Simon Gross¹, Christoph Barmet¹, Benjamin Emmanuel Dietrich¹, and Klaas Paul Prüssmann^1
1Department of Information Technology and Electrical Engineering, Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland

An NMR field probe based method for direct observation of longitudinal nuclear magnetization is presented. While conceptually simple, the technique is capable of measuring sample induced nanotesla field changes with a high temporal resolution. Geometrical considerations render the method robust against background field fluctuations and clock instabilities. As an example, the measurements of spin-lattice relaxation curves of six different liquid samples are shown. This technique is a valuable tool for fast and reliable material characterization for MR engineering and biomedical purposes.

Wei Li¹, Bing Wu¹, Alexandru V. Avram¹, and Chunlei Liu^1,2
1Brain Imaging & Analysis Center, Duke University, Durham, North Carolina, United States, ²Radiology, Duke University, Durham, North Carolina, United States

Frequency shift and susceptibility from gradient-echo MRI shows excellent gray and white matter contrast, both of which depend on white matter fiber orientation. In this work, we explored the molecular underpinnings of orientation dependence of susceptibility in brain white matter. A biophysical model is developed to link the molecular susceptibility anisotropy of myelin components to the MRI-determined bulk anisotropy. This model provides a consistent interpretation of the orientation dependence of macroscopic magnetic susceptibility and the microscopic origin of anisotropic susceptibility. The results suggested that the cylindrically aligned lipid molecules in myelin are the main source of bulk susceptibility anisotropy.

Samuel James Wharton¹, and Richard Bowtell^1
1Sir Peter Mansfield Magnetic Resonance Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom

There is an ongoing debate about the source of the small difference in the frequency of signals from cortical grey matter (GM) and adjacent white matter (WM) that is manifested in phase images of the human brain. Recently, it was shown that the evolution of the phase with TE in WM is non-linear. Here, we assess the contribution of this non-linear phase evolution to the average GM/WM frequency difference at 7 T. The results show that non-linear phase effects may be the dominant source of the GM/WM frequency difference seen in phase images acquired using long echo times (> 17ms).

Jianfeng Bao¹, Xiaohong Cui¹, Zhenyao Zheng¹, Congbo Cai¹, and Zhong Chen^1
1Department of Electronic Science, Fujian Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, Fujian, China

Brown adipose tissue (BAT) has been found to be potential to combat against obesity and related diseases in adults, and has become a focus in biological and medical fields again. However, it is difficult to image BAT directly in vivo, especially when BAT mixes with other tissues. Here, we proposed a new method combining intermolecular double-quantum coherence with Dixon technique to map BAT only. The simulation and experimental results show that BAT can be imaged successfully at cellular scale. This new method may be significant in exploring the dynamic process of BAT in combating obesity.

Bo Zhu^1,2, Thomas Witzel¹, Shan Jiang³, Daniel G Anderson³, Robert S Langer³, Bruce R Rosen^1,2, and Lawrence L Wald^1
1Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, United States,²Harvard-MIT Health Sciences and Technololgy, Massachusetts Institute of Technology, Cambridge, MA, United States, ³Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA, United States

Detailed characterization of a contrast mechanism for imaging iron oxide contrast agents is presented, whereby the rotary saturation effect produces tunable signal changes as oscillating magnetic fields generated from vibrating iron oxide nanoparticles resonantly alter the signal in the spin-lock sequence. These signal changes only occur near the vibrating iron oxide agents, selectively localizing their presence. We characterize the the signal changes as a function of vibrational displacement of the contrast agent, duration of spin-lock time, and spin-lock frequency. The measured dependencies indicate desirable regimes of operation for any system using rotary saturation to detect vibrating agents.

