Premium
Approaching ultimate intrinsic signal‐to‐noise ratio with loop and dipole antennas
Author(s) -
Lattanzi Riccardo,
Wiggins Graham C.,
Zhang Bei,
Duan Qi,
Brown Ryan,
Sodickson Daniel K.
Publication year - 2018
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.26803
Subject(s) - dipole , physics , magnetic dipole , electromagnetic coil , loop (graph theory) , nuclear magnetic resonance , magnetic field , signal to noise ratio (imaging) , electric field , signal (programming language) , computational physics , computer science , optics , mathematics , quantum mechanics , combinatorics , programming language
Purpose Previous work with body‐size objects suggested that loops are optimal MR detectors at low fields, whereas electric dipoles are required to maximize signal‐to‐noise ratio (SNR) at ultrahigh fields ( ≥ 7 T). Here we investigated how many loops and/or dipoles are needed to approach the ultimate intrinsic SNR (UISNR) at various field strengths. Methods We calculated the UISNR inside dielectric cylinders mimicking different anatomical regions. We assessed the performance of various arrays with respect to the UISNR. We validated our results by comparing simulated and experimental coil performance maps. Results Arrays with an increasing number of loops can rapidly approach the UISNR at fields up to 3 T, but are suboptimal at ultrahigh fields for body‐size objects. The opposite is true for dipole arrays. At 7 T and above, 16 dipoles provide considerably larger central SNR than any possible loop array, and minimal g factor penalty for parallel imaging. Conclusions Electric dipoles can be advantageous at ultrahigh fields because they can produce both curl‐free and divergence‐free currents, whereas loops are limited to divergence‐free contributions only. Combining loops and dipoles may be optimal for body imaging at 3 T, whereas arrays of loops or dipoles alone may perform better at lower or higher field strengths, respectively. Magn Reson Med 79:1789–1803, 2018. © 2017 International Society for Magnetic Resonance in Medicine.