Joint Annual Meeting ISMRM-ESMRMB 2014 10-16 May 2014 Milan, Italy

Normal Brain Physiology by BOLD

Thursday 15 May 2014
Silver  10:30 - 12:30 Moderators: Mashiro Ida, M.D., Bum-Soo Kim, M.D.

10:30 0750.   
Regional Differences in the 7T BOLD-CVR Response to Ramped Hypercapnic Stimulus Suggest Pressure/Flow dependent Signal Properties
Alex Bhogal1, Marielle Philippens2, Jeroen C.W. Siero1, Esben Petersen1, Joe Fisher3, Peter Luijten1, and Hans Hoogduin1
1Radiology, University Medical Center, Utrecht, Netherlands, 2Radiotherapy, University Medical Center, Utrecht, Netherlands, 3Anaesthesia & Physiology, University Health Network, Toronto, Ontario, Canada

Here we examine differences in the cerebrovascular reactivity (CVR) response of gray and white matter to a progressive hypercapnic stimulus. Tissue-specific differences arise which cannot be explained by CVR response delay alone.

10:42 0751.   
Prospects for rapid CMRO2 quantification with interleaved TRUST, susceptometry-based oximetry, and phase-contrast MRI
Zachary B Rodgers1, Erin K Englund1, Michael C Langham1, and Felix W Wehrli1
1Radiology, University of Pennsylvania, Philadelphia, PA, United States

Susceptometry-based oximetry (SBO) and T2-Relaxation-Under-Spin-Tagging (TRUST) are two promising methods for global CMRO2 quantification. However, while SBO offers high temporal resolution, it is sensitive to vessel geometry and requires robust background field removal. TRUST does not have such limitations, but suffers from inherently low temporal resolution and must quantify flow from a separate PC-MRI measurement. By inserting a flow-encoded, SBO pulse sequence within the T1 recovery period of TRUST and using fewer effective echo times for T2 fitting, we demonstrate that it is possible to achieve T2-based CMRO2 quantification in only seconds, while directly comparing SBO- and T2-derived Yv.

10:54 0752.   
Regional quantification of cerebral venous oxygenation from MRI susceptibility mapping during hypercapnia
Audrey P Fan1,2, Karleyton C Evans1,3, Jeffrey N Stout2,4, Bruce R Rosen2,4, and Elfar Adalsteinsson1,4
1Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Charlestown, MA, United States, 3Psychiatry, Massachusetts General Hospital, Boston, MA, United States, 4Health Sciences and Technology, Harvard-MIT, Cambridge, MA, United States

The purpose of the study was to validate regional measurements of oxygen extraction fraction (OEF) in individual cerebral veins derived from quantitative susceptibility mapping. Flow-compensated gradient echo images and arterial spin labeling perfusion images were acquired during eucapnia and moderate hypercapnia in eight healthy volunteers. Regional changes in perfusion were used to predict local oxygenation changes and compared with quantitative susceptibility mapping (QSM)-based OEF estimates in veins draining the cingulate, occipital, parietal, and frontal cortices. Measured OEF changes during hypercapnia from MR susceptibility show good agreement with predictions based on regional flow observations and no change in the cerebral metabolic rate of oxygen CMRO2, and suggests that regional estimates of OEF in vessels from QSM maps are reliable.

11:06 0753.   Normalizing cerebrovascular reactivity map via concomitant CO2 and O2 challenge
Peiying Liu1, Yang Li1, and Hanzhang Lu1
1Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States

Cerebrovascular reactivity (CVR), measured by combining BOLD MRI and hypercapnia, is an important marker of cerebrovascular function. An undesirable feature of current CVR mapping results is that the image shows very strong contrast in large drains due to large blood volume in these voxels, which reduces the conspicuity of true CVR abnormalities. The present work demonstrates that normalizing CO2-CVR by O2-reactivity can effectively reduce the influence of cerebral blood volume on the results. Furthermore, a novel breathing paradigm with concomitant CO2/O2 challenge is developed to obtain CO2 and O2 reactivity maps in a single scan without increasing the study duration.

11:18 0754.   Modeling the hemodynamic response in stimulus-evoked mouse fMRI
Felix Schlegel1, Aileen Schroeter1, and Markus Rudin1,2
1Institute for Biomedical Engineering, ETH and University of Zürich, Zürich, Zürich, Switzerland, 2Institute of Pharmacology and Toxicology, University of Zürich, Zürich, Zürich, Switzerland

For stimulus-evoked fMRI in mice, the standard analysis tools may not be appropriate as the intrinsic assumptions of linearity relating stimulus and hemodynamic response and the use fixed shapes of the hemodynamic response function (HRF) may not be valid. Here, we show how the sensitivity and specificity of BOLD fMRI in mice can be improved by employing appropriate experimental designs and analysis approaches. We found that in out data, event-related designs produce more specific responses than block designs and that nonlinear regression approaches outperform traditional methods like finite impulse responses, SPM basis functions or fixed HRF shapes.

