fMRI: Novel Contrasts & Techniques
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Tuesday 8 May 2012
Room 212-213  16:00 - 18:00 Moderators: Ravi S. Menon, Jonathan R. Polimeni

16:00 0325.   
Functional Quantitative Susceptibility Mapping (fQSM)
David Z Balla1,2, Rosa M Sanchez-Panchuelo2, Sam Wharton2, Gisela E Hagberg3, Klaus Scheffler1,4, Sue T Francis2, and Richard W Bowtell2
1High-Field MR Centre, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany, 2Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom, 3Physiology of Cognitive Processes, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany,4Department of Neuroimaging and MR-Physics, University of Tuebingen, Tuebingen, Germany

Quantitative susceptibility mapping (QSM) was performed on fMRI time-series to reconstruct maps with activation induced local susceptibility changes. A multi-step image processing algorithm was developed for filtering out unwanted temporal and spatial signal variations. The method was validated on GE-EPI BOLD-fMRI datasets acquired at 7T with 1mm isotropic resolution during the application of visual, motor and somatosensory activation paradigms. Series of high-quality phase and susceptibility maps with minimal temporal noise were reconstructed, which resulted in activation maps corresponding to estimations from the modulus data. Functional QSM (fQSM) allows for quantification of the BOLD-effect for any time-series with phase information.

16:12 0326.   Functional MRI with SWIFT
Silvia Mangia1, Ryan Chamberlain1, Federico De Martino1,2, Steen Moeller1, Curt Corum1, Tae Kim3, Chaitanya Kalavagunta1, Shalom Michaeli1, Michael Garwood1, Seong-Gi Kim3, and Kamil Ugurbil1
1CMRR - Dept. of Radiology, University of Minnesota, Minneapolis, Minnesota, United States, 2Department of Cognitive Neuroscience, University of Maastricht, Maastricht, Netherlands, 3Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

We applied in fMRI sweep imaging with Fourier transformation (SWIFT), which measures fast 3D brain coverage without producing echoes. The SWIFT signal increased in the human visual cortex by 3-5% during visual stimulation at 4T. In vitro, no MRI contrast was observed with SWIFT on 5-mm tubes containing arterial or venous blood. However, the SWIFT signal decreased in the rat cortex during respiratory challenges at 9.4T, in spite of the local blood flow increase, thus likely reflecting decreased blood oxygenation in vivo. Other cellular events occurring during activation might contribute to the SWIFT functional contrast in addition to oxygenation changes.

16:24 0327.   
Human functional imaging at 9.4 T: Spin echo and gradient echo EPI
Juliane Budde1, G. Shajan1, Maxim Zaitsev2, Klaus Scheffler1, and Rolf Pohmann1
1Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany

Functional images with a finger tapping task were acquired using spin echo and gradient echo EPI sequences at 9.4 T with isotropic resolution of 1 mm. Resulting activation was registered onto high-resolution anatomic images. A mask of veins was identified; activated voxels were divided into ‘venous’ and ‘non-venous’, and averaged over subjects, voxels, and blocks. Activation levels were 6.1 ± 5.4 % in non-venous and 9.1 ± 5.7 % in venous locations. Time courses for the spin echo EPI are very similar and show an activation level of 3.9 ± 7.2 % outside and 4.2 ± 7.0 % inside veins.

16:36 0328.   
MR-Encephalography using a Spherical Stack of Spirals Trajectory
Jakob Assländer1, Marco Reisert1, Benjamin Zahneisen1, Thimo Hugger1, and Jürgen Hennig1
1Dep. of Radiology, Medical Physics, University Medical Center, Freiburg, Baden-Württemberg, Germany

A spherical stack of spirals trajectory for fast single shot 3D-imaging is presented. Contrary to a shell trajectory, in a stack of spirals trajectory off-resonance leads to distortions rather than blurring and signal dropout. Latter one is hard or impossible to correct for. It is shown, that the off-resonance behavior strongly depends on the direction of the acquisition. Furthermore the stack of spirals easily allows a reduction of the FOV in z-direction to save acquisition time. This can be used to increase the resolution.

16:48 0329.   
Distortion-free high-resolution fMRI at 9.4 T
Philipp Ehses1,2, Juliane Budde1, G. Shajan1, and Klaus Scheffler1,2
1Max Planck Institute for Biological Cybernetics, Tübingen, Germany, 2Dept. for Neuroimaging, University Hospital Tübingen, Tübingen, Germany

SNR benefits allow for significantly higher resolution in BOLD fMRI at ultra-high fields. On the flip side, faster T2* relaxation leads to blurring and increased B0 field inhomogeneities aggravate distortion artifacts in EPI BOLD imaging at higher fields. In this work, a single-echo gradient-echo sequence is presented, that is optimized for high BOLD SNR by combining the concept of echo-shifting with an interleaved slice order. The method is demonstrated in finger tapping experiments on a human 9.4T system. The result is a BOLD activation map with 1mm isotropic resolution virtually free from distortions.

