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Online motion correction for diffusion-weighted segmented-EPI and FLASH imaging

MPS-Authors
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Weih,  Katrin S.
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Driesel,  Wolfgang
Methods and Development Unit Nuclear Magnetic Resonance, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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von Mengershausen,  Michael
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Norris,  David G.
Department Cognitive Neurology, MPI for Human Cognitive and Brain Sciences, Max Planck Society;

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Citation

Weih, K. S., Driesel, W., von Mengershausen, M., & Norris, D. G. (2004). Online motion correction for diffusion-weighted segmented-EPI and FLASH imaging. Magnetic Resonance Materials in Physics, Biology and Medicine, 16(6), 277-283. doi:10.1007/s10334-004-0036-x.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0010-CE00-E
Abstract
This paper explores the application of online motion correction using navigator echoes to the segmented-EPI and FLASH techniques. In segmented EPI this has the advantage over post-acquisition correction that the position in k-space of each segment is no longer subject to arbitrary shifts caused by rotation. In diffusion-weighted FLASH it has the advantage that the full magnetisation can be utilised in comparison to other methods of eliminating the sensitivity to bulk motion, in which the sensitivity is halved. Healthy subjects were investigated on a 3 T whole-body system in which the hardware has been modified so that navigator echoes can be recorded on a personal computer which generates the necessary magnetic field gradient correction pulses and shifts in the Larmor frequency within 800 μs. ECG triggering was used to avoid the period of non-rigid-body brain motion. Two orthogonal navigator echoes were employed. For segmented EPI it was found essential to minimise the T2* weighting of the navigator echoes to about 10 ms to obtain reliable results. High quality images were obtained for both methods examined. Online motion correction brings direct benefits to both the diffusion-weighted segmented-EPI and FLASH techniques.