified Look-Locker Inversion recovery (ShMOLLI) for clinical myocardial T1-mapping at 1.5 and 3 T within a 9 heartbeat breathhold

University of Oxford Centre for Clinical Magnetic Resonance Research, Department of Cardiovascular Medicine, John Radcliffe Hospital, Oxford, UK.
Journal of Cardiovascular Magnetic Resonance (Impact Factor: 4.56). 11/2010; 12(1):69. DOI: 10.1186/1532-429X-12-69
Source: PubMed


T1 mapping allows direct in-vivo quantitation of microscopic changes in the myocardium, providing new diagnostic insights into cardiac disease. Existing methods require long breath holds that are demanding for many cardiac patients. In this work we propose and validate a novel, clinically applicable, pulse sequence for myocardial T1-mapping that is compatible with typical limits for end-expiration breath-holding in patients.
The Shortened MOdified Look-Locker Inversion recovery (ShMOLLI) method uses sequential inversion recovery measurements within a single short breath-hold. Full recovery of the longitudinal magnetisation between sequential inversion pulses is not achieved, but conditional interpretation of samples for reconstruction of T1-maps is used to yield accurate measurements, and this algorithm is implemented directly on the scanner. We performed computer simulations for 100 ms<T1 < 2.7 s and heart rates 40-100 bpm followed by phantom validation at 1.5T and 3T. In-vivo myocardial T1-mapping using this method and the previous gold-standard (MOLLI) was performed in 10 healthy volunteers at 1.5T and 3T, 4 volunteers with contrast injection at 1.5T, and 4 patients with recent myocardial infarction (MI) at 3T.
We found good agreement between the average ShMOLLI and MOLLI estimates for T1 < 1200 ms. In contrast to the original method, ShMOLLI showed no dependence on heart rates for long T1 values, with estimates characterized by a constant 4% underestimation for T1 = 800-2700 ms. In-vivo, ShMOLLI measurements required 9.0 ± 1.1 s (MOLLI = 17.6 ± 2.9 s). Average healthy myocardial T1 s by ShMOLLI at 1.5T were 966 ± 48 ms (mean ± SD) and 1166 ± 60 ms at 3T. In MI patients, the T1 in unaffected myocardium (1216 ± 42 ms) was similar to controls at 3T. Ischemically injured myocardium showed increased T1 = 1432 ± 33 ms (p < 0.001). The difference between MI and remote myocardium was estimated 15% larger by ShMOLLI than MOLLI (p < 0.04) which suffers from heart rate dependencies for long T1. The in-vivo variability within ShMOLLI T1-maps was only 14% (1.5T) or 18% (3T) higher than the MOLLI maps, but the MOLLI acquisitions were twice longer than ShMOLLI acquisitions.
ShMOLLI is an efficient method that generates immediate, high-resolution myocardial T1-maps in a short breath-hold with high precision. This technique provides a valuable clinically applicable tool for myocardial tissue characterisation.

