4D Flow Imaging in the Aorta at 7T: Impact of Dynamic RF Shimming and kt-Acceleration
Sebastian Schmitter 1 , Susanne Schnell 2 , Kamil Ugurbil 1 , Michael Markl 2 , and Pierre-Francois van de Moortele 1
Center for Magnetic Resonance Research,
University of Minnesota, Minneapolis, MN, United States,
of Radiology, Northwestern University, Chicago, IL,
There is growing interest in using time-resolved 3D
phase-contrast MRI with three-directional velocity
encoding (4D flow MRI) for the assessment of aortic
hemodynamics. Previous studies investigating
intracranial 3D blood flow have shown that 4D flow MRI
directly benefits from ultra-high fields (i.e.≥7T).
However, at 7T short RF wavelength can result in areas
void of transmit B1 (B1+), especially in the torso,
requiring multi-channel B1+ methods. Here, we
demonstrate successful 4D flow imaging in the entire
thoracic aorta at 7T. Two critical methodological
components are investigated: 1) dynamically applied
multiple B1+ shim settings through the acquisition and
2) kt-Grappa acceleration.
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