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A new method for flow velocity measurement: Frequency encoded NMR
Author(s) -
Caprihan A.,
Davis J. G.,
Altobelli S. A.,
Fukushima Eiichi
Publication year - 1986
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.1910030223
Subject(s) - pulsatile flow , pulse sequence , nuclear magnetic resonance , flow velocity , pulse (music) , flow (mathematics) , distribution (mathematics) , vector field , fourier transform , echo (communications protocol) , mechanics , physics , chemistry , mathematics , mathematical analysis , optics , computer science , computer network , detector , cardiology , medicine
We demonstrate a new rapid NMR method to measure the average velocity and the velocity distribution of a flowing fluid. We use a truncated Carr‐Purcel‐Meiboom‐Gill pulse sequence, π/2‐ T ‐π‐2 T ‐π‐ T ‐echo, in the presence of a static magnetic field gradient. The π/2 pulse is selective and tags a narrow slice of nuclei. The second echo from the tagged nuclei is Fourier transformed after the nuclei have evolved for a time 4 T to give the velocity distribution modified by the initial slice selection profile. In this way, average velocities up to 54 cm/s were measured for water flowing in a plastic tube with either a plug or a developed velocity distribution. Each measurement required about 20 ms but this could be reduced with larger field gradients. Thus, this method is fast enough to apply to such problems as measuring pulsatile flow in arteries. © 1986 Academic Press, Inc.