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

Noam Shemesh, Evren Özarslan, Peter J. Basser, Yoram Cohen*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

In confined geometries, the MR signal attenuation obtained from single pulsed gradient spin echo (s-PGSE) experiments reflects the dimension of the compartment, and in some cases, its geometry. However, to measure compartment size, high q-values must be applied, requiring high gradient strengths and/or long pulse durations and diffusion times. The angular double PGSE (d-PGSE) experiment has been proposed as a means to extract dimensions of confined geometries using low q-values. In one realization of the d-PGSE experiment, the first gradient pair is fixed along the x-axis, and the orientation of the second gradient pair is varied in the X-Y plane. Such a measurement is sensitive to microscopic anisotropy induced by the boundaries of the restricting compartment, and allows extraction of the compartment dimension. In this study, we have juxtaposed angular d-PGSE experiments and simulations to extract sizes from well-characterized NMR phantoms consisting of water filled microcapillaries. We are able to accurately extract sizes of small compartments (5 μm) using the angular d-PGSE experiment even when the short gradient pulse (SGP) approximation is violated and over a range of mixing and diffusion times. We conclude that the angular d-PGSE experiment may fill an important niche in characterizing compartment sizes in which restricted diffusion occurs.

Original languageEnglish
Pages (from-to)15-23
Number of pages9
JournalJournal of Magnetic Resonance
Volume198
Issue number1
DOIs
StatePublished - May 2009

Keywords

  • Diffusion
  • Diffusion NMR
  • Double PGSE
  • Double-pulsed gradient spin echo
  • Low-q
  • PFG
  • Phantom
  • Pulsed field gradient
  • Spin echo
  • White matter
  • d-PGSE

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