Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-56439
Brunner, D O; Paška, J; Froehlich, J; Pruessmann, K P (2011). Traveling-wave RF shimming and parallel MRI. Magnetic Resonance in Medicine, 66(1):290-300.
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At sufficiently high Larmor frequencies, traveling electromagnetic waves along a magnet bore can be used for remote magnetic resonance excitation and detection, effectively using the bore as a waveguide. So far, this approach has relied only on the lowest waveguide modes and thus has not supported multiple-channel operation for radiofrequency shimming and parallel imaging. In this work, this limitation is addressed by establishing a larger number of propagating modes and tapping their spatial field diversity with multiple waveguide ports. The number of available modes is increased by loading with dielectric inserts; the ports are implemented by stub and loop couplers at the end of a waveguide extension. The resulting traveling-wave array, operated at 298 MHz in a 7T whole-body magnet, is shown to enable radiofrequency shimming as well as parallel imaging with commonly used acceleration factors. The last part of the study concerns the amount of dielectric loading that is required. For the given Larmor frequency and bore dimensions, it is found that rather few water-filled inserts, occupying ∼5% of the bore cross-section, are sufficient for effective parallel imaging.
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|Item Type:||Journal Article, refereed, original work|
|Communities & Collections:||04 Faculty of Medicine > Institute of Biomedical Engineering|
610 Medicine & health
|Deposited On:||22 Jan 2012 20:20|
|Last Modified:||16 Jan 2014 02:37|
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