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Understanding and manipulating the RF fields at high field MRI
Author(s) -
Ibrahim Tamer S.,
Hue YikKiong,
Tang Lin
Publication year - 2009
Publication title -
nmr in biomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.278
H-Index - 114
eISSN - 1099-1492
pISSN - 0952-3480
DOI - 10.1002/nbm.1406
Subject(s) - electromagnetics , electromagnetic field , imaging phantom , field (mathematics) , excitation , computational electromagnetics , radio frequency , physics , electromagnetism , magnetic field , power (physics) , computational physics , specific absorption rate , computer science , acoustics , electronic engineering , electrical engineering , engineering , optics , mathematics , quantum mechanics , antenna (radio) , pure mathematics
This paper presents a complete overview of the electromagnetics (radiofrequency aspect) of MRI at low and high fields. Using analytical formulations, numerical modeling (computational electromagnetics), and ultrahigh field imaging experiments, the physics that impacts the electromagnetic quantities associated with MRI, namely (1) the transmit field, (2) receive field, and (3) total electromagnetic power absorption, is analyzed. The physical interpretation of the above‐mentioned quantities is investigated by electromagnetic theory, to understand ‘What happens, in terms of electromagnetics, when operating at different static field strengths?’ Using experimental studies and numerical simulations, this paper also examines the physical and technological feasibilities by which all or any of these specified electromagnetic quantities can be manipulated through techniques such as B 1 shimming (phased array excitation) and signal combination using a receive array in order to advance MRI at high field strengths. Pertinent to this subject and with highly coupled coils operating at 7 T, this paper also presents the first phantom work on B 1 shimming without B 1 measurements. Copyright © 2009 John Wiley & Sons, Ltd.