Novel insights into in‐vivo diffusion tensor cardiovascular magnetic resonance using computational modelling and a histology‐based virtual microstructure

Rose, Jan N; Nielles‐Vallespin, Sonia; Ferreira, Pedro F.; Firmin, David N.; Scott, Andrew D.; Doorly, D. J.

doi:10.1002/mrm.27561

Cited by 21 publications

(30 citation statements)

References 68 publications

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“…In the ex vivo measurements, it was noted that the MDs increased by 2% and 10%, respectively (baseline) for first‐ and second‐order gradient moment compensation compared to SE‐M0, which was also found in simulations of the SE‐M0 and SE‐M2 gradient waveforms . Detailed data analysis revealed that this increase is primarily driven by increased measured diffusivity along the secondary and tertiary eigenvectors, whereas diffusivity along the primary eigenvector agreed well.…”

Section: Discussionsupporting

confidence: 52%

On probing intravoxel incoherent motion in the heart‐spin‐echo versus stimulated‐echo DWI

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Stoeck

Mathez

et al. 2019

Magnetic Resonance in Med

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Purpose: Mapping intravoxel incoherent motion (IVIM) in the heart remains challenging despite advances in cardiac DWI and DTI. In the present work, simulations and experimental imaging are used to compare the IVIM encoding efficiency of spinecho-and stimulated-echo-based DWI/DTI for assessing myocardial perfusion. Methods: Using normalized phase distributions and statistical models of capillary networks derived from histological studies, along with typical diffusion gradient waveforms for in vivo cardiac DWI/DTI, Monte Carlo simulations were performed. The simulation results were compared to IVIM measurements of perfused porcine hearts regarding both magnitude and phase modulation. An IVIM tensor model was used to account for anisotropy of the capillary network, and potential bias of parameter estimation was reported based on simulations. Results: Both computer simulations and experimental data demonstrate a low sensitivity of spin-echo DWI/DTI sequences for IVIM parameters, whereas stimulatedecho-based DWI/DTI with typical mixing times can differentiate between no-flow baseline and perfused myocardium (+129% IVIM-derived flow). In addition, ischemic territories induced by coronary occlusion could be successfully detected. With increasing order of motion compensation (M0/M1/M2) of the diffusion encoding gradients, as required for cardiac in vivo spin-echo DWI/DTI, the low IVIM sensitivity of spin-echo DWI/DTI decreased further in simulations: maximum attenuations of perfusion compartment 52/13/5% (b = 500 s/mm 2 ). Conclusion: Given the short encoding time of spin-echo-based DWI/DTI sequences, a limited perfusion sensitivity results, in particular in combination with motioncompensated diffusion gradients. In contrast, stimulated-echo based DWI/DTI has the potential to identify perfusion changes in cardiac IVIM in vivo. K E Y W O R D S DWI, intravoxel incoherent motion, motion-compensated spin-echo, myocardial perfusion, perfused heart, STEAM F I G U R E 2 Gradient shapes, 0th moments, and integrals of the 0th moment. Normalized effective gradient shapes of Stejskal-Tanner SE-DWI (M0, red), first-order motion-compensated SE-DWI (M1, green), second-order motion-compensated SE-DWI (M2, blue), and STEAM-DWI (orange). The normalized time on the x-axis corresponds to the timing used in the simulations and ex vivo studies. The bottom row shows the integral of the 0th gradient moment (multiplied by the normalized b-value), which is used for generation of phase distributions M0,

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Section: Discussionsupporting

confidence: 52%

On probing intravoxel incoherent motion in the heart‐spin‐echo versus stimulated‐echo DWI

Spinner

Stoeck

Mathez

et al. 2019

Magnetic Resonance in Med

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“…This has been reported before both in vivo and ex vivo [3,12,28]. The higher MD and lower FA values obtained using M2-SE reflect the shorter diffusion time and, therefore, fewer interactions between water molecules and microstructural barriers as demonstrated in recent simulation work [29]. Whilst these differences between sequences were only statistically significant for systole in this study, the trend was present in diastole and lack of statistical significance may reflect the small numbers in this group.…”

Section: Discussionsupporting

confidence: 77%

Diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy: a comparison of motion-compensated spin echo and stimulated echo techniques

