TY - JOUR
T1 - Measuring small compartmental dimensions with low-q angular double-PGSE NMR
T2 - The effect of experimental parameters on signal decay
AU - Shemesh, Noam
AU - Özarslan, Evren
AU - Basser, Peter J.
AU - Cohen, Yoram
N1 - Funding Information:
P.J.B and E.O were supported by the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development.
PY - 2009/5
Y1 - 2009/5
N2 - 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.
AB - 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.
KW - Diffusion
KW - Diffusion NMR
KW - Double PGSE
KW - Double-pulsed gradient spin echo
KW - Low-q
KW - PFG
KW - Phantom
KW - Pulsed field gradient
KW - Spin echo
KW - White matter
KW - d-PGSE
UR - http://www.scopus.com/inward/record.url?scp=63349083917&partnerID=8YFLogxK
U2 - 10.1016/j.jmr.2009.01.004
DO - 10.1016/j.jmr.2009.01.004
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AN - SCOPUS:63349083917
SN - 1090-7807
VL - 198
SP - 15
EP - 23
JO - Journal of Magnetic Resonance
JF - Journal of Magnetic Resonance
IS - 1
ER -