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Effects of velocity profile of to‐and‐fro pulsatile flow on magnetic resonance signal intensity
Author(s) -
Fujita N.,
Harada K.,
Murakami T.,
Akai Y.,
Kozuka T.
Publication year - 1990
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.1910150210
Subject(s) - pulsatile flow , mechanics , flow (mathematics) , flow velocity , signal (programming language) , boundary layer , nuclear magnetic resonance , dispersion (optics) , physics , mean flow , chemistry , optics , turbulence , medicine , computer science , cardiology , programming language
The effects of to‐and‐fro pulsatile flow, i.e., an oscillatory fluid motion with no net flow, on signal intensity in gated spin‐echo magnetic resonance imaging are considered both theoretically and experimentally. On the basis of hydrodynamic principles, to‐and‐fro pulsatile flow at large Womersley numbers consists of uniform inner flow and boundary‐layer‐type flow adjacent to a tube wall. Therefore, the velocity profile is “trapezoidal” rather than parabolic at all times during the pulsation period. Contrary to the absence of phase dispersion and loss of signal within the inner flow where no velocity gradient exists, large velocity differences cause phase dispersion and, hence, loss of signal within the boundary layer, whose thickness is inversely proportional to the Womersley number. An understanding of these features of to‐and‐fro pulsatile flow provides the theoretical basis of cerebrospinal fluid flow phenomena in magnetic resonance imaging, since this type of flow exists in cerebrospinal fluid pathways. © 1990 Academic Press, Inc.