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Noise correlation
Author(s) -
Jesmanowicz A.,
Hyde James S.,
Froncisz W.,
Kneeland J. Bruce
Publication year - 1991
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.1910200105
Subject(s) - inductance , electromagnetic coil , physics , decoupling (probability) , noise (video) , signal (programming language) , antiparallel (mathematics) , acoustics , nuclear magnetic resonance , topology (electrical circuits) , mathematics , computer science , magnetic field , quantum mechanics , engineering , artificial intelligence , combinatorics , control engineering , voltage , image (mathematics) , programming language
Calculations and experiments that provide support for our previously stated theorem are presented: If two coils simultaneously receiving magnetic resonance signals from the same anatomic region exhibit zero mutual inductance, there can be no correlation of the noise. It is shown that correlation does not exist even in the presence of mutual inductance unless the two signal paths have amplifiers prior to signal combination. It is further found that in the presence of mutual inductance with ideal amplifiers (0 dB noise figure) in the two signal paths, there is no correlation of noise. In order to satisfy the condition of zero mutual inductance, it may be necessary to employ a decoupling circuit external to the body. A novel coil assembly, which was used in the experiments, places a single‐turn surface coil in the median plane between the two loops of a counter rotating current coil. The signal‐to‐noise ratio can be improved by combining signals. This is in analogy to quadrature receiving coils, where the mutual inductance is zero because vector reception fields are perpendicular. In the present geometry, vector reception fields are collinear, but are parallel and antiparallel on the two sides of the coil assembly, resulting in zero mutual inductance. © 1991 Academic Press, Inc.