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 language | English (US) |
|---|---|
| Pages (from-to) | 775-782 |
| Number of pages | 8 |
| Journal | Journal of Magnetic Resonance Imaging |
| Volume | 8 |
| Issue number | 4 |
| DOIs | |
| State | Published - Jul 1998 |
| Externally published | Yes |
Fingerprint
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 journal › Article
}
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 -