Ana-Maria Oros-Peusquens¹, Andreas Matusch¹, Johannes Lindemeyer¹, Johanna Sabine Becker², and N. Jon Shah^1
1INM-4, Research Centre Juelich, Juelich, Germany, ²Central Division of Analytical Chemistry, Research Centre Juelich, Juelich, Germany

The origin of T2* and phase contrast in the rat brain and their changes following formalin fixation were investigated by comparison of MR-based maps with element analysis. Element images were obtained from two cryocut half-brain slices (one half native tissue, one half fixed, obtained from the same animal) using Laser Ablation Inductively Coupled Mass Spectrometry. No changes in the Fe, C, P and Cu distributions was observed following fixation. In contrast, the levels of Na, Mg, Cl, K, Mn, Zn change substantially. Qualitatively, a good correspondence between Fe and T2*/phase contrast is observed both in native and fixed tissue.

Fu-Nien Wang¹, Chin-Tien Lu¹, Shin-Lei Peng¹, and Tzu-Chen Yeh^2
1Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu, Taiwan, ²Department of Medical Research and Education, Taipei Veterans General Hospital, Taipei, Taiwan

D₂O was first proposed as a novel contrast agent for ¹H MRI. Previously, D₂O was used for perfusion imaging by receiving the deuterium signal. In this study, we alternatively measured the ¹H signal reduction due to the replacement effect of deuterium. Because the signal sensitivity of ¹H is about 100 times larger than deuterium, the SNR could be substantially increased by using this imaging strategy. Phantom and small animal experiments were conducted to proof the concept. Due to the non-toxicity and non-radioactivity, the D₂O could be a potential contrast agent for clinical usage without the need of hardware upgrade.

Hyung Joong Kim¹, Woo Chul Jeong¹, Young Tae Kim¹, Chae Young Lim², Hee Myung Park², and Eung Je Woo^1
1Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi, Korea, Republic of, ²Veterinary Internal Medicine, Konkuk University, Seoul, Korea, Republic of

MREIT can provide conductivity information of suspicious tissue using a current-injection MRI technique. To support its clinical significance, we should demonstrate that the conductivity image provides meaningful diagnostic information that is not available from other imaging modalities. To investigate any change of electrical conductivity due to brain abscess, canine brains having a regional abscess model were scanned along with separate scans of canine brains having no disease model. Conductivity images shown in this study indicated that time-course variations of conductivity contrast between normal and abscess regions are distinguishable in a different way compared with conventional MR image techniques.

Christian Stehning¹, Tobias Voigt², Philipp Karkowski¹, and Ulrich Katscher^1
1Philips Research Europe, Hamburg, Germany, ²Philips Research, Aachen, Germany

MR-based Electric Properties Tomography (EPT) provides a noninvasive means to assess electric tissue properties, provides a framework for an accurate determination of local SAR, and a diagnostic parameter in oncology. We have employed a fast balanced SSFP sequence, which allows for abdominal imaging in a single breathhold. Phantom experiments and first in vivo conductivity scans in the liver of healthy adults are shown.

Daniel K. Sodickson^1,2, Leeor Alon^1,2, Cem Murat Deniz^1,2, Ryan Brown¹, Bei Zhang¹, Graham C. Wiggins¹, Gene Y. Cho^1,2, Noam Ben Eliezer¹, Dmitry S. Novikov¹, Riccardo Lattanzi^1,2, Qi Duan³, Lester A. Sodickson⁴, and Yudong Zhu^1,2
1Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, United States, ²Sackler Institute of Graduate Biomedical Sciences, New York University School of Medicine, New York, NY, United States, ³National Institutes of Health, Bethesda, MD, United States, ⁴Cambridge Research Associates, Newton, MA, United States

We introduce a new general approach to mapping the electrical properties of tissue or materials. Unlike prior MR-based techniques, Local Maxwell Tomography (LMT) is free of assumptions regarding RF phase and coil/field/magnetization structure. LMT solves simultaneously for key functions of the absolute RF phase distribution along with unknown permittivity and conductivity, using complementary information from the transmit and receive sensitivity distributions of multiple coils to resolve ambiguities. LMT, from which EPT may be derived as a special case, can operate at arbitrary field strength, with a wide range of coil designs, and free of errors associated with rapid field variation.