Digital Filter Banks in MR Measurement of Gradient Magnetic Fields

. The sensitivity of spectroscopic methods based on nuclear magnetic resonance (MR) is limited, in particular by the magnitude of noise in the signal being measured. In MR tomography and, above all, in localized spectroscopy and spectroscopic MR imaging, this problem becomes even more pronounced. Wh...

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Bibliographic Details
Published in:Applied magnetic resonance 2008-05, Vol.33 (4), p.399, Article 399
Main Authors: Gescheidtova, E., Kubasek, R., Smekal, Z., Bartusek, K.
Format: Article
Language:English
Subjects:
Adaptive filters
Atoms and Molecules in Strong Fields
Biological properties
Digital filters
Distortion
Eddy currents
Filter banks
Laser Matter Interaction
Line spectra
Magnetic fields
Magnetic resonance imaging
NMR
Nuclear magnetic resonance
Organic Chemistry
Physical Chemistry
Physics
Physics and Astronomy
Signal to noise ratio
Solid State Physics
Spectroscopy/Spectrometry
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Summary:. The sensitivity of spectroscopic methods based on nuclear magnetic resonance (MR) is limited, in particular by the magnitude of noise in the signal being measured. In MR tomography and, above all, in localized spectroscopy and spectroscopic MR imaging, this problem becomes even more pronounced. When gradient magnetic fields are used, it cannot be fully ruled out that there will be a change in the basic magnetic field due to the eddy currents in conducting materials in the neighborhood of the sample being measured. This results in a local change in instantaneous frequency of the resonance of nuclei and in a distortion of spectral lines or MR image. For methods that eliminate this distortion and for an accurate calculation of the constants of (in particular long) preemphasis filters, techniques have been developed and experimentally tested that are based on measuring the instantaneous frequency of the signal detected with a very low signal-to-noise ratio. Adaptive filtering methods and filtering based on filter banks have been developed to reduce the level of noise. Results of these two types of filtering are described in the paper. The filtering techniques developed can be used also in other applications and thus contribute to increasing quality of methods for examining the properties of biological and chemical substances.
ISSN:0937-9347
1613-7507
DOI:10.1007/s00723-008-0084-x