th  - 1988 - 51st ENC Conference

170 ]
FLOW-COMPENSATED NMR IMAGING TECHNIQUES FOR RHEOLOGY OF
SUSPENSIONS
P.D. Majors, S.A. Altobelli, E. Fukushima, Lovelace Medical Foundation, Albuquerque, N.M.
87108., and R.C. Givler, Sandia National Laboratories, Albuquerque, N.M. 87185.
A suspension is a mixture of solid particles in a viscous fluid. Many natural processes (e.g.,
blood circulation and river sedimentation) and industrial processes (e.g., transport of slurries and
filtration) are affected by the properties of suspensions. Unforttmately, there is a dearth of rhe-
ological information for suspensions at ILigh concentrations due to limitations suffered by most
measurement teclmiques. NMR yields spatially resolved quantitative velocity mid particle density
information.
We used flow-compensating NMR imaging techniques to determine the flow properties (fluid
and particle velocity distributious, particle density distribution) of viscous suspensions. Constituent
concentrations for flowing two-phase systems can be obtained by time-averaging the resonant signal
of, say, the fluid phase. The concentration of the second phase is thus inferred from the 'reduced'
fluid signal. Preliminary NMR studies of two-phase stationary and flowing systems demonstrate
the quantitative nature of the tecludques with good sensitivity and resolution.
RAPID ROTATING FRAME IMAGING WITH RETENTION OF CHEMICAL SHIFT
INFOP~MATION .~ M #*
171 J P.M. Macdonald ~, K.R. etz , J.P. Boehmer +
#Radiology Department, New England Deaconess Hospital, Harvard Medical School, 185
Pilgrim Road, Boston, MA 02215
+Department of Internal Medicine, University of Massachusetts Medical Center, 55 Lake
Avenue North, Worcester, MA 01605
Rotating frame imaging (RFI) is an elegant and simple technique for mapping the
spatial distribution of NMR spectral information (I). The image is formed by using a
homogeneous static field B and an rf field gradient B.(x) generated with a surface
coil. Spins in different s~atial regions exhibit nutatlon frequencies u I which are
proportional to the rf field strength: Ul=YBl(X)/2~. In Rapid RFI, whic~ is several
orders of magnitude faster than conventional RFI, the spectral line of interest is
)laced on-resonance and a single FID of n points is acquired (2) using:
Preparation - (Pulse - Acquire One Point) - Relaxation.
[DFT then produces an image relating spin density and nutati~nal frequency (spatial
distribution). Unfortunately, spatial information from off-resonance signals remains
intermixed.
Our approaches to removing the undesired signals include: a) selective +90 vs -90 °
tipping of the signal of interest using DANTE such that the difference image contains
only the desired information, b) P~I with and without selective inversion using shaped
pulses (3) in order to eliminate extraneous signals using subtraction, and c) removal
of off-resonance contributions by virtue of their fast decay in the Rapid RFI sequence.
(I) D.Hoult, J.Magn.Reson. 33, 183 (1979).
(2) K.Metz and J. Boehmer, J.Magn. Reson., submitted.
(3) M.Silver, R.Joseph, and D.Hoult, J.Magn.Reson. 59, 347 (1984).
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