Abstract #0245
Self-Calibrated Simultaneous Multi-Slice PROPELLER
Ola Norbeck 1 , Magnus Mrtensson 2,3 , Enrico Avventi 3 , Mathias Engstrm 1,3 , and Stefan Skare 1,3
1
Dept. of Neuroradiology, Karolinska
University Hospital, Stockholm, Sweden,
2
EMEA
Research and Collaboration, GE Applied Science
Laboratory, GE Healthcare, Stockholm, Sweden,
3
Dept.
of Clinical Neuroscience, Karolinska Institutet,
Stockholm, Sweden
Simultaneous multi-slice (SMS) MR imaging, sometimes in
combination with regular parallel imaging in the phase
encoding direction, has led to a dramatic speed up of
multi-volume echo-planar imaging (EPI) for fMRI and
diffusion MRI. In multi-volume SMS imaging, the first
volume can be acquired without acceleration and be used
for calibration of the subsequent SMS accelerated
volumes.For clinical MRI, most often only involving one
volume per scan, one needs to make sure that the SMS
calibration does not consume a large fraction of the
total scan time. To keep the SMS calibration time short,
a low resolution 2D GRE scan may be used. In this work,
we have developed SMS RF pulses and applied them to
PROPELLER imaging. As PROPELLER uses a large set of
blade volumes (~10 per minute), we suggest to perform
SMS and regular in-plane GRAPPA calibration on the first
propeller blade volume as a part of the scan. With only
one blade volume being fully sampled in both the phase
encoding direction and the slice direction, and with the
remaining blades fully accelerated without any ACS
lines, the overall scan time could be kept very short
and without needing separate GRE scans. For our
accelerated PROPELLER sequence, GRAPPA and
split-slice-GRAPPA was used for unfolding, and the
GRAPPA kernel was rotated to calculate sets of weights
the other blade volumes. The technique was validated
with our T1-W SE PROPELLER sequence. Our work shows that
PROPELLER scans can be accelerated with SMS in addition
to in-plane acceleration, allowing almost 75 % scan time
reduction.
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