Time-dependent diffusion magnetic resonance imaging: measurement, modeling, and applications

Journal of Zhejiang University. Science A, Journal Year: 2024, Volume and Issue: 25(10), P. 765 - 787

Published: Aug. 22, 2024

Language: Английский

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Cardiac q‐space trajectory imaging by motion‐compensated tensor‐valued diffusion encoding in human heart in vivo

Magnetic Resonance in Medicine, Journal Year: 2023, Volume and Issue: 90(1), P. 150 - 165

Published: March 20, 2023

Purpose Tensor‐valued diffusion encoding can probe more specific features of tissue microstructure than what is available by conventional weighting. In this work, we investigate the technical feasibility tensor‐valued at high b ‐values with q‐space trajectory imaging (QTI) analysis, in human heart vivo. Methods Ten healthy volunteers were scanned on a 3T scanner. We designed time‐optimal gradient waveforms for (linear and planar) second‐order motion compensation. Data analyzed QTI. Normal values repeatability investigated mean diffusivity (MD), fractional anisotropy (FA), microscopic FA (μFA), isotropic, anisotropic total kurtosis (MKi, MKa, MKt), orientation coherence ( C c ). A phantom, consisting two fiber blocks adjustable angles, was used to evaluate sensitivity parameters dispersion time. Results QTI data left ventricular myocardium MD = 1.62 ± 0.07 μm 2 /ms, 0.31 0.03, μFA 0.43 0.07, MKa 0.20 MKi 0.13 MKt 0.33 0.09, 0.56 0.22 (mean SD across subjects). Phantom experiments showed that depends dispersion, whereas insensitive effect. Conclusion demonstrated first analysis vivo, along measurements myocardial μFA, MKi, . The methodology technically feasible provides promising novel biomarkers characterization.

Language: Английский

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Tuned exchange imaging: Can the filter exchange imaging pulse sequence be adapted for applications with thin slices and restricted diffusion?

NMR in Biomedicine, Journal Year: 2024, Volume and Issue: 37(11)

Published: July 4, 2024

Filter exchange imaging (FEXI) is a double diffusion-encoding (DDE) sequence that specifically sensitive to between sites with different apparent diffusivities. FEXI uses filtering block followed by detection at varying mixing times map the rate. Long enhance sensitivity exchange, but they pose challenges for applications require stimulated echo crusher gradients. Thin slices strong crushers, which can introduce significant diffusion weighting and bias rate estimates. Here, we treat crushers as an additional encoding consider triple sequence. This allows be corrected in case of multi-Gaussian diffusion, not easily presence restricted diffusion. Our approach addresses relies on ability independently gauge sensitivities arbitrary gradient waveforms. It follows two principles: (i) effects are included forward model using signal cumulant expansion; (ii) timing parameters gradients filter blocks adjusted maintain same level restriction regardless time. results tuned (TEXI) protocol. The accuracy mapping TEXI was assessed through Monte Carlo simulations spheres identical sizes gamma-distributed sizes, parallel hexagonally packed cylinders. demonstrate provides consistent rates slice thickness size, even crushers. However, depends b-values, times, geometry. constraints limitations discussed, including suggestions protocol adaptations. Further studies needed optimize precision assess experimentally realistic, heterogeneous substrates.

Language: Английский

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Revealing membrane integrity and cell size from diffusion kurtosis time dependence

Magnetic Resonance in Medicine, Journal Year: 2024, Volume and Issue: unknown

Published: Oct. 29, 2024

Abstract Purpose The nonmonotonic dependence of diffusion kurtosis on time has been observed in biological tissues, yet its relation to membrane integrity and cellular geometry remains be clarified. Here we establish explain the characteristic asymmetric shape peak. We also derive between peak , when reaches maximum, tissue parameters. Methods position qualitatively follow from adiabatic extension Kärger model onto case intra‐cellular diffusivity time‐dependence. This intuition is corroborated by effective medium theory‐based calculation, as well Monte Carlo simulations exchange randomly densely packed spheres for various values permeability, cell fractions sizes, intrinsic diffusivity. Results that proportional geometric mean two scales: extra‐cellular correlation (determined size) residence permeability). When barrier‐limited, approaches a universal scaling form determined ratio . Conclusion Numerical theory provide an interpretation specific feature time‐dependence, offering potential biomarker vivo evaluation pathology disentangling functional (permeability) structural (cell tissues. relevant time‐dependent cumulants are sensitive pathological changes structure diseases, such ischemic stroke, tumors, Alzheimer's disease.

Language: Английский

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Ultra-strong diffusion-weighted MRI reveals cerebellar grey matter abnormalities in movement disorders

NeuroImage Clinical, Journal Year: 2023, Volume and Issue: 38, P. 103419 - 103419

