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Sensitivity calculations and comparisons for shielded elliptical and circular birdcage coils
Author(s) -
De Zanche Nicola,
Allen Peter S.
Publication year - 2002
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.10039
Subject(s) - shielded cable , electromagnetic coil , physics , shield , radiofrequency coil , sensitivity (control systems) , electromagnetic shielding , optics , quadrature (astronomy) , acoustics , nuclear magnetic resonance , computational physics , computer science , electronic engineering , telecommunications , engineering , petrology , quantum mechanics , geology
An analytical framework is presented which justifies the use of a confocal elliptical shield (previously adopted on empirical or numerical grounds) to limit the spatial extent of the radiofrequency (RF) field produced by an elliptical birdcage coil, while concurrently minimizing field inhomogeneities. From this analytical capability it is further shown that the relative linear mode geometric sensitivities depend only on the shield dimensions and can be readily evaluated, thus providing an upper bound to the improvement in signal‐to‐noise ratio (SNR) of the damped elliptical birdcage over a circular coil of similar dimensions. The mismatch in the linear mode sensitivities can also be evaluated, and a method for the design of an appropriate feed configuration that ensures quadrature operation is given. Magn Reson Med 47:364–371, 2002. © 2002 Wiley‐Liss, Inc.