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7T head volume coils: Improvements for rostral brain imaging
Author(s) -
Avdievich Nikolai I.,
Hetherington Hoby P.,
Kuznetsov Andrey M.,
Pan Jullie W.
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21660
Subject(s) - electromagnetic coil , head (geology) , radiofrequency coil , homogeneity (statistics) , nuclear magnetic resonance , materials science , human head , volume (thermodynamics) , search coil , magnetic field , biomedical engineering , acoustics , physics , computer science , geology , medicine , magnetic flux , quantum mechanics , geomorphology , machine learning , absorption (acoustics)
Purpose To improve the performance of 7T head coils over the rostral head regions. Due to radiofrequency (RF) field/tissue interactions, the RF magnetic field profile produced by 7T volume head coils is very inhomogeneous, with enhanced sensitivity near the center of the human brain and substantially reduced in the periphery. Materials and Methods Two head‐sized quadrature volume coils of similar diameters but substantially different lengths (17 and 10 cm) were constructed and tested using a 7T Varian Inova system. Results Experimental data demonstrated that by using a shorter volume head‐sized coil or simply by partially moving a head out of the coil, coil efficiency near the top of a head can be improved by 20%. The homogeneity also improved, largely resulting from an increase in peripheral B 1 values. This resulted in 10%–20% variation in axial slices located near the top of a head. Conclusion We have demonstrated a less deeply positioned head or substantially shorter volume coil can significantly improve coil performance and homogeneity for the rostral head at ultrahigh magnetic fields (7T and above). For studies that target superior brain regions, this coil arrangement can be highly effective. J. Magn. Reson. Imaging 2009;29:461–465. © 2009 Wiley‐Liss, Inc.