Combination of a multimode antenna and TIAMO for traveling-wave imaging at 9.4 Tesla

Hoffmann, J., Mirkes, C., Shajan, G. , Scheffler, K. and Pohmann, R. (2016) Combination of a multimode antenna and TIAMO for traveling-wave imaging at 9.4 Tesla. Magnetic Resonance in Medicine, 75(1), pp. 452-462. (doi: 10.1002/mrm.25614) (PMID:25732895)

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Purpose: To investigate the performance of a multimode antenna combined with time-interleaved acquisition of modes (TIAMO) for improved 1H image homogeneity as compared to conventional traveling-wave imaging in the human brain at 9.4 Tesla (T). Methods: An adjustable three-port antenna was built to stimulate the propagation of three basic waveguide modes within a 9.4 T scanner bore. For TIAMO, two time-interleaved acquisitions using different linear combinations of these modes were optimized to achieve a homogeneous rooted sum-of-squares combination of their inline image patterns ( inline image). The antenna's transmit and receive performance, as well as local specific absorption rate, were analyzed using experiments and numerical simulations. Results: The optimized TIAMO inline image combination was superior to radiofrequency shimming. Across the entire brain, it improved the homogeneity of the excitation field by a factor of two and its maximum-to-minimum ratio by almost a factor of five as compared to the circularly polarized mode. The two-fold increase in “virtual” receive channels enhanced the parallel imaging performance and enabled the use of higher acceleration factors. Conclusion: Despite the limited number of channels, a remote three-port antenna combined with TIAMO represents an easily implementable setup to achieve void-free 1H images from the entire brain at 9.4 T, which can be used for anatomical localization and B0 shimming.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Gunamony, Dr Shajan
Authors: Hoffmann, J., Mirkes, C., Shajan, G., Scheffler, K., and Pohmann, R.
College/School:College of Medical Veterinary and Life Sciences > School of Psychology & Neuroscience
Journal Name:Magnetic Resonance in Medicine
ISSN (Online):1522-2594
Published Online:02 March 2015

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