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Microstrip RF surface coil design for extremely high‐field MRI and spectroscopy
Author(s) -
Zhang Xiaoliang,
Ugurbil Kamil,
Chen Wei
Publication year - 2001
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.1212
Subject(s) - electromagnetic coil , microstrip , materials science , electromagnetic shielding , radiofrequency coil , conductor , ground plane , nuclear magnetic resonance , imaging phantom , optics , dielectric , acoustics , optoelectronics , electrical engineering , physics , composite material , antenna (radio) , engineering
A new type of high‐frequency RF surface coil was developed for in vivo proton or other nuclei NMR applications at 7T. This is a purely distributed‐element and transmission line design. The coil consists of a thin strip conductor (copper or silver) and a ground plane separated by a low‐loss dielectric material with a thickness ( H ). Due to its specific semi‐open transmission line structure, substantial electromagnetic energy is stored in the dielectric material between the thin conductor and the ground plane, which results in a reduced radiation loss and a reduced perturbation of sample loading to the RF coil compared to conventional surface coils. The coil is characterized by a high Q factor, no RF shielding, small physical coil size, lower cost, and easy fabrication. A brief theoretical description of the microstrip RF coil is given that can be used to guide the coil designs. A set of gradient‐recalled echo images were acquired by using the single‐ and two‐turn microstrip RF surface coils from both phantom and human brain at 7T, which show good penetration and sensitivity. The two‐turn coil design significantly improves the B 1 symmetry as predicted by the microstrip theory. The optimum H for microstrip surface coils is approximately 7 mm. This coil geometry yields a B 1 penetration similar to that of conventional surface coils. SNR comparison was made between the microstrip coil and conventional surface coils with and without RF shielding. The results reveal that the novel surface coil design based on the microstrip concept makes very high‐field MRI/MRS more convenient and efficient in research and future clinics. Magn Reson Med 46:443–450, 2001. © 2001 Wiley‐Liss, Inc.