17:00 0330.   SE fMRI in human bilateral auditory cortex using B1 shimming
Federico De Martino1,2, Sebastian Schmitter1, Kamil Ugurbil1, Elia Formisano2, Essa Yacoub1, and Pierre-Francois van de Moortele1
1Radiology, Center for Magnetic Resonance Research, Minneapolis, Minnesota, United States, 2Cognitive Neuroscience, Maastricht University, Maastricht, Netherlands

We aim at using SE-fMRI to push further the investigation of functional organization in the human auditory cortex. To do so we investigate the use of an RF coil that includes 8 Transceivers (8TCx), allowing for the use of B1 shimming over right and left auditory cortices, as well as 24 Receive only channels (24Rx), providing higher SNR. We demonstrate successful SE-fMRI in bilateral auditory cortex at 7T highlighting significant differences between responses to voice vs. non-voice stimuli in anterior areas of the superior temporal sulcus and gyrus.

17:12 0331.   Slab-Selective, BOLD-Corrected VASO (SS-VASO) in Human Brain at 7T
Laurentius Huber1, Dimo Ivanov1, Markus Streicher1, and Robert Turner1
1Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany

To understand human brain neural activity it is helpful to study direct physiological variables, such as cerebral blood volume (CBV). Vascular space occupancy (VASO) is a non-invasive fMRI method that measures change in CBV. VASO at 7 T is limited by low signal and BOLD contamination. Here we present a slab-selective, BOLD-corrected SS-VASO variant that avoids these problems, and provides reliable CBV changes in vivo with high sensitivity. Temporal and spatial properties of BOLD and VASO signal are directly compared.

17:24 0332.   
A quantitative spatial comparison of high-density diffuse optical tomography and fMRI mapping of visual cortex
Adam T Eggebrecht1, Brian R White1, Silvina L Ferradal1,2, Chunxiao Chen3, Yuxuan Zhan4, Abraham Z Snyder5,6, Hamid Dehghani7, and Joe P Culver8,9
1Radiology, Washington University School of Medicine, St Louis, MO, United States, 2Biomedical Engineering, Washington University in St. Louis, St Louis, MO, United States, 3Department of Biomedical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing, Jiangsu, China, 4School of Computer Science, University of Birmingham, 5Radiology, Washington University School of Medicine, 6Neurology, Washington University School of Medicine, St Louis, MO, United States, 7School of Computer Science, University of Birmingham, United Kingdom, 8Radiology, Washington University School of Medicine, Saint Louis, MO, United States, 9Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, United States

fMRI has commanded a dominant role in current neuroscience research, yet its use in neuro-scientific or bedside clinical studies has been limited because the current tools lack the combination of being portable while maintaining moderate resolution and localization accuracy. Optical neuroimaging overcomes these obstacles, but, until recent advancements in high-density diffuse optical tomography (HD-DOT), has been hampered by limited resolution. We evaluate the image-quality of HD-DOT against fMRI using functional maps of the visual cortex as a benchmark and quantify localization error with center-of-mass and phase metrics. This work provides support for adoption of HD-DOT as a surrogate for fMRI.

17:36 0333.   
Simultaneous small animal PET/MR in activated and resting state reveals multiple brain networks
Hans F Wehrl1, Konrad Lankes1,2, Mosaddek Hossain1, Ilja Bezrukov1,3, Chih-Chieh Liu1, Petros Martirosian4, Gerald Reischl1, Fritz Schick4, and Bernd J Pichler1
1Department for Preclinical Imaging and Radiopharmacy, University of Tuebingen, Tuebingen, Germany, 2Bruker BioSpin MRI, Ettlingen, Germany, 3Max Planck Institute for Intelligent Systems, Tuebingen, Germany, 4Section on Experimental Radiology, University of Tuebingen, Tuebingen, Germany

Simultaneous small animal PET/MR allows the study of functional processes on multiple levels. Here we present a comparison between simultaneous activation as well as resting state fMRI and PET in rats. Additional activated components of brain networks are found in PET, not present in fMRI. The data show complementarities of both techniques in respect to activation as well as default mode network imaging in the brain.

17:48 0334.   
Enhanced fMRI Sensitivity using CBV based Contrast with the Blood Pool USPIO Agent Ferumoxytol in Humans
Deqiang Qiu1, Greg Zaharchuk1, Thomas Christen1, Wendy W Ni1, and Michael E Moseley1
1Radiology, Stanford University, Stanford, CA, United States

In this paper, we present the first human study of the use of ultrasmall superparamagnetic iron particle (USPIO) for contrast agent based blood Volume functional MRI (fBVI). The temporal response function of fBVI was characterized, and was found to include both a slow and a fast component. The contrast to noise ratio (CNR) of fBVI was found to be of up to a factor of 2.9 than the commonly used BOLD (Blood oxygenation level dependent) technique. The significant CNR gain with fBVI opens the possibility of high-resolution fMRI, including mapping of ocular orientation column in human.