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High b-value q-space analyzed diffusion-weighted MRS and MRI in neuronal tissues – a technical review

  1. Yoram Cohen1,*,
  2. Yaniv Assaf1,2

Article first published online: 5 DEC 2002

DOI: 10.1002/nbm.778

Issue

NMR in Biomedicine

NMR in Biomedicine

Special Issue: Diffusion tensor imaging and axonal mapping - state of the art

Volume 15, Issue 7-8, pages 516–542, November - December 2002

Additional Information

How to Cite

Cohen, Y. and Assaf, Y. (2002), High b-value q-space analyzed diffusion-weighted MRS and MRI in neuronal tissues – a technical review. NMR Biomed., 15: 516–542. doi: 10.1002/nbm.778

Author Information

  1. 1

    School of Chemistry, The Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv, 69978, Israel

  2. 2

    Wohl Institute for Advanced Imaging, Tel Aviv Sourasky Medical Center, Tel Aviv, 64239, Israel

*School of Chemistry, The Sackler Faculty of Exact Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel

Publication History

  1. Issue published online: 5 DEC 2002
  2. Article first published online: 5 DEC 2002
  3. Manuscript Accepted: 10 FEB 2002
  4. Manuscript Revised: 25 DEC 2001
  5. Manuscript Received: 16 MAY 2001

Funded by

  • United States–Israel Binational and Foundation 97-00346

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Keywords:

  • diffusion MRI;
  • high b-value DWI;
  • q-space diffusion;
  • white matter disorders;
  • multiple sclerosis;
  • MS;
  • spinal cord trauma;
  • neuronal degeneration;
  • neuronal maturation

Abstract

  1. Top of page
  2. Abstract
  3. REFERENCES

This review deals with high b-value q-space diffusion-weighted MRI (DW-MRI) of neuronal tissues. It is well documented that at sufficiently high b-values (and high q-values) neuronal water signal decay in diffusion experiments is not mono-exponential. This implies the existence of more than one apparent diffusing component or evidence for restriction. The assignment of the different apparent diffusing components to real physical entities is not straightforward. However, the apparent slow diffusing component that was found to be restricted to a compartment of a few microns, if originating mainly from a specific pool and if assigned correctly, may potentially be used to obtain more specific MR images with regard to specific pathologies of the CNS. This review examines the utility of analyzing high b-value diffusion MRS and MRI data using the q-space approach introduced by Callaghan and by Cory and Garroway. This approach provides displacement probability maps that emphasize, at long diffusion times, the characteristics of the apparent slow diffusing component. Examples from excised spinal cord, where the experimental conditions for which the q-space analysis of MR diffusion data was developed can be met or approached will be presented. Then examples from human MS patients, where q-space requirement for the short gradient pulse is clearly violated, are presented. In the excised spinal cord studies, this approach was used to study spinal cord maturation and trauma, and was found to be more sensitive than other conventional methods in following spinal cord degeneration in an experimental model of vascular dementia (VaD). High b-value q-space DWI was also recently used to study healthy and MS diseased human brains. This approach was found to be very sensitive to the disease load in MS, compared with other conventional MRI methods, especially in the normal appearing white matter (NAWM) of MS brains. Finally, the potential diagnostic capacity embedded in high b-value q-space analyzed diffusion MR images is discussed. The potentials and caveats of this approach are outlined and experimental data are presented that show the effect of violating the short gradient pulse (SGP) approximation on the extracted parameters from the q-space analysis. Copyright © 2002 John Wiley & Sons, Ltd.

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Abbreviations used:
ADC

apparent diffusion coefficient

CNS

central nervous system

CSF

cerebral spinal fluid

DW-MRS

diffusion weighted magnetic resonance spectroscopy

DWI

diffusion-weighted imaging

DTI

diffusion tensor imaging

EAE

experimental allergic encephalomyelitis

EAN

experimental allergic neuritis

EM

electron microscopy

EPI

echo planar imaging

FA

fractional anisotropy

FLAIR

fluid attenuated inversion recovery

FT

Fourier transform

MR

magnetic resonance

MRI

magnetic resonance imaging

MRS

magnetic resonance spectroscopy

MS

multiple sclerosis

MT

magnetization transfer

NAWM

normal appearing white matter

PNS

peripheral nervous system

ROI

region of interest

SD

standard deviation

SNR

signal to noise ratio

SGP

short gradient pulse

SP-SHR

stroke-prone spontaneous hypertensive rat

TE

time to echo

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