Ferdinand Schweser^1,2, Andreas Deistung¹, Berengar Wendel Lehr³, Karsten Sommer^1,4, and Jürgen R. Reichenbach^1
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

Wei Li¹, Bing Wu¹, and Chunlei Liu^1,2
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.

Ana-Maria Oros-Peusquens¹, Andreas Matusch², Johannes Lindemeyer³, Sabine Johanna Becker⁴, and Nadim Jon Shah^1
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.

Bo Zhu^1,2, Thomas Witzel^1,2, Shan Jiang³, Daniel G. Anderson³, Robert S. Langer³, Bruce R Rosen^1,2, and Lawrence L Wald^1,2
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.

Jing Yuan¹, and Yi-Xiang Wang^1
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.

Astrid L.H.M.W. van Lier¹, Tobias Voigt², Ulrich Katscher², and Cornelis A.T. van den Berg^1
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.

Xiaotong Zhang¹, Pierre-Francois Van de Moortele², Sebastian Schmitter², and Bin He^1
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.

Tobias Voigt¹, Ole Väterlein², Christian Stehning¹, Ulrich Katscher¹, and Jens Fiehler^2
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.

Christian Stehning¹, Tobias Ratko Voigt², and Ulrich Katscher^1
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.