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Multi‐Turn Transmit Coil to Increase B 1 Efficiency in Current Source Amplification
Author(s) -
Gudino N.,
Griswold M. A.
Publication year - 2013
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.24612
Subject(s) - electromagnetic coil , amplifier , current (fluid) , transistor , coil noise , electrical engineering , current source , power (physics) , dissipation , materials science , cmos , optoelectronics , rogowski coil , voltage , physics , engineering , thermodynamics , quantum mechanics
Purpose A multi‐turn transmit surface coil design was presented to improve B 1 efficiency when used with current source amplification. Methods Three different coil designs driven by an on‐coil current‐mode class‐D amplifier with current envelope feedback were tested on the benchtop and through imaging in a 1.5 T scanner. Case temperature of the power field‐effect transistor at the amplifier output stage was measured to evaluate heat dissipation for the different current levels and coil configurations. In addition, a lower power rated device was tested to exploit the potential gain in B 1 obtained with the multi‐turn coil. Results As shown both on the benchtop and in a 1.5 T scanner, B 1 was increased by almost 3‐fold without increasing heat dissipation on the power device at the amplifier's output using a multi‐turn surface coil. Similar gain was obtained when connecting a lower power rated field‐effect transistor to the multi‐turn coil. Conclusion In addition to reduce heat dissipation per B 1 in the device, higher B 1 per current efficiency allows the use of field‐effect transistors with lower current ratings and lower port capacitances, which could improve the overall performance of the on‐coil current source transmit system. Magn Reson Med 69:1180–1185, 2013. © 2013 Wiley Periodicals, Inc.