Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter

John Ford, David B. Hackney, Ehud Lavi, Micheal Phillips, Upen Patel

Research output: Contribution to journalArticle

77 Citations (Scopus)

Abstract

We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 μsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 μm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-μm and 11-μm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.

Original languageEnglish (US)
Pages (from-to)775-782
Number of pages8
JournalJournal of Magnetic Resonance Imaging
Volume8
Issue number4
DOIs
StatePublished - Jul 1998
Externally publishedYes

Fingerprint

Permeability
Spinal Cord
Membranes
White Matter
Axons
Leukoencephalopathies

Keywords

  • Diffusion, MR
  • Spinal cord
  • White matter

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter. / Ford, John; Hackney, David B.; Lavi, Ehud; Phillips, Micheal; Patel, Upen.

In: Journal of Magnetic Resonance Imaging, Vol. 8, No. 4, 07.1998, p. 775-782.

Research output: Contribution to journalArticle

@article{326b66100cee44b09351b2a01dec638e,
title = "Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter",
abstract = "We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 μsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 μm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-μm and 11-μm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.",
keywords = "Diffusion, MR, Spinal cord, White matter",
author = "John Ford and Hackney, {David B.} and Ehud Lavi and Micheal Phillips and Upen Patel",
year = "1998",
month = "7",
doi = "10.1002/jmri.1880080405",
language = "English (US)",
volume = "8",
pages = "775--782",
journal = "Journal of Magnetic Resonance Imaging",
issn = "1053-1807",
publisher = "John Wiley and Sons Inc.",
number = "4",

}

TY - JOUR

T1 - Dependence of apparent diffusion coefficients on axonal spacing, membrane permeability, and diffusion time in spinal cord white matter

AU - Ford, John

AU - Hackney, David B.

AU - Lavi, Ehud

AU - Phillips, Micheal

AU - Patel, Upen

PY - 1998/7

Y1 - 1998/7

N2 - We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 μsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 μm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-μm and 11-μm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.

AB - We used a numerical simulation of water self-diffusion among permeable cylinders to predict the dependence of MR-based apparent diffusion coefficients in white matter on axonal separation, barrier permeability, and diffusion time (T). The transverse apparent diffusion coefficient (tADC), calculated with simulated diffusion-sensitizing gradients perpendicular to the axon fibers, remains a function of T down to diffusion times as short as .1 μsec for a range of diffusion barrier permeability. As the diffusion time lengthens, the response of tADC depends on axon diameter, with decreases in tADC occurring earliest, and most dramatically, for the smallest fiber diameter simulated (2 μm). For a given axonal separation, asymptotic values of ADC are determined by permeability alone and are the same for 2-μm and 11-μm fibers of equal membrane permeability. The effect of increased relative intracellular volume is manifested primarily in a decrease in tADC at short T. Increases in interaxonal spacing increase the tADC at asymptotically long diffusion times and reduce the dependence on permeability. However, at the widest plausible axonal separations, permeability remains an important determinant of tADC. These simulations may enhance interpretation of measured tADC in the context of the underlying physiologic and structural changes at the cellular level that accompany white-matter disease.

KW - Diffusion, MR

KW - Spinal cord

KW - White matter

UR - http://www.scopus.com/inward/record.url?scp=0031850504&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0031850504&partnerID=8YFLogxK

U2 - 10.1002/jmri.1880080405

DO - 10.1002/jmri.1880080405

M3 - Article

C2 - 9702877

AN - SCOPUS:0031850504

VL - 8

SP - 775

EP - 782

JO - Journal of Magnetic Resonance Imaging

JF - Journal of Magnetic Resonance Imaging

SN - 1053-1807

IS - 4

ER -