TRADITIONAL POSTER - ismrm

Poster Sessions
response of the brain to a visual stimulation paradigm specifically designed to partly disentangle spiking and synaptic activity within the primary visual
cortex. Our results, though preliminary, confirm that the energetics of the stimulated brain contains more information than that revealed by fMRI alone,
thereby indicating an uncoupling between hemodynamics and metabolism upon brain activation.
1119. Decrease of Deoxy-Hemoglobin Containing Blood Volume in Activated Human Visual Cortex
Xiang He 1 , Dmitriy A. Yablonskiy 1
1 Mallinckrodt Institute of Radiology, Washington University in St Louis, School of Medicine, St. Louis, MO, United States
Quantification of brain hemodynamic parameters during functional activation is essential for understanding biophysical mechanisms behind blood
oxygenation level depend (BOLD) phenomenon. Models of BOLD signal are often derived based on a relationship established by PET studies between
cerebral blood volume (CBV) and cerebral blood flow (CBF), ignoring that only portion of CBV - deoxyhemoglobin-containing blood volume (DBV)
affects BOLD signal. In this study, we directly measure DBV during visual activation in human visual cortex area using qBOLD-fMRI technique. We
demonstrate for the first time that DBV decreases during functional activation – an effect opposite to well known increase in CBV.
1120. Investigating the Origins of the DfMRI Signal Using 4 Tesla
R.Allen Waggoner 1 , Keiji Tanaka 1 , Kang Cheng 1,2
1 Laboratory for Cognitive Brain Mapping, RIKEN-BSI, Wako-shi, Saitama, Japan; 2 fMRI Support Unit, RIKEN-BSI, Wako-shi,
Saitama, Japan
Recent DfMRI studies preformed at 3T have observed an increase in the fractional BOLD signal change with increasing b value during functional
stimulation. The origin of this effect remains controversial with both cell swelling and vascular sources being offered as explanations. If this effect is truly
due to cell swelling, increasing the static magnetic field will not alter the effect. We present DfMRI results obtained at 4T which shows a constant BOLD
signal change with increasing b value. This result is consistent with a vascular source for a varying DfMRI response with diffusion weighting seen at 3T.
1121. Modeling The Non-Neuronal Contribution To The Blood Oxygenation Level Dependent Fmri Signal
Oscillations
Mauro DiNuzzo 1 , Federico Giove 1,2 , Bruno Maraviglia 1,2
1 Physics, Sapienza University of Rome, Rome, RM, Italy; 2 MARBILab, "Enrico Fermi" Center, Rome, RM, Italy
Resting oscillatory patterns in cortical activity can originate by both network- and metabolism-related mechanisms. In particular, recent evidences suggest
that the cell metabolic state exert an indirect control over the intrinsic network responsivity of the brain, much likely via astrocytic intracellular calcium
(Ca2+)-mediated gliotransmission. Here we examined theoretically the contribution of astrocytes in the generation of the fMRI signal changes in the absence
of focal neuronal stimulations. We found that oscillations in brain electrical, metabolic and vascular activity, as revealed by BOLD fMRI, can be
qualitatively and quantitatively explained by calcium-mediated coupling between neuroglial activation and metabolism.
1122. Diffusion Parameter Changes in White Matter Induced by Direct Intracortical Stimulation in Rats
Umesh Suryanarayana Rudrapatna 1 , Maurits P. van Meer 1 , Annette van der Toorn 1 , Rick M. Dijkhuizen 1
1 Image Sciences Institute, University Medical Center, Utrecht, Netherlands
While existing functional MRI techniques can reliably detect stimulus-induced activation in gray matter, activity in white matter regions has not been readily
measured. A recent study has reported subtle increases
in fractional anisotropy (FA) in specific white matter pathways in response to motor or visual stimulation in human subjects. In the current study, we aimed
to validate these findings with a direct cortical stimulation paradigm in rats. Our functional DTI approach revealed significant but variable FA changes in
restricted corpus callosum regions, which demonstrates that functional DTI enables detection of white matter activity in response to cortical stimulation.
1123. Whole-Brain Mapping of Venous Vessel Size in Humans Using the Hypercapnia-Induced BOLD Effect
Thies Halvor Jochimsen 1,2 , Dimo Ivanov 2 , Derek V M Ott 2 , Wolfgang Heinke 3 , Robert Turner 2 , Harald E.
Möller 2 , Jürgen R. Reichenbach 1
1 Medical Physics Group, Department of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany; 2 Max
Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany; 3 Department of Anesthesiology and Intensive Care
Medicine, University of Leipzig, Medical Faculty, Leipzig, Germany
It is demonstrated that non-invasive mapping of the venous microstructure (vessel radius) is possible by using the hypercapnia-induced BOLD effect.
Furthermore, it is shown that maps of venous blood volume and vessel density can be obtained from the same experimental setup. These parameters are
important for characterizing tumor angiogenesis and type.
1124. Characterization of the BOLD Hemodynamic Response Function at 7T: Towards Separation of
Vasculature and Parenchyma
Jeroen Cornelis Siero 1 , Natalia Petridou 2,3 , Johannes Marinus Hoogduin 2 , Nick F. Ramsey 1
1 Rudolf Magnus Institute, University Medical Center Utrecht, Utrecht, Netherlands; 2 Radiology, University Medical Center Utrecht,
Utrecht, Netherlands; 3 SPMMRC, University of Nottingam, Nottingam, United Kingdom
A limitation of T2*w BOLD fMRI is the confounding contribution of signal from the larger vasculature. Based on time-to-peak and full-width-at-halfmaximum
BOLD characteristics of different vascular compartments identified at 3T, we characterized the spatio-temporal properties of the BOLD response
at 7T in the visual cortex using an event-related fMRI paradigm with short visual stimuli, high sampling rate, and multiple spatial resolutions. For the
smallest voxelsize a high time-to-peak spatial heterogeneity of the BOLD response was observed with fast responses localized in parenchyma. This opens
the possibility to use TTP to probe layer specific BOLD responses in the human brain.