th  - 1988 - 51st ENC Conference

- - QUANTIFICATION OF BLOOD FLoW AND TISSUE PERFUSION VIA DEUTERIUM
13 I NMR-THE NOVEL USE OF D20 AS A FREELY DIFFUSIBLE TRACER:
Joseph J.H. Ackerman 1" , Seong-Gi Kim I , Coleen S. Ewy I , Nancy N.
5ecker I , Yuying C. Hwang I , and Robert A. Shalwitz2; Departments of Chemistry I and
Pediatrics 2, Washington University, St. Louis, MO 631301 and 631102 .
NMR has proven to be a valuable technique with which to monitor metabolic events
nondestructively in intact biological systems. The past decade has witnessed dramatic
advances in the development of such spectroscopic analyses employing 31p, 13C, and *H
nuclides. Our laboratory has recently introduced a new approach, employing deuterium
NMR in concert with D20 as a freely diffusible aqueous tracer, for the measurement of
blood flow and tissue perfusion 1'2 This method borrows heavily from multicompart-
ment kinetic modeling used with diffusible radiotracers such as H2150 and 133Xe but,of
course, does not require the special handling procedures associated with radioactive
labels. In addition, the deuterium NMR blood flow determination can be carried out
concomitant with NMR metabolic analysis, thus, correlating in one measurement impaired
substrate delivery and its physiologic consequences. In brief, the tissue or organ in
which blood flow is to be determined is labeled with D20 via either intravenous, intra-
arterial or intratissue bolus injection. Ongoing capillary blood flow, diffusion and
proton-deuteron exchange serve to distribute HOD throughout the tissue's aqueous space.
Further blood flow (unlabeled) then washes out the deuterium residue. The residue
decay (washout) curve is accurately defined via external monitoring, i.e., 2H NMR.
Single*, 2 and multicompartment modeling 3'4 and knowledge of the blood:tissue
partition coefffcient (readily determined independently of the NMR residue decay curve~
allows derivation of blood flow and perfusion in units of ml-blood/(100 g-tissue,min).
The extension of this method to NMR flow-imaging appears feasible s . [References: (i)
J.J.H. Ackerman et al., Proc. Natl. Acad. Sci. USA, 84, 4099 (1987); (2) J.J.H.
Ackerman e~ al., N.Y. Acad. Sci., 508, 89 (1987); (3) S.-G. Kim et al., Cancer
Research, accepted (1987); (4) S.-G. Kim, et al., Magn. Reson. Med., submitted
(1987); (5) C.S. Ewy eC al., Magn. Reson. Med., submitted (1987).]
14 ] SILICON-29 MASNMR ANALYSIS OF SINTERED Si3N 4 CERAMICS:
K. R. Carduner, Ford Motor Company, Dearborn, Michigan, 48121
Silicon nitride is finding application in the transportation industry in
various engine components such as valves, valve seats, or wrist pins that
will operate with less wear and improved thermal characteristics compared
to metal components. Gas turbine rotors constructed from Si3N 4 ceramic
can operate at higher speeds and temperatures without the deformation or
fatigue observed in turbines manufactured from high temperature alloys.
Si3N 4 ceramics are made by conversion at high temperature of ~-Si3N 4
precursor powder packed into a mold to ~-Si3N 4 into which is mixed
approximately 5% of a "sintering aid" such as Y203 . The precursor powder
must be mostly a-Si3N 4 and/or amorphous Si3N 4 phases and low in SiO 2 or
Si2N20 for effective microstructure development during sintering. An NMR
technique to analyze for phase purity in precursor powders has recently
appeared (K. R. Carduner, e t al, Anal. Chem. 59, 2794, 1987). Presently,
it is shown that NMR can provide insight into sintered ceramic as well.
Test ceramics, which are not readily pulverizable, were machined into
cylinders and inserted into alumina MAS rotors. 29Si MASNMR spectra can
distinguish between the ~ and any residual ~-Si3N 4 phase, and it has also
been possible to detect, assign resonances of, and quantify the grain
boundary phases that result from reaction of yttria and Si3N 4. The grain
boundary phases, which are at the level of i to 2 wt%, are often respon-
sible for limiting the high temperature strength of Si3N 4 ceramics.
Quantification of the grain boundary phases by other techniques are
compared with the NMR results. NMR shows strong promise as a method to
study crystalline versus amorphous morphology of the grain boundary
pha~=s.
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