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Please, cite this online document as:
Vasini E.M., Cobas C., and Sykora S.
In-vivo spectra pre-conditioning using PcBc,
Poster at EUROMAR, Nantes, France, July 1-5, 2018,
DOI: 10.3247/SL7Nmr18.002
Abstract
In vivo spectra (1H, 13C, 31P, 23Na, ...) are known to be particularly difficult to phase and to correct for baseline drifts. The reasons are multiple: apart from the usual ones encountered typical of in-vitro spectroscopy, such as post-pulse receiver transfer-function distortions (dead-time), filter delays, filter roll, an a few others, there are additional difficulties due to the following specific factors:
- Low signal-to-noise ratio (S/N),
- Unavoidably bad B1 homogeneity, involving both B1 amplitude and phase.
- Local magnetic field gradients due to mesoscopic susceptibility variations in tissues.
- Broad solid-tissue background signals.
This makes even manual pre-conditioning (phase and baseline corrections) very difficult and subjective.
We present the promising results obtained with a recently developed pre-conditioning method named PcBc which consists in a simultaneous phase and baseline correction using both the in-phase and the out-of-phase parts of a spectrum. The PcBc iterative algorithm is characterized by a quality function related to the amplitude histograms (real and imaginary) of the spectrum.
Since the method is completely automatic, it bears the promise of being also completely objective - a feature which, in our opinion, was so far badly missing in the management of in-vivo NMR spectra.
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