New Contrast
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Monday May 9th
Room 511D-F  16:30 - 18:30 Moderators: Ludovic De Rochefort and Klaas Pruessmann

16:30 120.   SEMI-TWInS: Simultaneous Extraction of Myelin and Iron using a T2*-Weighted Imaging Sequence  
Ferdinand Schweser1,2, Andreas Deistung1, Berengar Wendel Lehr3, Karsten Sommer1,4, and Jürgen R. Reichenbach1
1Medical Physics Group, Dept. of Diagnostic and Interventional Radiology 1, Jena University Hospital, Jena, Germany, 2School of Medicine, Friedrich Schiller University of Jena, Jena, Germany, 3Medical Physics Group, Dept. of Diagnostic and Interventional Radiology, Jena University Hospital, Jena, Germany, 4School of Physics and Astronomy, Friedrich Schiller University of Jena, Jena, Germany

16:42 121.   In vivo Evidence of Susceptibility Anisotropy and Susceptibility Tensor Imaging of Human Brain 
Wei Li1, Bing Wu1, and Chunlei Liu1,2
1Brain Imaging & Analysis Center, Duke University, Durham, NC, United States, 2Radiology, Duke University, Durham, NC, United States

Previously, the magnetic susceptibility of brain tissue is generally assumed to be isotopic. Recently, emerging evidences from animal studies and in vitro brain specimens started to show the directionality of susceptibility. In this study, we demonstrated the evidence of magnetic susceptibility anisotropy from in vivo human brain by comparing susceptibility map with the diffusion tensor imaging results and comparing susceptibility obtained from different orientations. Further, the susceptibility tensor is calculated, which shows varied gray and white matter contrast among the three principal eigenvalues. These results provide convincing evidences that the magnetic susceptibility of in vivo human brain is anisotropic.

16:54 122.   Origin of phase contrast: insight from susceptibility, R2* and element imaging by LA-ICP-MS 
Ana-Maria Oros-Peusquens1, Andreas Matusch2, Johannes Lindemeyer3, Sabine Johanna Becker4, and Nadim Jon Shah1
1Institute of Neuroscience and Medicine (INM-4), Research Centre Juelich, Juelich, NA, Germany, 2INM-2, Research Centre Juelich, Germany, 3INM-4, Research Centre Juelich, Germany, 4ZCH, Research Centre Juelich

MR-based maps of susceptibility, field and R2* distribution were compared to element imaging using Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICP-MS). The distributions of carbon (C) and iron (Fe), elements thought to be the main determinants of susceptibility and phase contrast, show much more detail than the susceptibility and field maps obtained from MRI. A linear dependence between R2* and Fe concentration has been confirmed in a limited, ROI-based analysis. A clustering analysis of the distribution of 15 elements shows features which are unclear in the phase or susceptibility distributions but can be found in the mixed-contrast T2*-weighted high-resolution images.

17:06 123.   Active Contrast Modulation of Iron Oxide Nanoparticles using Rotary Saturation 
Bo Zhu1,2, Thomas Witzel1,2, Shan Jiang3, Daniel G. Anderson3, Robert S. Langer3, Bruce R Rosen1,2, and Lawrence L Wald1,2
1Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, MA, United States, 2Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States, 3Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States

A novel contrast mechanism for imaging iron oxide contrast agents is described based on the Rotary Saturation effect, whereby the oscillating magnetic fields generated from vibrating iron oxide nanoparticles resonantly couples with the spin system to produce tunable signal changes. We demonstrate this active contrast modulation with a block-design experiment interleaving vibration of the contrast agent on and off resonance relative to the rotating frame resonance frequency, and observe statistically significant signal changes only for ROIs adjacent to the nanoparticles. We envision contrast modulation of iron oxide nanoparticles in-vivo using sound waves or endogenous motion to generate the nanoparticle vibration.

17:18 124.   A General T1lower case Greek rho Relaxation Model for Spin-Lock MRI using a Rotary Echo Pulse 
Jing Yuan1, and Yi-Xiang Wang1
1Department of Imaging and Interventional Radiology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong

T1ñ relaxation was conventionally described to follow a purely monoexponential decay as a function of the spin lock time. However, the validity of this monoexponential decay may be violated in the presence of field inhomogeneities, especially at extremely low spin lock frequencies. T1ñ relaxation behavior using a rotary echo spin lock pulse was studied using the Bloch Equation and the rotation matrix transformation. A general analytical expression was derived to describe the T1ñ relaxation at different spin lock frequencies in the presence of B0 inhomogeneity, and verified experimentally by phantom and in vivo imaging from 50Hz to 500Hz.

17:30 125.   Comparing Electric Properties Tomography at 1.5, 3 and 7 T 
Astrid L.H.M.W. van Lier1, Tobias Voigt2, Ulrich Katscher2, and Cornelis A.T. van den Berg1
1Radiotherapy, UMC Utrecht, Utrecht, Netherlands, 2Philips Research Europe, Hamburg, Germany

Recently, the principle feasibility of Electrical Properties Tomography has been shown at different field strengths, 1.5T, 3T, and 7 T. To determine the optimal field strength for EPT, a systematic study was performed comparing phantom measurements and simulations. The influence of SNR and the error induced by using the transceiver phase instead of the transmit phase on the reconstruction are evaluated.

17:42 126.   Imaging Electrical Properties of the Human Brain using a 16-channel Transceiver Array Coil at 7T 
Xiaotong Zhang1, Pierre-Francois Van de Moortele2, Sebastian Schmitter2, and Bin He1
1Department of Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States, 2Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, United States

The electrical properties (EPs, conductivity and permittivity) of brain tissues provide important information for basic brain research and clinical diagnosis of neurological disorders. They also play an important role in SAR calculation. In this study, using a 16-channel transceiver array coil at 7T and based on existing B1-mapping technique, we have developed a novel method to estimate both magnitude and absolute phase distribution of transmit/receive B1 fields, and the electrical conductivity and relative permittivity values. We report our pilot results in a human brain for electrical property imaging using a high field MRI system.

17:54 127.   In vivo Glioma Characterization using MR Conductivity Imaging 
Tobias Voigt1, Ole Väterlein2, Christian Stehning1, Ulrich Katscher1, and Jens Fiehler2
1Philips Research Laboratories, Hamburg, Germany, 2Department of Neuroradiology, University Medical Centre Hamburg-Eppendorf, Hamburg, Germany

Conductivity imaging provides a new quantitative contrast for MRI. In the presented study conductivity imaging is applied in a routine clinical environment. First clinical results of glioma patients are reported and compared with healthy volunteers. In vivo conductivity of glioma is found considerably higher than healthy white matter conductivity.

18:06 128.   Real-Time Conductivity Mapping using Balanced SSFP and Phase-Based Reconstruction 
Christian Stehning1, Tobias Ratko Voigt2, and Ulrich Katscher1
1Philips Research Laboratories, Hamburg, Germany, 2Institute of Biomedical Engineering, University of Karlsruhe, Karlsruhe, Germany

A volumetric, real-time conductivity mapping method based on balanced SSFP and an image phase based reconstruction is presented. It provides sufficient temporal resolution to visualize the dissolving of salt in a water phantom.

18:18 129.   Panel Discussion
Richard W. Bowtell, Ludovic De Rochefort, Klaas Pruessmann & Daniel K. Sodickson