Electromagnetic Tissue Property Mapping: Challenges & Solutions

Wednesday 14 May 2014    16:00 - 17:00

Space 1/Power Poster Theatre & Traditional Poster Hall 
Moderators: Markus Barth, Ph.D. & Ulrich Katscher, Ph.D.

Click on this video icon to view the introductory session.

Russell Dibb^1,2, Luke Xie^1,2, and Chunlei Liu^3,4
1Center for In Vivo Microscopy, Duke University Medical Center, Durham, NC, United States, ²Biomedical Engineering, Duke University, Durham, NC, United States, ³Brain Imaging & Analysis Center, Duke University Medical Center, Durham, NC, United States, ⁴Radiology, Duke University Medical Center, Durham, NC, United States

The magnetic susceptibility of myocardium is anisotropic and is associated with myocardial organization. We determined the relationship between the magnetic susceptibility and the DTI-based fiber orientation of myocardial tissue. The origins of the observed bulk magnetic susceptibility anisotropy in myocardium can be related to the microscopic anisotropy of peptide bonds in myofibrillar proteins. In MRI, this susceptibility anisotropy is enhanced by the use of contrast agents. Given the high-resolution capability of gradient echo phase, imaging susceptibility anisotropy of the heart would aid in assessing myocardial fiber integrity and alterations induced by cardiac diseases and disorders.

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

Recent studies have shown that high quality phase sensitive inversion recovery (PSIR) data can be efficiently acquired at high magnetic field strengths using a 3D interleaved sequence in which two separate Turbo Field Echo (TFE) readouts are applied after each inversion pulse. We propose that the phase data associated with the second TFE readout of the PSIR sequence can be used to form 3D maps of magnetic susceptibility via the recently developed quantitative susceptibility mapping (QSM) technique. The results presented in this article demonstrate that T1-weighted anatomical images and iron-sensitive QSM data can be acquired simultaneously from a single scan.

Dongyoeb Han¹, Yoonho Nam¹, Sung-Min Gho¹, and Dong-Hyun Kim^1
1Yonsei University, Seoul, Korea

Susceptibility weighted imaging based on GRE provides enhancement of susceptibility difference which is useful for visualization of vein, micro-hemorrhage and iron deposition. However, GRE suffers from the macroscopic B0 inhomogeneity due to air/tissue boundary and this effect is shown as SNR loss both in magnitude and phase. Here, an improved algorithm for B0 field inhomogeneity compensated SWI, applicable to both magnitude and phase, is proposed using the 3D z-shim mGRE sequence.

Hongfu Sun¹ and Alan H. Wilman^1
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada

Quantitative susceptibility mapping can be done on ultra-fast EPI scans and susceptibility values of deep grey matter are similar to those from high resolution SWI scans.

Noam Shemesh¹, Gonzalo A Alvarez¹, and Lucio Frydman^1
1Chemical Physics, Faculty of Chemistry, Weizmann Institute of Science, Rehovot, Israel

DTI, STI and T2* are powerful methods for mapping orientations, yet they demand either diffusion path lengths that fully probe confining boundaries or the rotation of specimens about B0. Han et al recently proposed the internal-gradient-distribution-tensor (IGDT) as a novel source of orientational contrast. Here we develop a new, fully-refocused approach based on Non-uniform Oscillating-Gradient Spin-Echo (NOGSE) MRI for selectively probing these IGDT whilst keeping all other sources of decoherence – including diffusion, T2, pulse/timing/gradient imperfections and T1– constant. The approach is explained, and experiments in spinal cord segments reveal the possibility of using it for mapping WM orientations noninvasively.

Ferdinand Schweser¹, Edsel Daniel Peres Gomez¹, Andreas Deistung¹, and Jürgen R Reichenbach^1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

In a recent paper Liu and Li presented a novel MR phase-based technique to assess tissue anisotropy, in the following referred to as (multipole) Fourier spectrum Tensor Imaging (FTI). In this contribution we show that the microstructural anisotropy measured by FTI, though being derived from the MR phase, does neither specifically reflect magnetic susceptibility anisotropy (as STI does; e.g. due to myelin) nor does it require an anisotropic distribution of magnetic susceptibility inclusions at all.

