Ultrahigh Field & High Resolution Neuroimaging
Monday 20 April 2009
Room 316BC 11:00-13:00


Joseph J. H. Ackerman and Kamil Ugurbil

11:00  42.

Investigating the Sources of Phase Contrast: Iron Oxide Nanoparticle Study to Exclude Deoxyhemoglobin as a Major Source for the Gray/white Matter Phase Contrast


Jongho Lee1, Yoshiyuki Hirano, Masaki Fukunaga1, Afonso Silva, Jeff H. Duyn1
Advanced MRI/LFMI/NINDS, National Institute of Health, Bethesda, MD, USA

    An intravascular contrast agent (iron oxide nanoparticle) was used to investigate the sources of phase contrast. The result indicates that deoxy-hemoglobin is not a major source for the white and gray matter contrast.
11:12 43.   

Susceptibility Weighted Imaging of the Human Brain at 9.4T


Juliane Sabine Budde1, Rolf Pohmann1, Gunamony Shajan1, Kâmil Ugurbil2
Magnetic Resonance Center, Max Planck Institute for Biological Cybernetics, Tuebingen, Germany; 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA

    Susceptibility weighted imaging benefits from ultra-high field in terms of increased contrast-to-noise ratio and SNR. High resolution phase images with up to 0.175mm x 0.175mm in-plane resolution were acquired at a 9.4T scanner using a 3D velocity compensated gradient echo sequence. The images, covering almost the whole brain area, show excellent susceptibility weighted contrast and SNR. Compared to 3T images with an in-plane resolution of 0.45mm x 0.50mm acquired in about the same scan time, a qualitative improvement can be observed and a greatly increased number of small veins can be visualized at 9.4T.
11:24 44. 

Presurgical Visualization of Cerebral Surface Veins with Susceptibility Weighted Imaging

    Zeinab Al-Rekabi1,2, Kelly McPhee3, Kevin Fitzpatrick3,4, Bruce Bjornson3,5, Alexander Rauscher3,6
University of British Columbia , Vancouver, BC, Canada; 2University of Ottawa, Ottawa, Ontario, Canada; 3University of British Columbia, Vancouver, BC, Canada; 4Children's Brain Mapping Centre, BC Children's Hospital; 5Children's Brain Mapping Centre, BC Children's Hospital and Child & Family Research Institute; 6UBC MRI Research Centre
    Susceptibility Weighted Imaging combines magnitude and phase of a high resolution fully flow-compensated 3D gradient echo scan, from which detailed images of the cerebral venous vasculature can be obtained without using a contrast agent. Due to the required high pass filtering of the phase, visualization of veins at the brain's surface has been poor. We used bilateral filtering to preserve vein related phase information at the brain's surface, by minimizing blurring across boundaries between brain and noise. A combination of resulting surface venograms with a structural scan provides images of the brains surface with venous vessels as landmarks for surgery.
11:36  45. 

Susceptibility and T2/T1 Weighted Contrast Enhancements in Rat Brain Using BSSFP at 9.4T


Joseph S. Gati1, L Martyn Klassen1, Robert Bartha1, Ravi S. Menon1
CFMM, Robarts Research Institute, London, Ontario, Canada

    Balanced steady-state free precession (bSSFP) pulse sequences have found widespread use at clinical field strengths, particularly for cardiac applications, because of short acquisition times, high contrast and increased signal to noise characteristics compared to similarly acquired gradient echo (GRE) methods. We have previously demonstrated there to be a greater than 3 times signal to noise advantage, per unit time, using a fully optimized bSSFP sequence over a similarly matched gradient echo acquisitions. The current study demonstrates unique image contrast at high magnetic field strength observed in both high resolution ex vivo and in vivo rat brain images.
11:48  46. 

Cortical Layers Imaging with Inversion Recovery MRI


Daniel Barazany1, Ory Levy1, Yaniv Assaf1
Department of Neurobiology, Tel Aviv University, Tel Aviv, Israel

    Cyto-architecture is a histological features that delineate the neuronal morphology of the tissue in general and layers in cortex in particular. Currently there is no in-vivo imaging modality that enables accurate and robust visualization of neuronal cell structures. In this work we use a multi-parametric MRI and clustering approach to segment the cortex into a laminar pattern based on multi-spectral inversion recovery dataset. This approach was implemented on the rat brain and compared with cyto-architectonic analysis; there is a good agreement between the MRI layers and histological identification of the layers. Similar results were also obtained on the human brain.
12:00 47. 

