Volumetric imaging with homogenised excitation and static field at 9.4 T

Tse, D. H. Y., Wiggins, C. J., Ivanov, D., Brenner, D., Hoffmann, J., Mirkes, C., Shajan, G., Scheffler, K., Uludağ, K. and Poser, B. A. (2016) Volumetric imaging with homogenised excitation and static field at 9.4 T. Magnetic Resonance Materials in Physics, Biology and Medicine, 29(3), pp. 333-345. (doi:10.1007/s10334-016-0543-6) (PMID:26995492) (PMCID:PMC4891373)

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Abstract

Objectives: To overcome the challenges of B0 and RF excitation inhomogeneity at ultra-high field MRI, a workflow for volumetric B0 and flip-angle homogenisation was implemented on a human 9.4 T scanner. Materials and methods: Imaging was performed with a 9.4 T human MR scanner (Siemens Medical Solutions, Erlangen, Germany) using a 16-channel parallel transmission system. B0- and B1-mapping were done using a dual-echo GRE and transmit phase-encoded DREAM, respectively. B0 shims and a small-tip-angle-approximation kT-points pulse were calculated with an off-line routine and applied to acquire T1- and T 2 * -weighted images with MPRAGE and 3D EPI, respectively. Results: Over six in vivo acquisitions, the B0-distribution in a region-of-interest defined by a brain mask was reduced down to a full-width-half-maximum of 0.10 ± 0.01 ppm (39 ± 2 Hz). Utilising the kT-points pulses, the normalised RMSE of the excitation was decreased from CP-mode’s 30.5 ± 0.9 to 9.2 ± 0.7 % with all B 1 + voids eliminated. The SNR inhomogeneities and contrast variations in the T1- and T 2 * -weighted volumetric images were greatly reduced which led to successful tissue segmentation of the T1-weighted image. Conclusion: A 15-minute B0- and flip-angle homogenisation workflow, including the B0- and B1-map acquisitions, was successfully implemented and enabled us to reduce intensity and contrast variations as well as echo-planar image distortions in 9.4 T images.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Gunamony, Dr Shajan
Authors: Tse, D. H. Y., Wiggins, C. J., Ivanov, D., Brenner, D., Hoffmann, J., Mirkes, C., Shajan, G., Scheffler, K., Uludağ, K., and Poser, B. A.
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Journal Name:Magnetic Resonance Materials in Physics, Biology and Medicine
Publisher:Springer Verlag
ISSN:0968-5243
ISSN (Online):1352-8661
Published Online:19 March 2016
Copyright Holders:Copyright © 2016 The Authors
First Published:First published in Magnetic Resonance Materials in Physics, Biology and Medicine 29(3):333-345
Publisher Policy:Reproduced under a Creative Commons License

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