| fMRI: Acquisition Methods |
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Monday 20 April 2009 |
| Room 323ABC |
11:00-13:00 |
Moderators: |
Luis Hernandez-Garcia and Hanzhang Lu |
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11:00 |
12. |
Functional MRI Using
Arteriolar Cerebral Blood Volume Changes |
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Jun
Hua1, Qin Qin1, Manus J.
Donahue2, Jinyuan Zhou1, James
J. Pekar1, Peter CM van Zijl1
1Dept. of Radiology, The Johns Hopkins
University, Baltimore, MD, USA;
2Dept. of Clinical Neurology, University
of Oxford, Oxford, UK |
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Vascular
changes during functional brain activity occur
predominantly in the arterioles, and an MRI method
sensitive to such changes is expected to improve
spatial and temporal specificity for fMRI.
Vascular-space-occupancy (VASO) fMRI is a blood-nulling
approach assessing total CBV changes. We introduce
an approach called “inflow VASO” or “iVASO”, which
nulls only blood flowing into the slice. By using a
blood-nulling time comparable to arterial transit
times (~700ms), iVASO signal was sensitized to
predominantly arteriolar blood volume effects. This
arteriolar character was subsequently reflected in
an effectively immediate hemodynamic response for
iVASO when studying visual activation. |
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11:12 |
13. |
Neuronal
Activity-Induced Cerebral Blood Volume Changes in
Humans: Measurements with VASO and VERVE |
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Claire
Cohalan1, Jean J. Chen1, G.
Bruce Pike1
1McConnell Brain Imaging Center, Montréal
Neurological Institute, McGill University, Montréal,
Québec, Canada |
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The
vascular-space-occupancy (VASO) technique targets
changes in total cerebral blood volume (CBV),
whereas the venous-refocusing for volume-estimation
(VERVE) technique measures changes in venous CBV,
which is more relevant for BOLD. In this work, ΔCBV
measurements acquired in healthy humans using both
techniques were compared. VASO produced a higher
contrast-to-noise ratio and larger ΔCBV values than
VERVE, as expected since VERVE measures only venous
CBV changes. VERVE-based activation was more
correlated with BOLD activation, since BOLD is
sensitive to the venous compartment. Though the VASO
technique is easier to implement, its signal
potentially has many contributions other than CBV,
and eliminating these contaminants is difficult, but
necessary. |
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11:24 |
14. |
Whole-Brain Non-Invasive Hemodynamic Imaging,
Enabled by a Novel CBV-Weighted Single-Shot 3D VASO-FLAIR
GRASE Sequence Combined with CBF-Weighted ASL and
BOLD FMRI, Identifies Regional Hemodynamic and
Metabolic Discrepancies |
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Manus J.
Donahue1, Jakob U. Blicher2,
Bradley J. MacIntosh1, Karla L. Miller1,
Leif Ostergaard2, David A. Feinberg3,4,
Matthias Guenther3, Peter Jezzard1
1Clinical Neurology, The University of
Oxford, Oxford, UK; 2Center for
Functionally Integrative Neuroscience, Arhus
University Hospital, Arhus, Denmark; 3Advanced
MRI Technologies, Sebastopol, CA, USA; 4University
of California at Berkeley, Berkeley, CA, USA |
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VASO-FLAIR
magnetization preparation, previously limited to
single-slice imaging, is appended to a single-shot
3D-GRASE readout to generate whole-brain CBV-weighted
maps. CBV-weighted courses are compared to BOLD and
CBF-weighted ASL during and following motor and
visual stimulation. The 3D-GRASE VASO-FLAIR approach
gives similar CBV traces to those found from
single-slice techniques and corresponds well with
BOLD and ASL. Following stimulation, the BOLD
post-stimulus undershoot is larger and endures
longer in visual cortex compared to motor cortex,
whereas CBV and CBF returns to baseline at the same
time. |
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11:36 |
15. |
3D
Single-Shot VASO FMRI Using a Maxwell-Gradient
Compensated GRASE Sequence |
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Benedikt
Andreas Poser1,2, David G. Norris1,2
1Erwin L. Hahn Institute for Magnetic
Resonance Imaging, University Duisburg-Essen, Essen,
Germany; 2Donders Institute for Brain,
Cognition and Behaviour, Radboud University Nijmegen,
Nijmegen, Netherlands |
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The VASO
sequence was recently proposed as first fMRI method
capable of detecting activation related CBV changes
without the need for a contrast agent. We here
present a new whole-brain VASO technique based on a
parallel-accelerated single-shot 3D GRASE sequence.