Within Gray and White Mater R2* Variations Correlate Histochemical Iron Stain of the Human Brain

    Masaki Fukunaga1, Jongho Lee1, Tie-Qiang Li, Kant K. Matsuda2, Hellmut Merkle, Peter van Gelderen1, Jacco A. de Zwart1, Jeff H. Duyn1
Advanced MRI/LFMI/NINDS, National Institutes of Health, Bethesda, MD, USA; 2Laboratory of Pathology/NCI, National Institutes of Health, Bethesda, MD, USA
    High resolution T2* weighted MRI at high field strength shows substantial contrast variation across laminae in cortical gray matter. This contrast variation also exist within cortical gray matter and subcortical white matter. In this work, to assess the contribution of non-heme iron and myelin in the R2* variations, we investigated the similarity of R2* map and histochemical stained image of the human brain. The contrast variation of R2* map highly corresponded to iron stain than myelin stain, it demonstrates that possible main contributor of R2* variation is non-heme iron.
12:12 48. 

Detection and Delineation of Focal Cortical Lesions in Patients with Focal Epilepsy: Preliminary Results at 7T and 3T with 32 Channel Phased Arrays


Neel Madan1, Thomas Benner2, Elizabeth Anne Thiele3, Emad N. Eskandar4, Lawrence L. Wald2,5, Patricia Ellen Grant1,2
Department of Pediatric Radiology, Massachusetts General Hospital, Boston, MA, USA; 2A.A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Boston, MA, USA; 3Pediatric Epilepsy Service, Department of Neurology, Massachusetts General Hospital, Boston, MA, USA; 4MGH-HMS Center for Nervous System Repair, Department of Neurosurgery, Massachusetts General Hospital, Boston, MA, USA; 5Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, USA

    Identification of focal cortical dysplasias (FCD) on MRI is critical in the management of patients with medically refractory epilepsy. In this study, four patients with known or suspected FCD were imaged at 7T and 3T with 32 channel phased array coils. High resolution imaging allowed characterization and delineation of tissue involvement in three of the patients. These two technologies complemented each other in defining lesion boundary and characterizing the involved tissue. Both 7T and 3T with 32 channel coil hold great promise as a problem solving tool for lesion identification in those patients with “MR negative” medically refractory epilepsy.
12:24 49. 

Three-Dimensional Segmentation of the Internal Structures of the Human Hippocampus  at 7 Tesla

    Marie Chupin1, Stephane Lehericy2,3, Olivier Colliot1, Malgorzata Marjanska4, Ute Goerke4, Kamil Ugurbil4, Pierre-Francois Van de Moortele4
CNRS UPR 640 - LENA, University Pierre and Marie Curie - Paris 6, Paris, France; 2Center for NeuroImaging Research, University Pierre and Marie Curie - Paris 6, Paris, France; 3Neuroradiology, Inserm U610, Pitie-Salpetriere Hospital, Paris, France; 4Center for Magnetic Resonance Research and Department of radiology, University of Minnesota, Minneapolis, MN, USA
    In this work, we used 7T whole body to image and segment in three dimension the internal structure of the human hippocampus. Three human volunteers were included. Six subparts of the hippocampus were clearly differentiated including the stratum pyramidale of the cornu ammonis (CA), more precisely the first 3 segments of CA (CA1-3), the hilum of the dentate (corresponding to the dentate proper and CA4), the subiculum, the alveus and the fimbria. Segmentation of the internal structure of the hippocampus at 7T provides new biomarkers that can be used in brain pathologies.
12:36 50.

Separation and Reproducibility of Touch Activations in Areas 3b and 1 Within the Primary Somatosensory Cortex by High Resolution FMRI at 7T


Elizabeth Ann Stringer1, Robert M. Friedman2, J Chris Gatenby1, Li Min Chen1, John C. Gore1
Institute of Imaging Science, Vanderbilt University, Nashville, TN, USA; 2Department of Psychology, Vanderbilt University, Nashville, TN, USA

    Ultra-high field fMRI provides greater sensitivity and increases spatial resolution, resulting in finer scale activity maps than at lower fields. Here, we test the feasibility of 7T fMRI to visualize millimeter resolution somatotopic maps in neighboring regions, Brodmann Areas 3b and 1, within the primary somatosensory cortex. Images were acquired using a 7T Philips Achieva scanner while innocuous air puffs were delivered to alternating digits. Repeated trials within single subjects showed reproducible topological activations within areas 3b and 1 of the primary somatosensory cortex. The data support findings from nonhuman primate studies.