11:30 0755.   Face and Body Selective Regions of the Marmoset Extrastriate Visual Cortex
ChiaChun Hung1,2, Cecil Chern-Chyi Yen1, Jennifer L Ciuchta1, Daniel Papoti1, David A Leopold2, and Afonso C Silva1
1CMU/LFMI/NINDS, National Institutes of Health, Bethesda, MD, United States, 2SCNI/LN/NIMH, National Institutes of Health, Bethesda, MD, United States

The ventral temporal cortex of humans and macaques is marked by multiple, distinct regions specialized for the visual processing of faces and bodies. Here we demonstrate a similar category-specific organization in the common marmoset (Callithrix jacchus), a small, New World monkey. By using functional magnetic resonance imaging (fMRI) and electrocorticography (ECoG) in awake, trained animals, we demonstrate six face-selective and three adjacent body-selective cortical regions in the marmoset visual cortex. These findings suggest that key elements of ventral stream specialization for face and body processing were present in a common anthropoid primate ancestor at least 35 million years ago.

11:42 0756.   Dynamic modelling of layer specific cortical temperature for quantitative fMRI
Anna Gaglianese1,2, Peter Herman1, Daniel Coman1, Pietro Pietrini2,3, and Fahmeed Hyder1,4
1Department of Diagnostic Radiology - Magnetic Resonance Research Center, School of Medicine, Yale University, New Haven, CT, United States,2Laboratory of Clinical Biochemistry and Molecular Biology, Department of Surgical, Medical, Molecular Pathology and Critical Area, University of Pisa, Pisa, Italy, 3Clinical Psychology Branch, Pisa University Hospital, Pisa, Italy, 43Department of Biomedical Engineering, School of Engineering and Applied Science, Yale University, New Haven, CT, United States

Characterizing the relationship between neurovascular and neurometabolic changes that occurs in the brain is crucial for fMRI measurements. Here, we developed a model that relates changes in temperature in space and time to layer specific variations of CBF, CBV and BOLD acquired with differente tecniques and CMR02 measured by calibrated MRI, under rest and stimulation. We estimated and measured temperature changes nearly 0.1 °C in the middle/lower layers in agreement with a tighter coupling between CBF and CMR02 during stimulation. Temperature mapping and fMRI measurements may provide an useful tool to measure metabolic and hemodynamic variations in the brain.

11:54 0757.   Prior feeding of fat modulates the cortical response to fat in the mouth in humans
Sally Eldeghaidy1,2, Luca Marciani3, Joanne Hort4, Tracey Hollowood4, Gulzar Singh5, Debbie Bush6, Tim Foster7, Andy J. Taylor4, Johanneke Busch8, Robin C. Spiller3, Penny A. Gowland2, and Susan T. Francis2
1Department of Physics, Faculty of Science, Suez Canal University, Ismailia, Egypt, 2Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom, 3Nottingham Digestive Diseases Centre, University of Nottingham, Nottingham, United Kingdom, 4Flavour Research Group, Division of Food Sciences, University of Nottingham, Nottingham, United Kingdom, 5School of Biomedical Sciences, University of Nottingham, Nottingham, United Kingdom, 6Division of Surgery, Queen's Medical Centre University Hospital, Nottingham, United Kingdom, 7Division of Food Sciences, University of Nottingham, Nottingham, United Kingdom, 8Unilever Food and Health Research Institute, Unilever R&D, Vlaardingen, Netherlands

We investigated the modulation of BOLD responses to fat and control samples following prior feeding of a fat and water meal. The BOLD response in the anterior insula following consumption of the fat meal was suppressed compared to the water meal, with an increased rate of habituation to samples. Significant habituation was also seen in the amygdala, mid- and posterior insula. A decrease in reward and oral somatosensory activity was seen with increasing CCK and fullness values. These changes were found to be associated with a baseline reduction in CBF in the hypothalamus, thalamus and insula following the fat meal.

12:06 0758.   Relating resting-state fMRI and EEG brain connectivity across frequency bands
Fani Deligianni1, Maria Centeno1, David W. Carmichael1, and Jonathan D. Clayden1
1Institute of Child Health, UCL, London, United Kingdom

It has been shown that the resting-state (rs) networks observed with fMRI reflect electrophysiological activity. However, questions remain regarding which EEG features most closely reflect rs-fMRI networks. We relate the covariance structure of the envelope of the source localised electrophysiological signal to the covariance derived from rs-fMRI. We use statistical inference to predict EEG brain connectivity from fMRI connectivity and vice-versa. Our results support that the β band EEG activity best reflects spontaneous cognitive operations during conscious rest. Furthermore, fMRI connectivity can be predicted from EEG in any band indicating that there are signatures of rs-fMRI dynamics across EEG frequencies.

12:18 0759.   Deactivation of the default mode network is associated with resting-state glutamate and GABA
Yuzheng Hu1, Xi Chen1, Hong Gu1, and Yihong Yang1
1Neuroimaging Research Branch, National Institute on Drug Abuse, NIH, Baltimore, MD, United States

The default mode network (DMN) deactivation observed with BOLD fMRI is thought to be associated with suppression of spontaneous brain activities and reallocation of resources to ongoing, attention-demanding tasks. However, the underlying neurochemical mechanism of DMN deactivation remains largely unknown. The current study aimed to examine the relationship between DMN deactivation induced by a WM task and the endogenous concentrations of glutamate and GABA in the posterior cingulate/precuneus region. The major excitatory neurotransmitter, glutamate, was found to prevent BOLD signal from deactivation while GABA, the major inhibitory neurotransmitter, exert opposite effects.