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Available from: Erica Dall'Armellina, Oct 09, 2015
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    • "A stack of short-axis imaging planes in the same orientation (from the base to the apex) was subsequently used for acquisition of native T1- maps as well as LGE as described below. Native T1-mapping was performed right after registration of SSFP cine images with means of the ShMOLLI sequence (Shortened Modified Look-Locker Inversion Recovery) acquisition scheme 5(1)1(1)1 with conditional post-processing; WIP448C, Syngo Version B17A [19]. "
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    ABSTRACT: Myocardial fibrosis was shown to influence prognosis in hypertrophic cardiomyopathy (HCM). It is typically assessed by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR). Native T1-mapping has been proposed, as a contrast-free method of fibrosis assessment. The aim of the study was to define a cut-off value for native T1 relaxation time that best reflects LGE quantification of myocardial fibrosis. In 25 patients with HCM and 20 controls we performed T1-mapping pre-contrast using ShMOLLI technique. This was followed by LGE assessment in the studied group 10 minutes after gadolinium contrast injection. Relative myocardial fibrosis size was calculated for varying T1 time thresholds (940-1100 ms) and compared with 6SD method for LGE. Median fibrosis size calculated with T1-mapping was insignificantly different from LGE only for native T1 time threshold of 1060 ms (p=0.62). Using this threshold, Bland-Altman plots demonstrated very good agreement between fibrosis sizes from the two methods (slightly better only for 1080 ms threshold). For threshold of 1060 ms we also observed good correlation (rho=0.73) with LGE 6SD method (insignificantly better for lower thresholds, best for threshold of 980 ms - rho=0.88). In control group with no diagnosis of HCM, fibrosis size <1% was reached for thresholds of 1040 ms and higher. Native T1-mapping can be used for non-contrast assessment of myocardial fibrosis in HCM. The 1060 ms threshold of the native T1 relaxation time is characterized by the best balance between agreement and correlation with fibrosis assessed by LGE 6 SD method. Copyright © 2015. Published by Elsevier Inc.
    Magnetic Resonance Imaging 04/2015; 33(6). DOI:10.1016/j.mri.2015.04.001 · 2.09 Impact Factor
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    • "Furthermore, quantitative mapping has the potential to provide fast and repeatable information, including automatic segmentation and classification of plaques according to the CMR-modified AHA scheme [5]. The concept of relaxation time mapping in cardiac studies has been a hot topic with regard to T1 mapping of the heart, where this method enables assessment of tissue viability without administering gadolinium-based contrast agents [7] or T2* mapping, where it provides validated quantitative information about iron overload in thalassemia patients [8]. Relaxation time mapping with regards to the heart is difficult due to its movement and time constraints, while the same idea applied to carotid artery plaques encounters the problem of high-resolution requirement due to the size of imaged structures. "
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    ABSTRACT: Atherosclerosis is regarded as a lifestyle disease, where artery lumen is reduced due to deposition of calcium and fatty materials such as cholesterol and triglyceride. These plaques can become unstable and rupture, resulting in life threatening cardiovascular events. Multicontrast cardiovascular magnetic resonance (CMR) has been used on 1.5T and 3T scanners to identify carotid plaques and study their morphology in vivo, however it does not provide quantitative information. Carotid arteries of healthy volunteers and patients with known atherosclerosis were imaged on a 1.5T Siemens Aera MRI scanner. Standard imaging protocol consisted of a TOF sequence to localize the carotid bifurcation, followed by the acquisition of T1-, T2- and PD-weighted images to assess the plaque qualitatively. Finally, T2 relaxation time mapping was performed through the plaque center using a Multiple-Spin-Echo sequence. Custom software was written in MATLAB to generate T2 maps and discriminate different plaque types, confirmed by multicontrast CMR. This study showed that T2 mapping of atherosclerotic plaque is possible on a 1.5T scanner. Measurements demonstrated the ability to discriminate plaque components on T2 maps, which are in good agreement with conventional multicontrast CMR.
    Computing in Cardiology Conference (CinC), 2014, Cambridge, MA; 09/2014
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    • "Native T1 maps (using ShMOLLI [12]), all with the same colour scale. (a) healthy volunteer: the myocardium appears homogenously green and the blood is red; low T1 values (blue) from iron overload (c) and lipid storage in Fabry’s disease (c) (except the infero-lateral wall which is high); (d) and (e) represent with high T1 values (red) in amyloid (d) and in myocarditis (d); infarcted (acute infarction) area appears red f) – here basal anter-septum "
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    ABSTRACT: Heart failure (HF) is a major and growing cause of morbidity and mortality. Despite initial successes, there have been few recent therapeutic advances. A better understanding of HF pathophysiology is needed with renewed focus on the myocardium itself. A new imaging technique is now available that holds promise. T1 mapping is a cardiovascular magnetic resonance (CMR) technique for non-invasive myocardial tissue characterization. T1 alters with disease. Pre-contrast (native) T1 changes with a number of processes such as fibrosis, edema and infiltrations. If a post contrast scan is also done, the extracellular volume fraction (ECV) can be measured, a direct measure of the interstitium and its reciprocal, the cell volume. This dichotomy is fundamental - and now measurable promising more targeted therapy and new insights into disease biology.
    Current Cardiovascular Imaging Reports 09/2014; 7(9):9287. DOI:10.1007/s12410-014-9287-8
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