Diffraction-like effects in NMR diffusion studies of fluids in porous solids

Callaghan, Paul T.; Coy, Andrew; MacGowan, David; Packer, Kenneth J.; Zelaya, Fernando

doi:10.1038/351467a0

Cited by 620 publications

(564 citation statements)

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“…In highly regular porous structures, such as packed beads, the echo attenuation will exhibit diffraction peaks and pore geometry information can be directly read from the peaks (Callaghan et al, 1991). However, diffraction patterns in biological systems have only been observed in packed erythrocytes and not in tissues such as multi-axonal systems, possibly due to structural heterogeneity as our simulations suggest.…”

Section: Discussion Estimating Mean Axon Diameter With Qsimentioning

confidence: 85%

“…QSI allows assessment of microarchitecture by exploiting the regularity of restrictions to molecular diffusion in porous systems as applied to determine pore geometry in porous solids (Callaghan et al, 1991), the study of packed erythrocytes (Torres et al, 1998), and the assessment of axonal architecture (Chin et al, 2004;Cohen and Assaf, 2002;Malmborg et al, 2006). In WM tracts, the porous system consists of water diffusion restricted by axon membranes and myelin sheaths (Beaulieu, 2002).…”

Section: Introductionmentioning

confidence: 99%

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Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

et al. 2008

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Q-space imaging (QSI), a diffusion MRI technique, can provide quantitative tissue architecture information at cellular dimensions not amenable by conventional diffusion MRI. By exploiting regularities in molecular diffusion barriers, QSI can estimate the average barrier spacing such as the mean axon diameter in white matter (WM). In this work, we performed ex vivo QSI on cervical spinal cord sections from healthy C57BL/6 mice at 400MHz using a custom-designed uniaxial 50T/m gradient probe delivering a 0.6 µm displacement resolution capable of measuring axon diameters on the scale of 1 µm. After generating QSI-derived axon diameter maps, diameters were calculated using histology from seven WM tracts (dorsal corticospinal, gracilis, cuneatus, rubrospinal, spinothalamic, reticulospinal, and vestibulospinal tracts) each with different axon diameters. We found QSI-derived diameters from regions drawn in the seven WM tracts (1.1 to 2.1 µm) to be highly correlated (r 2 = 0.95) with those calculated from histology (0.8 to 1.8 µm). The QSI-derived values overestimated those obtained by histology by approximately 20%, which is likely due to the presence of extracellular signal. Finally, simulations on images of synthetic circular axons and axons from histology suggest that QSI-derived diameters are informative despite diameter and axon shape variation and the presence of intra-cellular and extra-cellular signal. QSI may be able to quantify nondestructively changes in WM axon architecture due to pathology or injury at the cellular level.

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Section: Discussion Estimating Mean Axon Diameter With Qsimentioning

confidence: 85%

Section: Introductionmentioning

confidence: 99%

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

et al. 2008

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“…The normalized signal, E[G d , ⌬], following the application of such a diffusion-sensitizing gradient pair is given by (9,16,17),…”

Section: Q-space Theorymentioning

confidence: 99%

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

Shanbhag

Altes

Miller

et al. 2006

Magnetic Resonance Imaging

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Purpose:To examine the utility of a 3 He spectroscopic q-space technique for detecting changes in lung morphometry in vivo. Materials and Methods:A diffusion-weighted spectroscopy sequence was used to collect global diffusion data from healthy adults (N ϭ 11), healthy children (N ϭ 5), and chronic obstructive pulmonary disease (COPD) patients (N ϭ 2) using 40 cc of hyperpolarized 3 He gas within a two second breathhold. Displacement probability profiles (DPP) were obtained by Fourier transformation of diffusion data with respect to q. A bi-Gaussian model was used to decompose the DPPs into narrow and broad components, characterized by root-mean-square displacements X rms1 and X rms2 , respectively. Results:In healthy adults, the narrow component (X rms,1 ) of the DPP had a mean displacement of 188 Ϯ 10 m, slightly less than the reported average size of the alveoli. The broad component (X rms,2 ) had a mean value of 474 Ϯ 44 m, comparable to the diameter of the respiratory bronchioles in the acinus. In children, both X rms1 (167 Ϯ 4 m) and X rms2 (382 Ϯ 22 m) compared to healthy adults (P Ͻ 0.01). In COPD patients, the mean displacements were elevated (X rms1 : 265 Ϯ 71 m; X rms2 : 530 Ϯ 109 m) compared to healthy adults. Excellent correlation was found between rms displacements and age (age vs. X rms,1 : r ϭ 0.78, P Ͻ 0.001; age vs. X rms,2 : r ϭ 0.90, P Ͻ 0.001). Conclusion:The q-space parameters agreed remarkably well with published alveolar morphometry data. The results suggest that the technique may be sensitive to disease, as evident from the elevated mean displacements in COPD patients compared to healthy volunteers. Detailed lung microstructural information can be obtained using a very low volume of inhaled 3 He.

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“…As such, the signal attenuation curve (q-plot), is no longer linear with g 2 , even for single-component diffusion. When t is large enough for spins to completely sample the restrictions of a given pore, Ps reduces to the pore spin density function, ρ(r'), and the echo attenuation becomes the Fourier power spectrum of ρ(r') [5,24]. Specifically, for spins…”

Section: Methodsmentioning

confidence: 99%

Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

Mair

Wang

Rosen

et al. 2003

Magnetic Resonance Imaging

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We report initial NMR studies of continuous flow laser-polarized xenon gas, both in unrestricted tubing, and in a model porous media. The study uses Pulsed Gradient Spin Echo-based techniques in the gas-phase, with the aim of obtaining more sophisticated information than just translational selfdiffusion coefficients. Pulsed Gradient Echo studies of continuous flow laser-polarized xenon gas in unrestricted tubing indicate clear diffraction minima resulting from a wide distribution of velocities in the flow field. The maximum velocity experienced in the flow can be calculated from this minimum, and is seen to agree with the information from the complete velocity spectrum, or motion propagator, as well as previously published images. The susceptibility of gas flows to parameters such as gas mixture content, and hence viscosity, are observed in experiments aimed at identifying clear structural features from echo attenuation plots of gas flow in porous media. Gas-phase NMR scattering, or position correlation flow-diffraction, previously clearly seen in the echo attenuation data from laserpolarized xenon flowing through a 2 mm glass bead pack is not so clear in experiments using a different gas mixture. A propagator analysis shows most gas in the sample remains close to static, while a small portion moves through a presumably near-unimpeded path at high velocities.

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Diffraction-like effects in NMR diffusion studies of fluids in porous solids

Cited by 620 publications

References 7 publications

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy

Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

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Diffraction-like effects in NMR diffusion studies of fluids in porous solids

Cited by 620 publications

References 7 publications

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

Indirect measurement of regional axon diameter in excised mouse spinal cord with q-space imaging: Simulation and experimental studies

q‐space analysis of lung morphometry in vivo with hyperpolarized3He spectroscopy

Applications of controlled-flow laser-polarized xenon gas to porous and granular media study

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Product

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q‐space analysis of lung morphometry in vivo with hyperpolarized³He spectroscopy