Andreas Deistung¹, Martin Krämer¹, Ferdinand Schweser¹, and Jürgen Rainer Reichenbach^1
1Medical Physics Group, Institute of Diagnostic and Interventional Radiology I, Jena University Hospital - Friedrich Schiller University Jena, Jena, Germany

We present a non-invasive approach for characterizing the vasculature in the capillary regime with an effective in-plane resolution of 2mm at 3 Tesla by employing gradient echo sampling of FID and spin echo (GESFIDE) with periodically rotated overlapping parallel lines with enhanced reconstruction – echo planar imaging (PROPELLER-EPI). The analysis of the blood oxygenation level dependency related signal changes provoked by inhaling different gas mixtures (air, carbogen) resulted in quantitative maps of vessel radius, deoxygenated blood volume, and venous vessel density that enable discrimination of anatomic structures. Furthermore, average values across 23 equally-aged subjects are presented for different tissue types.

Luning Wang¹, William Potter², and Qun Zhao^1
1Department of Physics and Astronomy, University of Georgia, Athens, GA, United States, ²Laboratory of Plasma Studies, Cornell University, Ithaca, NY, United States

Along with the development of modern imaging technologies, contrast agents play increasingly important roles in both clinical applications and scientific researches. Super-paramagnetic iron oxide (SPIO) nanoparticle, a negative contrast agent, has been extensively used in magnetic resonance imaging (MRI), such as in vivo labeling and tracking of cells. However, there still remain many challenges, such as in vivo quantification of SPIO nanoparticles. In this work, a novel MR phase gradient based method was proposed to quantify the SPIO nanoparticles. As a calibration, a phantom experiment using known concentrations (50, 75, 100, and 125 µg/ml) of SPIO was first conducted to verify the proposed quantification method. In a following in vivo experiment, C6 glioma cells labeled with SPIO nanoparticles were implanted into flanks of four mice, which were scanned 1 to 3 days post-injection for in vivo quantification of SPIO concentration. The results showed that the concentration of SPIO nanoparticles can be determined in both phantom and in vivo experiments using the developed MR phase gradients approach.

Cynthia Wisnieff^1,2, Sriram Ramanan³, David Pitt³, John Olesik⁴, and Yi Wang^1,2
1Biomedical Engineering, Cornell University, Ithaca, New York, United States, ²Radiology, Weill Cornell Medical College, New York, New York, United States, ³Neurology, Yale University, New Haven, Connecticut, United States, ⁴Ohio State University, Ohio, United States

We assess the contributions of iron deposition and demyelination to the measured susceptibility of multiple sclerosis (MS) lesions in MRI. In this work we examine histological findings of the quantitative distribution of iron from laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), the distribution of demyelination from myelin basic protein (MBP) labeling, and susceptibility distribution from QSM. This preliminary study shows that the contribution to the total observed susceptibility change in MS lesion is from both the measured iron distribution in the lesion and demyelination in the center of the lesion.

Vanessa Wiggermann^1,2, Samantha Y.Y. Tan³, Enedino Hernández Torres^1,4, David K.B. Li^1,4, Alex L. MacKay^2,4, Irene M. Vavasour^1,4, Nicholas Seneca⁵, David Leppert⁵, Shannon Kolind^4,6, Anthony Traboulsee^4,6, and Alexander Rauscher^1,4
1Radiology, University of British Columbia, Vancouver, BC, Canada, ²Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada,³Science, University of British Columbia, Vancouver, BC, Canada, ⁴UBC MRI Research Centre, Vancouver, BC, Canada, ⁵F. Hoffmann-La Roche Ltd., Basel, Switzerland, ⁶Neurology, University of British Columbia, Vancouver, BC, Canada

Recent studies have exploited MR frequency shift mapping as a high-resolution tool to monitor changes in MS lesions. However, the origin of the observed changes in MR frequency is not yet fully understood. Here, we compared frequency shift imaging in 25 patients with two myelin sensitive MR techniques, magnetization transfer and myelin water imaging. Frequency shifts between different lesions types differed greatly and variability of frequency shifts within lesion types suggests that MR frequency aids in characterizing lesions at different stages of their development.

