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“One‐shot” velocity microscopy: NMR imaging of motion using a single phase‐encoding step
Author(s) -
Xia Yang,
Callaghan Paul T.
Publication year - 1992
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.1910230115
Subject(s) - pulse sequence , resolution (logic) , spins , spin echo , microscope , diffusion , chemistry , nuclear magnetic resonance , phase (matter) , physics , materials science , optics , analytical chemistry (journal) , computer science , magnetic resonance imaging , medicine , organic chemistry , chromatography , artificial intelligence , radiology , condensed matter physics , thermodynamics
The use of the pulsed gradient spin‐echo sequence in NMR microscopy enables the measurement of molecular translational motion and simultaneous construction of velocity and self‐diffusion images, a technique that has been termed dynamic NMR microscopy. In this method the PGSE contrast gradient is stepped in a fourth dimension ( q space) and so is inherently inefficient. Provided that one is prepared to sacrifice some of the additional information provided by the multiple PGSE gradient approach, it is possible to construct a velocity image alone by means of a single PGSE phase‐encoding step. We illustrate applications of this method in which a signal from the stationary spins is nulled by the use of both gradient phase cycling and a final “z‐storage” rf pulse. The limits to velocity resolution are around 10μm s −1 in free water but can be considerably smaller for molecules with a low self‐diffusion coefficient. We demonstrate this method in a study of water capillary flow at 12 μm transverse pixel resolution, extending the velocity range by employing a four‐quadrant analysis method. This method is also used to measure vascular transport in a living plant and find a flow rate of around 45μm s −1 . © 1992 Academic Press, Inc.