A flow-compensated correction scheme for concomitant
Maxwell gradients is introduced, and shown to be an
essential feature for 3D GRASE sequences at 3T if
smearing artifacts due to violation of the CPMG
condition in off-resonance excitation are to be
avoided. The effectiveness of the new method
demonstrated in fMRI studies with visuo-motor
stimulation, and a cognitive Stroop task paradigm. |
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11:48 |
16. |
Studies
of BOLD Signal Characteristics Using a Modified
HASTE Sequence with GRAPPA |
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Yongquan
Ye1, Yan Zhuo1, Rong Xue1,
Dehe Weng1,2, Xiaohong Joe Zhou3
1State Key Laboratory of Brain and
Cognitive Science, Institute of Biophysics, CAS,
Beijing, China; 2Siemens Mindit Magnetic
Resonance Ltd., Shenzhen, China; 3University
of Illinois Medical Center, Chicago, IL, USA |
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Turbo
spin echo (TSE) has been proposed as an alternative
to echo planar imaging (EPI) for fMRI. We have used
a modified HASTE (mHASTE) sequence with GRAPPA to
investigate TSE signal characteristics in fMRI and
compared the results with gradient-echo and
spin-echo EPI. mHASTE exhibited reliable and
consistent activation with higher SNR than EPI and
minimal artifacts. More interestingly, we have
observed evidence suggesting that BOLD signals in
mHASTE can be dominated by extravascular
contributions around microvascular networks, which
offers more accurate localization of neurofunctional
activities. |
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12:00 |
17. |
A
Parallel Transmission Method for Improved BOLD FMRI |
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Weiran
Deng1, Cungeng Yang1,
Vijayanand Alagappan2, Lawrence L. Wald2,
V A. Stenger1
1University of Hawaii JABSOM, Honolulu,
HI, USA; 2Harvard University Martinos
Center for Biomedical Imaging, Charlestown, MA |
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Susceptibility-induced gradients at the air/tissue
interface above the sinus regions create signal
voids in axial slices of the orbitofrontal cortex (OFC)
in BOLD fMRI. We present a parallel transmission
technique to recover signal in the OFC with a
customized four-channel TR array. A slice-selection
pulse with a unique time shift is applied into each
channel. Signal recovery and increased BOLD
activation in the OFC is demonstrated during a
breath-holding task at 3T. |
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12:12 |
18. |
Comparison of Template and Individual-Based Gradient
Compensated EPI in Regions Affected by Local
Susceptibility-Induced Signal Loss |
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Jochen
Rick1, Oliver Speck2, Olaf
Dössel3, Jürgen Hennig1, Maxim
Zaitsev1
1Dept. of Diagnostic Radiology, Medical
Physics, University Hospital Freiburg, Freiburg,
Germany; 2Biomedical Magnetic Resonance,
Otto-von-Guericke University, Magdeburg, Germany;
3Institute of Biomedical Engineering,
University Karlsruhe (TH), Karlsruhe, Germany |
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Anatomy-related susceptibility gradients in the
human head lead to artefacts in echo planar imaging
(EPI). The use of a slice-dependent common gradient
compensation template improves fMRI sensitivity in
areas affected by strong susceptibility gradients.
This study evaluates the concept through a
comparison between four groups (no compensation,
common template (member), common template (not
member), individual). In general the signal
improvement of the three compensated cases is about
35%. No significant variations are present between
these cases. Thus, it seems possible to use this
method for functional experiments without repeating
the calibration individually, thus saving adjustment
and calculation time. |
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12:24 |
19. |
Robust
Detection of Functional Activation in the Superior
Colliculus Without ECG-Triggering
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Ute
Goerke1, Kamil Ugurbil1
1Radiology, CMRR/University of Minnesota
Medical School, Minneapolis, MN, USA |
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In fMRI,
high spatial resolution is usually achieved by
segmenting the echo-planar imaging (EPI) acquisition
scheme. However, such images are susceptible to
ghosting due to pulsatile flow of blood and
cerebrospinal fluid (CSF), especially in regions
near the brain stem. We propose a novel post
processing technique, the spectral side band
analysis (SSBA), to detect activation in deep brain
structures without the need of ECG-triggering. This
is demonstrated in a high resolution fMRI study of
the superior colliculus stimulated with a visual
paradigm. |
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12:36 |
20. |
Simultaneous Monitoring of Tongue Tip Movements in
Functional MRI Motor Tasks for Speech and Swallowing
Studies
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Bradley
P. Sutton1,2, Charles A. Conway1,
David P. Kuehn3
1Bioengineering Department, University of
Illinois at Urbana-Champaign, Urbana, IL, USA;
2Beckman Institute, University of Illinois at
Urbana-Champaign, Urbana, IL, USA; 3Speech
and Hearing Science, University of Illinois at
Urbana-Champaign, Champaign, IL, USA |
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A pulse
sequence is developed that acquires images of
dynamic movement of the tongue during speech or
swallowing simultaneously with the acquisition of
functional MRI data. A single midsagittal dynamic
slice is acquired at 16 frames per second while
several oblique axial functional slices are acquired
with lower temporal resolution and functional MRI
contrast. The acquisition allows for real-time
monitoring of task performance without the need for,
or interference from, additional monitoring
hardware. The sequence is shown to detect similar
activations of the primary motor cortex in a
self-paced compared to a cued tongue-tapping task. |
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12:48 |
21. |
Investigating the Whole Brain with 1.5mm Isotropic
Resolution and 1.5s TRs Using Highly Accelerated
High-Field FMRI |
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Cheryl A.
Olman1,2, Steen Moeller2,
Jennifer F. Schumacher3, Serena K.
Thompson3, Edward J. Auerbach2,
Kamil Ugurbil2, Essa Yacoub2
1Psychology, University of Minnesota,
Minneapolis, MN, USA; 2Radiology,
University of Minnesota, Minneapolis, MN, USA;
3Neuroscience, University of Minnesota,
Minneapolis, MN, USA |
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Neuroscientists who want to take advantage of the
higher spatial resolutions afforded by the increased
SNR and CNR at 7 Tesla do not want to sacrifice
temporal resolution in exchange for whole-brain
coverage with high spatial resolution. A multi-band
acquisition at 7T (simultaneous excitation of 4
coronal slices) permits whole-brain coverage with
higher spatial and temporal resolutions than
previously feasible. In this study we measure
whole-brain activation patterns during a visual
object recognition task with 1.5 mm spatial
resolution and 1.5 s temporal resolution.
Whole-brain, high-resolution fMRI is therefore
possible with temporal resolutions sufficient for
event-related designs. |
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