TRADITIONAL POSTER - ismrm

Poster Sessions
weeks) after experimental kindling induced epilepsy. The data indicate that there is considerable neuroplasticity and development of new pathways during
the progression of epilepsy. Whether comparable plasticity of cortical maps is present in humans should be tested using fMRI in future studies, considering
that such seizure-induced changes may be involved in producing interictal behavioural disturbances.
1207. Layer-Specific FMRI of Photic Stimulation in the Rat Retina at 11.7 T
Yen-Yu Ian Shih 1 , Bryan H. De La Garza 1 , William J. Lavery 1 , Eric R. Muir 1,2 , Timothy Q. Duong 1
1 Research Imaging Institute, Ophthalmology/Radiology, University of Texas Health Science Center at San Antonio, San Antonio, TX,
United States; 2 Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
The retina is about 276 micron thick including the choroid and has highly organized laminar structures. This study reports, for the first time, the feasibility of
high-resolution blood-volume fMRI to image layer specific (retinal and choroidal) visual responses in the rat retina at 11.7T up to 40x40x600 micron
nominal resolution. Given that the choroid is behind the retina and the retinal pigment epithelium, it is generally inaccessible by optical techniques. Bloodvolume
fMRI thus could provide a unique means to evaluate lamina-specific functional changes in the rat retina where many retinal disease models are
readily available.
1208. Pass-Band Balanced Steady State Free Precession Functional MRI of the Mouse Retina
Eric Raymond Muir 1,2 , Sung-Hong Park 3 , Timothy Q. Duong 2
1 Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, United States; 2 Research Imaging Institute,
Ophthalmology/Radiology, UT Health Science Center San Antonio, San Antonio, TX, United States; 3 Research Imaging Institute,
Radiology, UT Health Science Center San Antonio, San Antonio, TX, United States
BOLD fMRI of the thin retina with the widely used EPI acquisition is challenging because the eye is a region of large magnetic inhomogeneity and highresolution
EPI is pushing the limits of gradient performance, resulting in susceptibility-induced signal drop out and image distortion. To overcome these
limitations, we implemented a pass-band balanced steady state free precession (bSSFP) sequence for fMRI of the mouse retina at 45x45x500 µm. bSSFP has
comparable temporal resolution and SNR per unit time as EPI, without the artifacts common in EPI. bSSFP fMRI could reliably detect layer-specific
responses to hypoxic challenge in the mouse retina.
1209. Simultaneous FMRI and Long-Term in Vivo Electrochemistry (LIVE): Identifying the Neurochemical
Correlates of Functional Imaging Signals
John Lowry 1 , Karen Griffin 2 , Stephen McHugh 3 , Nicola Sibson 4
1 Department of Chemistry, National University of Ireland, Maynooth, Ireland; 2 University College Dublin, Ireland; 3 Department of
Experimental Psychology, University of Oxford, Oxford, United Kingdom; 4 Gray Institute for Radiation Oncology and Biology,
University of Oxford, Oxford, Oxfordshire, United Kingdom
Long-term in-vivo electrochemistry (LIVE) enables real-time measurement of brain metabolites. Here we have simultaneously obtained BOLD fMRI and
amperometric LIVE tissue oxygen data from rat cerebral cortex, during both increases and decreases in inspired oxygen. BOLD and tissue oxygen
measurements demonstrated close correlation during both complete oxygen removal (negative responses) and increases in inspired oxygen (positive
responses). Our findings demonstrate the feasibility of obtaining real-time metabolite information during fMRI acquisition. The results show that the BOLD
signal provides a close correlate of the tissue oxygen dynamics or, alternatively, that tissue oxygen concentration can predict the magnitude of the BOLD
response.
1210. Evaluation of Cerebral Energy Demand During Graded Hypercapnia
Stefan Alexandru Carp 1 , Maria Angela Franceschini 1 , David Alan Boas 1 , Young Ro Kim 1
1 Martinos Center/Radiology, Massachusetts General Hospital, Charlestown, MA, United States
The cerebral metabolic rate of oxygen (CMRO 2 ) is a physiological parameter closely linked to neural activation as well as to various disease states.
Hypercapnic calibration is used to calibrate the BOLD-CBF-CBV relationship under the assumption of iso-metabolic blood flow increase during CO 2
inhalation. Simultaneous near infrared optical measurements of cerebral blood volume, blood flow and oxygen extraction can also be used to monitor
CMRO 2 changes, albeit at low spatial resolution. We use these optical measurements during graded hypercapnia to test the iso-metabolic assumption, and
demonstrate an apparent increase in brain metabolism at higher inhaled CO 2 levels.
1211. Dissociation of BOLD and Local Field Potentials
Wen-Ju Pan 1 , Matthew Magnuson 1 , Garth Thompson 1 , Waqas Majeed 1 , Dieter Jaeger 2 , Shella Keilholz 1
1 BME, Georgia Institute of Technology / Emory University, Atlanta, GA, United States; 2 Biology, Emory University, Atlanta, GA,
United States
To examine what extent consistence of the measurements between BOLD fMRI and local field potential (LFP), we evaluated BOLD and LFP
simultaneously in rat somatosensory cortex with a combined measurement technique. The preliminary results indicated a dissociation between BOLD and
LFP during low-level neural activity, which might mirror the limitation of neurovascular coupling, the bridge between BOLD and neural activity.
1212. TR and TE Dependence on Low Frequency BOLD Fluctuations
Matthew Evan Magnuson 1 , Wenju Pan 1 , Waqas Majeed 1 , Garth Thompson 1 , Shella Keilholz 1
1 Biomedical Engineering, Georgia Institute of Technology / Emory University, Atlanta, GA, United States
Low freqnecy fluctuations in resting state BOLD data have often been used to map functional connectivity in the rat brain. These low frequency BOLD
fluctuations contain contributions from CBF, CBV, and CMRO2. Each of these components have unique physiological time signatures and effective echo
times; therefore, modification of the TR and TE used in resting state scans should result in altered contributions from each BOLD component. In this study
we examine the dependence of the selection of the TR and TE variables on low frequency resting state data.