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3D myocardial T 1 mapping using saturation recovery

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      Abstract

      Purpose

      To propose a 3D quantitative high‐resolution T 1 mapping technique, called 3D SASHA (saturation‐recovery single‐shot acquisition), which combines a saturation recovery pulse with 1D‐navigator‐based‐respiratory motion compensation to acquire the whole volume of the heart in free breathing. The sequence was tested and validated both in a T 1 phantom and in healthy subjects.

      Materials and Methods

      The 3D SASHA method was implemented on a 1.5T scanner. A diaphragmatic navigator was used to allow free‐breathing acquisition and the images were acquired with a resolution of 1.4 × 1.4 × 8 mm 3. For assessment of accuracy and precision the sequence was compared with the reference gold‐standard inversion‐recovery spin echo (IRSE) pulse sequence in a T 1 phantom, while for the in vivo studies (10 healthy volunteers) 3D SASHA was compared with the clinically used 2D MOLLI (3‐3‐5) and 2D SASHA protocols.

      Results

      There was good agreement between the T 1 values measured in a T 1 phantom with 3D SASHA and the reference IRSE pulse sequences (1111.6 ± 31 msec vs. 1123.6 ± 8 msec, P = 0.9947). Mean and standard deviation of the myocardial T 1 values in healthy subjects measured with 2D MOLLI, 2D SASHA, and 3D SASHA sequences were 881 ± 40 msec, 1181.3 ± 32 msec, and 1153.6 ± 28 msec respectively.

      Conclusion

      The proposed 3D SASHA sequence allows for high‐resolution free‐breathing whole‐heart T 1‐mapping with T 1 values in good agreement with the 2D SASHA and improved precision.

      Level of Evidence: 2

      Technical Efficacy: Stage 1

      J. MAGN. RESON. IMAGING 2017;46:218–227

      Related collections

      Most cited references 27

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      Interrater reliability: the kappa statistic

       Mary L McHugh (2012)
      The kappa statistic is frequently used to test interrater reliability. The importance of rater reliability lies in the fact that it represents the extent to which the data collected in the study are correct representations of the variables measured. Measurement of the extent to which data collectors (raters) assign the same score to the same variable is called interrater reliability. While there have been a variety of methods to measure interrater reliability, traditionally it was measured as percent agreement, calculated as the number of agreement scores divided by the total number of scores. In 1960, Jacob Cohen critiqued use of percent agreement due to its inability to account for chance agreement. He introduced the Cohen’s kappa, developed to account for the possibility that raters actually guess on at least some variables due to uncertainty. Like most correlation statistics, the kappa can range from −1 to +1. While the kappa is one of the most commonly used statistics to test interrater reliability, it has limitations. Judgments about what level of kappa should be acceptable for health research are questioned. Cohen’s suggested interpretation may be too lenient for health related studies because it implies that a score as low as 0.41 might be acceptable. Kappa and percent agreement are compared, and levels for both kappa and percent agreement that should be demanded in healthcare studies are suggested.
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        Modified Look-Locker inversion recovery (MOLLI) for high-resolution T1 mapping of the heart.

        A novel pulse sequence scheme is presented that allows the measurement and mapping of myocardial T1 in vivo on a 1.5 Tesla MR system within a single breath-hold. Two major modifications of conventional Look-Locker (LL) imaging are introduced: 1) selective data acquisition, and 2) merging of data from multiple LL experiments into one data set. Each modified LL inversion recovery (MOLLI) study consisted of three successive LL inversion recovery (IR) experiments with different inversion times. We acquired images in late diastole using a single-shot steady-state free-precession (SSFP) technique, combined with sensitivity encoding to achieve a data acquisition window of < 200 ms duration. We calculated T1 using signal intensities from regions of interest and pixel by pixel. T1 accuracy at different heart rates derived from simulated ECG signals was tested in phantoms. T1 estimates showed small systematic error for T1 values from 191 to 1196 ms. In vivo T1 mapping was performed in two healthy volunteers and in one patient with acute myocardial infarction before and after administration of Gd-DTPA. T1 values for myocardium and noncardiac structures were in good agreement with values available from the literature. The region of infarction was clearly visualized. MOLLI provides high-resolution T1 maps of human myocardium in native and post-contrast situations within a single breath-hold. Copyright 2004 Wiley-Liss, Inc.
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          Equilibrium contrast cardiovascular magnetic resonance for the measurement of diffuse myocardial fibrosis: preliminary validation in humans.