Khalique

Scott

Ferreira

et al. 2019

Magn Reson Mater Phy

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Objectives Diffusion tensor cardiovascular magnetic resonance (DT-CMR) interrogates myocardial microstructure. Two frequently used in vivo DT-CMR techniques are motion-compensated spin echo (M2-SE) and stimulated echo acquisition mode (STEAM). Whilst M2-SE is strain-insensitive and signal to noise ratio efficient, STEAM has a longer diffusion time and motion compensation is unnecessary. Here we compare STEAM and M2-SE DT-CMR in patients. Materials and methods Biphasic DT-CMR using STEAM and M2-SE, late gadolinium imaging and pre/post gadolinium T1-mapping were performed in a mid-ventricular short-axis slice, in ten hypertrophic cardiomyopathy (HCM) patients at 3 T. Results Adequate quality data were obtained from all STEAM, but only 7/10 (systole) and 4/10 (diastole) M2-SE acquisitions. Compared with STEAM, M2-SE yielded higher systolic mean diffusivity (MD) (p = 0.02) and lower fractional anisotropy (FA) (p = 0.02, systole). Compared with segments with neither hypertrophy nor late gadolinium, segments with both had lower systolic FA using M2-SE (p = 0.02) and trend toward higher MD (p = 0.1). The negative correlation between FA and extracellular volume fraction was stronger with STEAM than M2-SE (r 2 = 0.29, p < 0.001 STEAM vs. r 2 = 0.10, p = 0.003 M2-SE). Discussion In HCM, only STEAM reliably assesses biphasic myocardial microstructure. Higher MD and lower FA from M2-SE reflect the shorter diffusion times. Further work will relate DT-CMR parameters and microstructural changes in disease.

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“…STEAM sequences accommodate longer diffusion times, but also necessitate more complex simulations of the sequence because the magnetization does not remain solely in the transverse plane. Here, we use a simplified version of the STEAM sequence that ignores relaxation effects . If relaxation is ignored in the PGSE sequence, then it also reduces to this simplified STEAM sequence, so we refer to the latter as a generalized diffusion‐weighted sequence.…”

Section: Methodsmentioning

confidence: 99%

“…Here, we use a simplified version of the STEAM sequence that ignores relaxation effects. 21 If relaxation is ignored in the PGSE sequence, then it also reduces to this simplified STEAM sequence, so we refer to the latter as a generalized diffusion-weighted sequence. This generalized sequence allows a wider range of diffusion times, and is introduced here to examine the effect of longer diffusion times on the sensitivity analysis.…”

Section: Pulse Sequence Parameterizationmentioning

confidence: 99%

Global sensitivity analysis of skeletal muscle dMRI metrics: Effects of microstructural and pulse parameters

Naughton

Georgiadis

2019

Magnetic Resonance in Med

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Purpose: Estimating microstructural parameters of skeletal muscle from diffusion MRI (dMRI) signal requires understanding the relative importance of both microstructural and dMRI sequence parameters on the signal. This study seeks to determine the sensitivity of dMRI signal to variations in microstructural and dMRI sequence parameters, as well as assess the effect of noise on sensitivity. Methods: Using a cylindrical myocyte model of skeletal muscle, numerical solutions of the Bloch-Torrey equation were used to calculate global sensitivity indices of dMRI metrics (FA, RD, MD, λ 1 , λ 2 , λ 3) for wide ranges of microstructural and dMRI sequence parameters. The microstructural parameters were: myocyte diameter, volume fraction, membrane permeability, intra-and extracellular diffusion coefficients, and intra-and extracellular T 2 times. Two separate pulse sequences were examined, a PGSE and a generalized diffusion-weighted sequence that accommodates a larger range of diffusion times. The effect of noise and signal averaging on the sensitivity of the dMRI metrics was examined by adding synthetic noise to the simulated signal. Results: Among the examined parameters, the intracellular diffusion coefficient has the strongest effect, and myocyte diameter is more influential than permeability for FA and RD. The sensitivity indices do not vary significantly between the two pulse sequences. Also, noise strongly affects the sensitivity of the dMRI signal to microstructural variations. Conclusions: With the identification of key microstructural features that affect dMRI measurements, the reported sensitivity results can help interpret dMRI measurements of skeletal muscle in terms of the underlying microstructure and further develop parsimonious dMRI models of skeletal muscle.

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Novel insights into in‐vivo diffusion tensor cardiovascular magnetic resonance using computational modelling and a histology‐based virtual microstructure

Cited by 21 publications

References 68 publications

On probing intravoxel incoherent motion in the heart‐spin‐echo versus stimulated‐echo DWI

On probing intravoxel incoherent motion in the heart‐spin‐echo versus stimulated‐echo DWI

Diffusion tensor cardiovascular magnetic resonance in hypertrophic cardiomyopathy: a comparison of motion-compensated spin echo and stimulated echo techniques

Global sensitivity analysis of skeletal muscle dMRI metrics: Effects of microstructural and pulse parameters

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