th  - 1988 - 51st ENC Conference

a
b
48
SEMUT SPECTRAL EDITING, CALIBRATION OF RF FIELD STRENGTHS, AND
TOSS AT HIGH SPINNING SPEEDS IN 13C CPIMAS NMR OF SOLIDS
N.C.Nielsen *a, H.Bildsee a, H.J.Jakobsen a, and O.W. Ssrensen b
Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark
Laboratorium fur Physikalische Chemie, ETH, CH-8092 Zurich, Switzerland
Pulse techniques for spectral editing have become popular tools for assign-
ment of liquid state 13C NMR spectra. This work describes ~xtension of the con-
cept of spectral editing to include 1D and 2D SEMUT editing of 13C CP/MAS NMR
spectra for solids. Furthermore, as solid state NMR multipulse experiments are
extremely sensitive to missetting of pulse timings we also report a 2D CP/MAS
pulse sequence for fast and accurate calibration of rf field strengths. The se-
quences are based on principles known from ID and 2D NMR experiments of liquids
combined with techniques for obtaining high-resolution NMR spectra of solids.
Finally, we present new and improved four and six ~-pulse TOSS sequences for ef-
ficient suppression of spinning sidebands under various experimental condi-
tions. Compared to earlier sequences the new TOSS schemes are advantageous for
high-speed MAS experiments, for samples with short T2's, or for efficient dipo-
lar dephasing of protonated carbons in 13C CP/MAS NMR at high speeds. Experimen-
tal results obtained using our new sequences will be presented.
49 * I CHEMICAL SHIFT IMAGING OF HUMAN INTERNAL ORGANS AT 1.5T
William J. Thoma , June S. Taylor, Sarah J. Nelson and Truman R. Brown.
Fox Chase Cancer Center, Philadelphia, PA 19111
For NMR spectroscopy to be clinically useful, the sensitivity, quantification and
volume localization must be optimized. Sensitivity is a function of field strength,
homogeneity and rf coll design, quantification can be a~hieved by post-acquisitlon
processing. We have implemented chemical shift imaging (CSI) on a 1.5T Siemens
Magnetom (clinical imager) to localize volumes of interest. The simplest method of
localization is to combine a I-D version of CSI with a surface coll to achieve 3-D
localization. Localized signal is obtained by spin excitation by a non-selectlve rf
pulse from the surface coil followed by an incremented phase-encodlng gradient pulse of
3.1 msec duration. The ADC is turned on immediately after the rf pulse; data obtained
during the gradient-on time is zeroed before fourier transformation. The technique has
been used to obtain heart and liver spectra (Figure la, b, respectively) in 8 min. The
spectra were obtained with a i0 cm, 2 turn surface coll and were from 1.5 and 1.0 cm
thick slices, respectively. The repetition time was i sec with the pulse amplitude
adjusted to produce a nominal 90 ° pulse in the region of interest. 3-D CSI sequences
~ve also been implemented.
T.R. Brown, B.M. Kincaid and K. Ugurbil. PNAS 79, 3523 (1982).
Figure i.
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