Pittsburgh Talk

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Functional Magnetic Resonance Imaging and
Intrinsic Optical Imaging Signals Spatial
specificity to neuronally active site
Seong-Gi Kim
Brain Imaging Research Center, University of
Pittsburgh
Supported by NIH, McKnight Fdn, Keck Fdn
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Collaborators
Tim Duong Dae-Shik Kim Noam Harel Fuqiang
Zhao Sang-Pil Lee Ping Wang Tsukasa Nagaoka Eric
Cohen Hiro Fukuda
Costantino Iadecola Kamil Ugurbil Manabu
Tanifuji Bill Eddy
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Functional Brain Mapping ( gta few millimeters)
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Functional Brain Mapping (sub-millimeter)
3x3x3 mm3
Can we resolve cortical laminar and columnar
activity?
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Orientation Columns of Cat Visual Cortex (Area 18)
2-DG map
5 mm
(Lowel Singer, 1990)
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Spatial Specificity

• fMRI Responses
• Perfusion - CBF, CBV
• BOLD (dHb) Conventional gradient-echo and
  spin-echo

• Intrinsic Optical Imaging Signals

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Conventional dHb-based (BOLD) fMRI of Cat Visual
Cortex
Cross Correlation Value
Midline (sagittal sinus)
1 mm
4.7T, GE BOLD
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Vascular structures in the striate cortex
Intracortical veins 80 120 ?m diameter 1 2
mm apart
From Duvernoy, HM. The Human Brain, Surface,
Three-dimensional Sectional Anatomy with MRI, and
Blood Supply. Springer-Verlag, 1999.
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To improve spatial specificity, signals from
large vessels should be minimized.
Is stimulation-induced perfusion response
widespread and diffused?
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Arterial Spin Labeling Perfusion fMRI
1 mm
0.8
CC
0.3
Midline (sagittal sinus)
FAIR w/ Single-Shot EPI 4.7 Tesla
Duong et al. PNAS, 2001
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45o
135o
1 mm
Duong et al. PNAS, 2001
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CBF response is specific to cortical columns. How
about CBV?
Plasma CBV can be measured using MRI after
injection of contrast agent iron oxides.
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Spatial Specificity

• fMRI Responses
• Perfusion - CBF, CBV
• BOLD Conventional gradient-echo and spin-echo

• Intrinsic Optical Imaging Signals

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Orientation Columns obtained dHb-weighted Optical
Imaging
Vessels
1 mm
Columns
620 nm wavelength, differential image
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Spatiodynamics of dHb-weighted optical imaging
signals during single orientation stimulation
Anatomy
-1.0
0.0
0.5
1.0
1.5
2.0
3.0
3.5
4.0
4.5
5.0
5.5
Initial dip high spatial specificity lt- increase
in CMRO2 Later positive change poor spatial
specificity lt- increase in CBF
(Malonek Grinvald, Science, 1996)
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Column-specific dHb signal is relatively small,
regardless of positive or negative signal, when
neural activity-induced dHbs drain into
non-specific large veins. Only early portion
of the dip (before draining into large vessels)
is specific to a sub-millimeter resolution.
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Cerebral blood flow and volume control _at_
microvessels
Capillary/tissue-specific hemodynamic mapping
techniques can image sub-millimeter columnar and
laminar functional structures.
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Thank You