Published: Jan. 1, 2023

Structural brain MRI has proven invaluable in understanding movement disorder pathophysiology. However, most work focused on grey/white matter volumetric (macrostructural) and white microstructural effects, limiting of frequently implicated grey differences. Using ultra-strong spherical tensor encoding diffusion-weighted MRI, a persistent signal was seen healthy cerebellar even at high diffusion-weightings (b ​≥ 10,000 s/mm2). Quantifying the proportion this (denoted fs), previously ascertained to originate from inside small spaces, provides potential proxy for cell body density. In work, approach applied first time clinical cohort, including patients with diagnosed disorders which cerebellum been symptom Five control participants (control group 1, median age 24.5 years (20–39 years), imaged two timepoints, demonstrated consistency measurement all three measures - MD (Mean Diffusivity) fs, Ds (dot diffusivity)- intraclass correlation coefficients (ICC) 0.98, 0.86 0.76, respectively. Comparison an older 2 (n = 5), 51 (43–58 years)) found no significant differences, neither morphometric nor (MD (p 0.36), fs 0.17) 0.22)) measures. The cohort (Parkinson's Disease, n 5, dystonia, 5. Spinocerebellar Ataxia 6, 5) when compared age-matched (Control Group 2) identified significantly lower < 0.0001 p 0.0001) higher values SCA6 dystonia cohorts Lobar division these same differences superior inferior posterior lobes, while were either anterior lobes or measurements. contrast more conventional diffusion imaging, framework enhanced specificity restricted spaces (including cells) by eliminating signals cerebrospinal fluid axons. context human animal histopathology studies, findings potentially implicate Purkinje granule cells as contributors observed both types having several neurological through postmortem model studies. This novel imaging shows promise improving diagnosis, prognosis, treatment.

Language: Английский

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On the sampling strategies and models for measuring diffusion exchange with a double diffusion encoding sequence

Magnetic Resonance Letters, Journal Year: 2023, Volume and Issue: 3(3), P. 232 - 247

Published: June 18, 2023

Water exchange between the different compartments of a heterogeneous specimen can be characterized via diffusion magnetic resonance imaging (dMRI). Many analysis frameworks using dMRI data have been proposed to describe exchange, often double encoding (DDE) stimulated echo sequence. Techniques such as weighted (DEWI) and filter rapid models, use specific subset full space DDE signal. In this work, general representation signal was employed with sampling schemes (namely constant b1, diagonal anti-diagonal) from reduction models estimate exchange. A near-uniform scheme compared other schemes. The were also applied their own subsampling These on both simulated experimental acquired benchtop MR scanner. synthetic data, performed best due consistency estimates ground truth. shifted outperformed others, yielding most consistent estimation. results suggest feasibility measuring along variable future studies, algorithms could further developed for optimization schemes, well incorporating additional properties, geometry anisotropy, into frameworks.

Language: Английский

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DPP: deep phase prior for parallel imaging with wave encoding

Physics in Medicine and Biology, Journal Year: 2024, Volume and Issue: 69(10), P. 105013 - 105013

Published: April 12, 2024

In Magnetic Resonance (MR) parallel imaging with virtual channel-expanded Wave encoding, limitations are imposed on the ability to comprehensively and accurately characterize background phase. These primarily attributed calibration process relying solely center low-frequency Auto-Calibration Signals (ACS) data for calibration.

Language: Английский

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Restriction-Induced Time-Dependent Transcytolemmal Water Exchange: Revisiting the Kӓrger Exchange Model

Published: Jan. 1, 2024

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Language: Английский

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The interplay between exchange and microscopic kurtosis as measured by diffusion MRI with double diffusion encoding: Theory and simulations

Research Square (Research Square), Journal Year: 2024, Volume and Issue: unknown

Published: July 29, 2024

Double diffusion encoding (DDE) makes MRI sensitive to a wide range of microstructural features, and the acquired data can be analysed using different approaches. Correlation tensor imaging (CTI) uses DDE resolve three components diffusional kurtosis: isotropic, anisotropic, microscopic. The microscopic kurtosis is estimated from contrast between single (SDE) parallel signals at same b-value. Another approach multi-Gaussian exchange (MGE), which employs measure exchange. Sensitivity obtained by contrasting SDE CTI MGE exploit signal quantify exchange, this study investigates interplay these two quantities. We perform Monte-Carlo simulations in geometries with varying levels behaviour parameters MGE. conclude that rate. In an attempt separate we propose heuristic representation referred as µMGE (MGE incorporating kurtosis) accounts for both effects, exploiting distinct signatures mixing time: causes dependence on time while does not. find applying multiple times orthogonal allows estimation well all sources kurtosis.

Language: Английский

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The Diffusion Exchange Ratio (DEXR): A minimal sampling of diffusion exchange spectroscopy to probe exchange, restriction, and time-dependence

bioRxiv (Cold Spring Harbor Laboratory), Journal Year: 2024, Volume and Issue: unknown

Published: Aug. 6, 2024

Abstract Water exchange is increasingly recognized as an important biological process that can affect the study of tissue using diffusion MR. Methods to measure exchange, however, remain immature opposed those used characterize restriction, with no consensus on optimal pulse sequence(s) or signal model(s). In general, trend has been towards data-intensive fitting highly parameterized models. We take opposite approach and show a judicious sub-sample spectroscopy (DEXSY) data be robustly quantify well in data-efficient manner. This sampling produces ratio two points per mixing time: (i) one point equal weighting both encoding periods, which gives maximal contrast, (ii) same total just first period, for normalization. call this quotient Diffusion EXchange Ratio (DEXR). Furthermore, we it probe time-dependent by estimating velocity autocorrelation function (VACF) over intermediate long times (∼ 2 − 500 ms). provide comprehensive theoretical framework design DEXR experiments case static constant gradients. Data from Monte Carlo simulations acquired fixed viable ex vivo neonatal mouse spinal cord permanent magnet system are presented test validate approach. cord, report following apparent parameters 6 points: τ k = 17 ± 4 ms, f NG 0.71 0.01, R eff 1.10 0.01 μ m, 0.21 0.06 m/ms, correspond time, restricted non-Gaussian fraction, effective spherical radius, permeability, respectively. For VACF, long-time, power-law scaling ≈ t 2.4 , approximately consistent disordered domains 3-D. Overall, method shown efficient, capable providing valuable quantitative metrics minimal MR data.

Language: Английский

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