๐”– Bobbio Scriptorium
โœฆ   LIBER   โœฆ

A Birdcage Coil Tuned by RF Shielding for Application at 9.4 T

โœ Scribed by Bernard J. Dardzinski; Shizhe Li; Christopher M. Collins; Gerald D. Williams; Michael B. Smith

Publisher
Elsevier Science
Year
1998
Tongue
English
Weight
537 KB
Volume
131
Category
Article
ISSN
1090-7807

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โœฆ Synopsis

The design and performance of an inductively fed low-pass birdcage radiofrequency (RF) coil for applications at 9.4 T are described where tuning is accomplished by mechanically moving a concentric RF shield about the longitudinal axis of an RF coil. Moving the shield about the RF coil effectively changes the mutual inductance of the system, providing a mechanism for adjusting the resonant frequency. RF shield tuning eliminates adjustable capacitors on the legs of the RF coil, eliminates current imbalances and field distortions, and results in improved B1 field homogeneity and high quality (Q) factors. RF shield tuning and inductive matching provide an isolated resonance structure which is both physically and electrically unattached. Experimental analysis of shield position on both B1 field homogeneity and resonant frequency is provided. Computer simulations of B1 field homogeneity as a function of shield position and shield diameter are also presented. Magnetic resonance microimaging substantiates the usefulness of this design.

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