The effect of the rotational angle on MR diffusion indices in nerves: Is the rms displacement of the slow-diffusing component a good measure of fiber orientation?

Bar‐Shir, Amnon; Cohen, Yoram

doi:10.1016/j.jmr.2007.10.007

Cited by 7 publications

(4 citation statements)

References 42 publications

(88 reference statements)

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“…In most cases, when the pores are characterized by a continuous size distribution, the signal decay is characterized by a featureless nonmonoexponential decay. 41,48 The q-space approach, which enables extraction of fast and slow components from the Fourier transform of the signal decay may provide an estimate towards the relative mean size of pores and their orientation due to accentuation of the slow component; 41,70 nevertheless, it does not provide estimates or signatures for the width of the size distributions. Properties of the size distributions may be extremely important to derive: in neuronal tissue, emulsions, rocks, and other applications, the size distribution may be of importance in characterizing the specimen in question.…”

Section: Discussionmentioning

confidence: 99%

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

Shemesh

Özarslan

Basser

et al. 2010

The Journal of Chemical Physics

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NMR observable nuclei undergoing restricted diffusion within confining pores are important reporters for microstructural features of porous media including, inter-alia, biological tissues, emulsions and rocks. Diffusion NMR, and especially the single-pulsed field gradient ͑s-PFG͒ methodology, is one of the most important noninvasive tools for studying such opaque samples, enabling extraction of important microstructural information from diffusion-diffraction phenomena. However, when the pores are not monodisperse and are characterized by a size distribution, the diffusion-diffraction patterns disappear from the signal decay, and the relevant microstructural information is mostly lost. A recent theoretical study predicted that the diffusion-diffraction patterns in double-PFG ͑d-PFG͒ experiments have unique characteristics, such as zero-crossings, that make them more robust with respect to size distributions. In this study, we theoretically compared the signal decay arising from diffusion in isolated cylindrical pores characterized by lognormal size distributions in both s-PFG and d-PFG methodologies using a recently presented general framework for treating diffusion in NMR experiments. We showed the gradual loss of diffusion-diffraction patterns in broadening size distributions in s-PFG and the robustness of the zero-crossings in d-PFG even for very large standard deviations of the size distribution. We then performed s-PFG and d-PFG experiments on well-controlled size distribution phantoms in which the ground-truth is well-known a priori. We showed that the microstructural information, as manifested in the diffusion-diffraction patterns, is lost in the s-PFG experiments, whereas in d-PFG experiments the zero-crossings of the signal persist from which relevant microstructural information can be extracted. This study provides a proof of concept that d-PFG may be useful in obtaining important microstructural features in samples characterized by size distributions.

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Section: Discussionmentioning

confidence: 99%

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

Shemesh

Özarslan

Basser

et al. 2010

The Journal of Chemical Physics

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“…Exact solutions have been derived for idealized geometries [23][24][25][26] and some of these solutions were verified experimentally [22]. Several studies have shown how variation of experimental parameters affects the compartment size that was extracted, including variation of d, D and the rotational angle in both phantoms and neuronal tissue [21,22,27,28], however, the need to apply very strong gradients limits the ability to probe the finest spatial dimensions using high q experiments.…”

Section: Introductionmentioning

confidence: 92%

Measuring small compartmental dimensions with low-q angular double-PGSE NMR: The effect of experimental parameters on signal decay

Shemesh

Özarslan

Basser

et al. 2009

Journal of Magnetic Resonance

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“…Another useful property of the q-space approach in these cases is that the fast diffusing components of the signal decay can be suppressed by using very long Δ, and slowly diffusing components can be accentuated. For example, the slow component extracted from excised optic nerve was shown to provide a good estimate of the mean axon sizes, as well as an accurate means of extracting the directionality of the fiber (41,42). The q-space approach, reviewed in this issue (43) has been shown to indeed provide complementary microstructural information to DTI, and was used in a variety of applications such as studies of myelin deficient rats (44,45) detection of multiple sclerosis (MS) (24,46), and even differentiation between vascular dementia and Alzheimer’s disease (47).…”

Section: Introductionmentioning

confidence: 99%

From single‐pulsed field gradient to double‐pulsed field gradient MR: gleaning new microstructural information and developing new forms of contrast in MRI

et al. 2010

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One of the hallmarks of diffusion NMR and MRI is its ability to employ restricted diffusion to probe compartments much smaller than the excited volume or the MRI voxel, respectively, and extract microstructural information from them. Indeed, the single-pulsed-field-gradient (s-PFG) MR methodologies are employed with great success to probe microstructures in various disciplines ranging from chemistry to neuroscience. However, s-PFG MR also suffers from inherent shortcomings, especially when specimens are characterized by orientation or size distributions. In such cases, the microstructural information available from s-PFG experiments is limited or lost. The double-PFG (d-PFG) MR methodology, an extension of s-PFG MR, has attracted attention owing to recent theoretical studies predicting that it can overcome some inherent limitations of s-PFG MR. In this review, we survey the microstructural features that can be obtained from conventional s-PFG methods in the different q-regimes, as well as the limitations of these methodologies. The experimental aspects of the d-PFG methodology are then presented, along with an overview of its theoretical underpinnings and a general framework for relating the MR signal decay and material microstructure. We will describe the new microstructural features that can be obtained using the d-PFG MR framework. We then discuss recent studies that validated the new theoretical framework using phantoms in which the ground-truth is well known a priori, a crucial step prior to application of d-PFG in neuronal tissue. The experimental findings are in excellent agreement with the theoretical predictions and reveal, inter alia, zero-crossings of the signal decay, enhanced sensitivity towards size distributions, and angular dependencies of the signal decay from which accurate microstructural parameters such as compartment size, and even shape can be extracted. Finally, we show some initial findings in d-PFG imaging. This review lays the foundation for future studies, in which accurate and novel microstructural information could be extracted from complex biological specimens, eventually leading to new contrasts in MRI.

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The effect of the rotational angle on MR diffusion indices in nerves: Is the rms displacement of the slow-diffusing component a good measure of fiber orientation?

Cited by 7 publications

References 42 publications

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

Measuring small compartmental dimensions with low-q angular double-PGSE NMR: The effect of experimental parameters on signal decay

From single‐pulsed field gradient to double‐pulsed field gradient MR: gleaning new microstructural information and developing new forms of contrast in MRI

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