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      3D SASHA myocardial T1 mapping with high accuracy and improved precision

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          Abstract

          Purpose

          To improve the precision of a free-breathing 3D saturation-recovery-based myocardial T1 mapping sequence using a post-processing 3D denoising technique.

          Methods

          A T1 phantom and 15 healthy subjects were scanned on a 1.5 T MRI scanner using 3D saturation-recovery single-shot acquisition (SASHA) for myocardial T1 mapping. A 3D denoising technique was applied to the native T1-weighted images before pixel-wise T1 fitting. The denoising technique imposes edge-preserving regularity and exploits the co-occurrence of 3D spatial gradients in the native T1-weighted images by incorporating a multi-contrast Beltrami regularization. Additionally, 2D modified Look-Locker inversion recovery (MOLLI) acquisitions were performed for comparison purposes. Accuracy and precision were measured in the myocardial septum of 2D MOLLI and 3D SASHA T1 maps and then compared. Furthermore, the accuracy and precision of the proposed approach were evaluated in a standardized phantom in comparison to an inversion-recovery spin-echo sequence (IRSE).

          Results

          For the phantom study, Bland–Altman plots showed good agreement in terms of accuracy between IRSE and 3D SASHA, both on non-denoised and denoised T1 maps (mean difference −1.4 ± 18.9 ms and −4.4 ± 21.2 ms, respectively), while 2D MOLLI generally underestimated the T1 values (69.4 ± 48.4 ms). For the in vivo study, there was a statistical difference between the precision measured on 2D MOLLI and on non-denoised 3D SASHA T1 maps ( P = 0.005), while there was no statistical difference after denoising ( P = 0.95).

          Conclusion

          The precision of 3D SASHA myocardial T1 mapping was substantially improved using a 3D Beltrami regularization based denoising technique and was similar to that of 2D MOLLI T1 mapping, while preserving the higher accuracy and whole-heart coverage of 3D SASHA.

          Electronic supplementary material

          The online version of this article (10.1007/s10334-018-0703-y) contains supplementary material, which is available to authorized users.

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          Most cited references 17

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

            Background 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. Materials and methods 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
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              Saturation recovery single-shot acquisition (SASHA) for myocardial T(1) mapping.

              To validate a new saturation recovery single-shot acquisition (SASHA) pulse sequence for T1 mapping and to compare SASHA T1 values in heart failure patients and healthy controls. The SASHA sequence consists of 10 electrocardiogram-triggered single-shot balanced steady-state free precession images in a breath-hold. The first image is acquired without magnetization preparation and the remaining nine images follow saturation pulses with variable saturation recovery times. SASHA was validated through Bloch equation simulations, Monte Carlo simulations, and phantom experiments. Pre- and postcontrast myocardial and blood T1 values were measured in 29 healthy volunteers and 7 patients with heart failure. SASHA T1 values had excellent agreement (bias, 5 ± 5 ms) with spin echo experiments in phantoms with a wide range of physiologic T1 and T2 values and its accuracy was independent of flip angle, absolute T1 , T2 , and heart rate. The average baseline myocardial T1 in heart failure patients was higher than in healthy controls (1200 ± 32 vs. 1170 ± 9 ms, P < 0.05) at 1.5T, as was the calculated blood-tissue partition coefficient, λ, (0.42 ± 0.04 vs. 0.38 ± 0.02, P < 0.05), consistent with diffuse myocardial fibrosis. The SASHA sequence is a simple and fast approach to in vivo T1 mapping with good accuracy in simulations and phantom experiments. Copyright © 2013 Wiley Periodicals, Inc.
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                Author and article information

                Affiliations
                [1 ]GRID grid.425213.3, School of Biomedical Engineering and Imaging Sciences, King’s College London, 4th Floor, Lambeth Wing, , St Thomas’ Hospital, ; London, SE1 7EH UK
                [2 ]ISNI 0000 0001 2157 0406, GRID grid.7870.8, Escuela de Ingeniería, Pontificia Universidad Católica de Chile, ; Santiago, Chile
                [3 ]ISNI 0000 0001 2194 6418, GRID grid.29172.3f, Imagerie Adaptive Diagnostique et Interventionnelle, INSERM et Université de Lorraine, ; Nancy, France
                [4 ]CIC-IT 1433, INSERM, Université de Lorraine, CHRU de Nancy, Nancy, France
                Contributors
                ORCID: http://orcid.org/0000-0002-7835-2992, giovanna.nordio@kcl.ac.uk
                aurelien.bustn@kcl.ac.uk
                markus.henningsson@kcl.ac.uk
                imran.1.rashid@kcl.ac.uk
                amedeo.chiribiri@kcl.ac.uk
                tevfik.ismail@kcl.ac.uk
                freddy.odille@inserm.fr
                claudia.prieto@kcl.ac.uk
                rene.botnar@kcl.ac.uk
                Journal
                MAGMA
                MAGMA
                Magma (New York, N.y.)
                Springer International Publishing (Cham )
                0968-5243
                1352-8661
                6 September 2018
                6 September 2018
                2019
                : 32
                : 2
                : 281-289
                30191345 6424941 703 10.1007/s10334-018-0703-y
                © The Author(s) 2018, corrected publication October 2018

                Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License ( http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

                Funding
                Funded by: EPSRC Centre for Doctoral training in Medical Imaging
                Award ID: EP/L015226/1
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/501100000266, Engineering and Physical Sciences Research Council;
                Award ID: EP/P001009/1
                Award ID: EP/P007619
                Award Recipient :
                Funded by: FundRef http://dx.doi.org/10.13039/100004440, Wellcome Trust;
                Award ID: WT/203148/Z/16/Z
                Award Recipient :
                Categories
                Research Article
                Custom metadata
                © European Society for Magnetic Resonance in Medicine and Biology (ESMRMB) 2019

                Radiology & Imaging

                cardiac mri, denoising, accuracy, precision, myocardial t1 mapping

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