Sung-Min Gho¹, Jaewook Shin¹, David M Grodzki², and Dong-Hyun Kim^1
1Electrical and Electronic Engineering, Yonsei University, Sinchon-dong, Seoul, Korea, ²Siemens AG, Erlangen, Germany

MR imaging can provide information regarding the electric and magnetic properties of tissue (i.e. conductivity, and susceptibility). Various studies using these electrical conductivity and magnetic susceptibility properties were performed independently. In this abstract, we propose a new method for performing three applications (i.e. conductivity mapping, short TE QSM, QSM) simultaneously using double-echo UTE sequence. From the first echo data, we acquired conductivity maps and short TE QSM, and from the second echo data, QSM was obtained.

Chunlei Liu^1,2, Wei Li¹, and Ioannis Argyridis^1
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, ²Radiology, Duke University, Durham, NC, United States

A method was proposed and demonstrated to measure electric conductivity using eddy currents induced by pulsed field gradients. The relationship between conductivity tensor and eddy currents was derived based on Maxwell’s equations. Simulation, phantom and in vivo brain experiments were conducted to demonstrate that tissue conductivity is measurable by pulsed gradients using standard MRI equipments. By changing gradient orientations, different components of the conductivity tensor can also be assessed. This method provides a new means for MRI to image tissue conductivity and conductivity anisotropy in vivo and non-invasively.

Stefano Mandija¹, Astrid L.H.M.W. van Lier¹, Axel Thielscher^2,3, Andre Antunes⁴, Sebastiaan F.W. Neggers⁵, Peter R. Luijten¹, and Cornelis A.T. van den Berg^1
1Imaging Division, University Medical Center, Utrecht, Netherlands, ²Danish Research Centre for Magnetic Resonance, Copenhagen, Denmark,³Technical University of Denmark, Kgs. Lyngby, Denmark, ⁴Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ⁵Rudolf Magnus Institute of Neuroscience, University Medical Center, Utrecht, Netherlands

At low frequency (Hz-kHz) the human body is electrically very heterogeneous. Adjacent biological structures constitute strong electrical impedance variations that affect current flow. In this work, we studied the effect of electrical impedance variations on the magnetic field distortions by inducing eddy currents caused by the readout gradient. We performed simulations and measurements on saline phantoms. We saw that, by measuring the induced Bz field, it is possible to derive information about the electric conduction and composition of media, e.g. interfaces and their orientation.

Hyunyeol Lee¹, Chul-Ho Sohn², Woo Chul Jeong³, Hyung Joong Kim³, Eung Je Woo³, and Jaeseok Park^1
1Brain and Cognitive Engineering, Korea University, Seoul, Korea, ²Seoul National University Hospital, Seoul, Korea, ³Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi, Korea

In this work, we develop a novel, current-controlled, alternating steady state free precession imaging for rapid biological tissue conductivity mapping. As compared with conventional conductivity mapping technique, the proposed method provides high imaging efficiency without apparent loss of accuracy.

Seung-Kyun Lee¹, Selaka Bandara Bulumulla¹, and Ileana Hancu^1
1GE Global Research, Niskayuna, NY, United States

Tissue electrical properties (TEP) can be calculated from RF-induced complex image intensity variation in standard MR images. Whereas conventional B1 map-based TEP mapping relies on a transmit/receive birdcage coil, the image-based method allows use of multichannel receiver arrays for higher SNR. Here we demonstrate the principle of image-based TEP mapping with a multi-channel receiver array with optimized phase weighting.