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MR spectroscopy using multi‐ring surface coils
Author(s) -
King Scott B.,
Ryner Lawrence N.,
Tomanek Boguslaw,
Sharp Jonathan C.,
Smith Ian C.P.
Publication year - 1999
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/(sici)1522-2594(199910)42:4<655::aid-mrm6>3.0.co;2-d
Subject(s) - electromagnetic coil , homogeneity (statistics) , spectroscopy , nuclear magnetic resonance , voxel , radiofrequency coil , volume (thermodynamics) , materials science , optics , physics , computer science , quantum mechanics , artificial intelligence , machine learning
A spatially uniform B 1 ‐field is preferred for MR imaging and spectroscopy. Unfortunately, volume coils are sometimes unavailable, or do not provide adequate RF power or SNR for some applications. In quantitative MRS, mean metabolite concentration cannot be evaluated when the coil response is nonuniform, unless an assumption is made concerning the metabolite spatial distribution. It is well known that standard single‐loop surface coils, although offering high SNR characteristics, have poor B 1 homogeneity. New multi‐ring surface coils are proposed which produce a locally uniform B 1 field, with sensitivity and power requirements comparable to those of standard surface coils. MR spectroscopy using two and three‐ring versions of this “local volume coil” result in spatial localization essentially identical to that obtained with a volume coil but with much improved RF power and SNR characteristics. When compared to standard surface coils, the multi‐ring coil offers much improved water suppression and localization, as well as reduced outer voxel contamination, with only a small loss in SNR and moderate increase in SAR. In summary, the multi‐ring coil operates midway between the volume coil and the standard surface coil, retaining the most advantageous properties of both. Magn Reson Med 42:655–664, 1999. Published 1999 Wiley‐Liss, Inc.