Premium
Design of a radiative surface coil array element at 7 T: The single‐side adapted dipole antenna
Author(s) -
Raaijmakers A. J. E.,
Ipek O.,
Klomp D. W. J.,
Possanzini C.,
Harvey P. R.,
Lagendijk J. J. W.,
van den Berg C. A. T.
Publication year - 2011
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.22886
Subject(s) - electromagnetic coil , poynting vector , imaging phantom , dipole antenna , acoustics , antenna array , dipole , physics , optics , antenna (radio) , computer science , magnetic field , telecommunications , quantum mechanics
Ultra high field MR imaging (≥7 T) of deeply located targets in the body is facing some radiofrequency‐field related challenges: interference patterns, reduced penetration depth, and higher Specific Absorbtion Ratio (SAR) levels. These can be alleviated by redesigning the elements of the transmit or transceive array. This is because at these high excitation field ( B 1 ) frequencies, conventional array element designs may have become suboptimal. In this work, an alternative design approach is presented, regarding coil array elements as antennas. Following this approach, the Poynting vector of the element should be oriented towards the imaging target region. The single‐side adapted dipole antenna is a novel design that fulfills this requirement. The performance of this design as a transmit coil array element has been characterized by comparison with three other, more conventional designs using finite difference time domain (FDTD) simulations and B + 1measurements on a phantom. Results show that the B + 1level at the deeper regions is higher while maintaining relatively low SAR levels. Also, the B + 1field distribution is more symmetrical and more uniform, promising better image homogeneity. Eight radiative antennas have been combined into a belt‐like surface array for prostate imaging. T 1 ‐weighted (T1W) and T 2 ‐weighted (T2W) volunteer images are presented along with B + 1measurements to demonstrate the improved efficiency. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.