Use, misuse, and abuse of apparent diffusion coefficients

Grebenkov, Denis S.

doi:10.1002/cmr.a.20152

Cited by 36 publications

(30 citation statements)

References 86 publications

(137 reference statements)

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“…It is uniquely a reflection of compartmentation. This example illustrates potential ambiguities of ADCs whose interpretation may be strongly misleading, as it was already stressed [20,56]. When the intermediate permeability is very small (W 1 = 10 À7 m/s), the signal attenuation, shown by green dash-dotted line, is close to the limiting case of W 1 = 0.…”

Section: The Role Of the Intermediate Permeabilitymentioning

confidence: 82%

Pulsed-gradient spin-echo monitoring of restricted diffusion in multilayered structures

Grebenkov

2010

Journal of Magnetic Resonance

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Section: The Role Of the Intermediate Permeabilitymentioning

confidence: 82%

Pulsed-gradient spin-echo monitoring of restricted diffusion in multilayered structures

Grebenkov

2010

Journal of Magnetic Resonance

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“…The microscopic signal from the intra-neurite compartment reads

h_{b}^{int} false(g, bold-italicω false) = \exp (- b {〈 g, bold-italicω 〉}^{2} normalλ),

where 0≤ λ ≤ λ free is the intrinsic diffusion coefficient parallel to the neurites and the upper bound λ free is given by the free-water diffusivity. Note that λ is an apparent (or effective) parameter that depends not only on the diffusion process in the underlying material but also on the MRI experiment, such as the temporal profile of the gradient sequence (Grebenkov, 2010). …”

Section: Methodsmentioning

confidence: 99%

Multi-compartment microscopic diffusion imaging

et al. 2016

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This paper introduces a multi-compartment model for microscopic diffusion anisotropy imaging. The aim is to estimate microscopic features specific to the intra- and extra-neurite compartments in nervous tissue unconfounded by the effects of fibre crossings and orientation dispersion, which are ubiquitous in the brain. The proposed MRI method is based on the Spherical Mean Technique (SMT), which factors out the neurite orientation distribution and thus provides direct estimates of the microscopic tissue structure. This technique can be immediately used in the clinic for the assessment of various neurological conditions, as it requires only a widely available off-the-shelf sequence with two b-shells and high-angular gradient resolution achievable within clinically feasible scan times. To demonstrate the developed method, we use high-quality diffusion data acquired with a bespoke scanner system from the Human Connectome Project. This study establishes the normative values of the new biomarkers for a large cohort of healthy young adults, which may then support clinical diagnostics in patients. Moreover, we show that the microscopic diffusion indices offer direct sensitivity to pathological tissue alterations, exemplified in a preclinical animal model of Tuberous Sclerosis Complex (TSC), a genetic multi-organ disorder which impacts brain microstructure and hence may lead to neurological manifestations such as autism, epilepsy and developmental delay.

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“…Analytic solution of the diffusion equation often benefits from the use of special techniques, e.g. the Laplace transform [9,10] calculus [11][12][13]. Nevertheless, the set of pore space geometries for which a compact analytic solution is feasible remains limited and includes only relatively simple geometries.…”

Section: Techniques For Calculation Of the Diffusion Propagatormentioning

confidence: 99%

Further development of discrete computational techniques for calculation of restricted diffusion propagators in porous media

Momot

Powell

Tourell

2015

Microporous and Mesoporous Materials

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a b s t r a c tMagnetic resonance is a well-established tool for structural characterisation of porous media. Features of pore-space morphology can be inferred from NMR diffusion-diffraction plots or the time-dependence of the apparent diffusion coefficient. Diffusion NMR signal attenuation can be computed from the restricted diffusion propagator, which describes the distribution of diffusing particles for a given starting position and diffusion time.We present two techniques for efficient evaluation of restricted diffusion propagators for use in NMR porous-media characterisation. The first is the Lattice Path Count (LPC). Its physical essence is that the restricted diffusion propagator connecting points A and B in time t is proportional to the number of distinct length-t paths from A to B. By using a discrete lattice, the number of such paths can be counted exactly. The second technique is the Markov transition matrix (MTM). The matrix represents the probabilities of jumps between every pair of lattice nodes within a single timestep. The propagator for an arbitrary diffusion time can be calculated as the appropriate matrix power. For periodic geometries, the transition matrix needs to be defined only for a single unit cell. This makes MTM ideally suited for periodic systems.Both LPC and MTM are closely related to existing computational techniques: LPC, to combinatorial techniques; and MTM, to the Fokker-Planck master equation. The relationship between LPC, MTM and other computational techniques is briefly discussed in the paper. Both LPC and MTM perform favourably compared to Monte Carlo sampling, yielding highly accurate and almost noiseless restricted diffusion propagators. Initial tests indicate that their computational performance is comparable to that of finite element methods. Both LPC and MTM can be applied to complicated pore-space geometries with no analytic solution. We discuss the new methods in the context of diffusion propagator calculation in porous materials and model biological tissues.

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Use, misuse, and abuse of apparent diffusion coefficients

Cited by 36 publications

References 86 publications

Pulsed-gradient spin-echo monitoring of restricted diffusion in multilayered structures

Pulsed-gradient spin-echo monitoring of restricted diffusion in multilayered structures

Multi-compartment microscopic diffusion imaging

Further development of discrete computational techniques for calculation of restricted diffusion propagators in porous media

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