          Diffuse myocardial fibrosis is a final end point in most cardiac diseases. It is missed by the cardiovascular magnetic resonance (CMR) late gadolinium enhancement technique. Currently, quantifying diffuse myocardial fibrosis requires invasive biopsy, with inherent risk and sampling error. We have developed a robust and noninvasive technique, equilibrium contrast CMR (EQ-CMR) to quantify diffuse fibrosis and have validated it against the current gold standard of surgical myocardial biopsy. The 3 principles of EQ-CMR are a bolus of extracellular gadolinium contrast followed by continuous infusion to achieve equilibrium; a blood sample to measure blood volume of distribution (1-hematocrit); and CMR to measure pre- and postequilibrium T1 (with heart rate correction). The myocardial volume of distribution is calculated, reflecting diffuse myocardial fibrosis. Clinical validation occurred in patients undergoing aortic valve replacement for aortic stenosis or myectomy in hypertrophic cardiomyopathy (n=18 and n=8, respectively). Surgical biopsies were analyzed for picrosirius red fibrosis quantification on histology. The mean histological fibrosis was 20.5+/-11% in aortic stenosis and 17.1+/-7.4% in hypertrophic cardiomyopathy. EQ-CMR correlated strongly with biopsy histological fibrosis: aortic stenosis, r(2)=0.86, Kendall Tau coefficient (T)=0.71, P<0.001; hypertrophic cardiomyopathy, r(2)=0.62, T=0.52, P=0.08; combined r(2)=0.80, T=0.67, P<0.001. We have developed and validated a new technique, EQ-CMR, to measure diffuse myocardial fibrosis as an add-on to a standard CMR scan, which allows for the noninvasive quantification of the diffuse fibrosis burden in myocardial diseases.
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            Author and article information

            Affiliations
            [ 1 ] Division of Imaging Science and Biomedical Engineering King's College London London UK
            [ 2 ] Philips Health Systems London UK
            [ 3 ] Wellcome Trust and EPSRC Medical Engineering Center, King's College London UK
            [ 4 ] BHF Centre of Excellence, King's College London UK
            [ 5 ] NIHR Biomedical Research Centre, King's College London
            [ 6 ] Pontificia Universidad Católica de Chile, Escuela de Ingeniería Santiago, Chile
            Author notes
            [* ]Address reprint requests to: G.N., Biomedical Engineering Department, King's College London, Imaging Sciences Division, 4th floor, Lambeth Wing, St Thomas' Hospital, London SE1 7EH, UK. E‐mail: giovanna.nordio@ 123456kcl.ac.uk
            Contributors
            giovanna.nordio@kcl.ac.uk
            Journal
            J Magn Reson Imaging
            J Magn Reson Imaging
            10.1002/(ISSN)1522-2586
            JMRI
            Journal of Magnetic Resonance Imaging
            John Wiley and Sons Inc. (Hoboken )
            1053-1807
            1522-2586
            02 February 2017
            July 2017
            : 46
            : 1 ( doiID: 10.1002/jmri.v46.1 )
            : 218-227
            28152227 5518207 10.1002/jmri.25575 JMRI25575
            © 2017 The Authors Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine

            This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

            Counts
            Figures: 8, Tables: 1, Pages: 10, Words: 5620
            Product
            Funding
            Funded by: the EPSRC Centre for Doctoral Training in Medical Imaging
            Award ID: EP/L015226/1
            Funded by: Philips Healthcare
            Funded by: Centre of Excellence in Medical Engineering funded by the Wellcome Trust and EPSRC
            Award ID: WT 088641/Z/09/Z
            Funded by: Department of Health via the National Institute for Health Research (NIHR)
            Funded by: St Thomas' NHS Foundation Trust in partnership with King's College London
            Funded by: King's College Hospital NHS Foundation Trust
            Categories
            Original Research
            Original Research
            Cardiac
            Custom metadata
            2.0
            jmri25575
            July 2017
            Converter:WILEY_ML3GV2_TO_NLMPMC version:5.1.4 mode:remove_FC converted:20.07.2017

            Radiology & Imaging

            t1 mapping, saturation‐recovery, mri, accuracy, precision

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