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Elimination of signal strength dependency upon coil loading–an aid to metabolite quantitation when the sample volume changes
Author(s) -
Hoult David I.,
Deslauriers Roxanne
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.1910160308
Subject(s) - signal (programming language) , nuclear magnetic resonance , electromagnetic coil , sample (material) , chemistry , electrical impedance , materials science , acoustics , analytical chemistry (journal) , physics , chromatography , computer science , quantum mechanics , programming language
The phase, height, and width of NMR spectral lines from a constant number of nuclei are frequently dependent upon changes in probe Q factor and tuning, caused by motion of the sample and/or changes in its electrical conductivity and size. Thus quantitation of metabolites in biological samples can be difficult. When probe tuning and matching are rendered independent by the use of a tuned coupling coil for matching, use of a very low input impedance preamplifier can virtually eliminate such dependencies in the received signal. Likewise, by reciprocity, the use of a low output impedance transmitter greatly reduces the dependence of pulse flip angle upon sample characteristics. Experimental results verifying these statements are presented, and the time course of signals from a swelling, perfused pig heart and an external reference are plotted. © 1990 Academic Press, Inc.