Translational Scientific Session: Susceptibility Image in the Brain

Monday 22 April 2013

Wei Li¹, Hui Han¹, Arnaud Guidon¹, and Chunlei Liu^1,2
1Brain Imaging & Analysis Center, Duke University, Durham, North Carolina, United States, ²Radiology, Duke University, Durham, North Carolina, United States

Phase images of gradient-recalled echo (GRE) have provided a new contrast for MRI. It is well known that the magnitude contrast of GRE signal changes as a function of sequence parameters including TR, TE and flip angle. The dependence of phase contrast on these parameters, however, has not been explored. In fact, phase contrast has largely been assumed in the literature to be insensitive to sequence parameters. We show that phase contrast has a profound dependence on sequence parameters that can be described by a multi-compartment model. This dependence may provide further insights of the mechanisms of susceptibility contrast.

Maged Goubran¹, Brendan Santyr¹, Dave A. Rudko¹, Joseph S. Gati¹, Trevor Szekeres¹, Terry M. Peters¹, and Ali R. Khan^1
1Robarts Research Institute, London, Ontario, Canada

The hippocampus and its substructures are of great importance in the pre-operative evaluation of intractable epilepsy. Quantitative MRI sequences have the added benefit of providing additional information, such as T2* relaxation time and quantitative volume magnetic susceptibility of hippocampal substructures. This work focuses on the construction of a normative atlas of the hippocampal subfields from in vivo susceptibility weighted images of eighteen healthy volunteers on 7T MRI. Using a reliable manual delineation protocol of the subfields, we demonstrated the feasibility of using our atlas in voxel based and morphometry analysis of the hippocampus.

Assunta Dal-Bianco¹, Günther Grabner², Hans Lassmann³, Melanie Schernthaner⁴, Claudia Kronnerwetter⁵, Michael Weber⁴, Clemens Vass⁶, Karl Kircher⁶, Andreas Reitner⁶, Eduard Auff⁷, and Siegfried Trattnig^5
1Department of Neurology, Medical University of Vienna, Vienna, Austria, ²High field MR Center of Excellence, Department of Radiology, Medical University of Vienna, Vienna, Austria, ³Center for Brain Research, Medical University of Vienna/Vienna General Hospital, Vienna, Austria, ⁴Department of Radiology, Medical University of Vienna/Vienna General Hospital, Vienna, Austria, ⁵High field MR Center of Excellence, Department of Radiology, Medical University of Vienna/Vienna General Hospital, Vienna, Austria, ⁶Department of Ophthalmology and Optometrics, Medical University of Vienna/Vienna General Hospital, Vienna, Austria,⁷Department of Neurology, Medical University of Vienna/Vienna General Hospital, Vienna, Austria

Intralesional veins are known to be a histopathological hallmark of Multiple Sclerosis. Inflammatory tissue of relapsing-remitting and secondary-progressive multiple sclerosis plaques show a significantly higher proportion of deoxygenated veins compared to corresponding non-inflammatory control tissue and corresponding normal appearing white matter tissue. Proportion of visible veins within plaques did not change significantly within 2 years. Ultrahigh spatial resolution provided by the high SNR and the higher phase shift at 7T allows to analyze vein density in MS plaques in comparison to normal appearing white matter which may provide an insight into the pathophysioloy of MS in vivo.

Sung Suk Oh^1,2, Se-Hong Oh¹, HyunWook Park², and Jongho Lee^1
1Department of Radiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States, ²Department of Electrical Engineering, KAIST, Daejeon, Korea

We propose a novel method to remove image artifacts in susceptibility weighted imaging. The resulting image show no artifacts in orbitofrontal and temporal lobes.

Bo Xu^1,2, Tian Liu², Pascal Spincemaille², and Yi Wang^1,2
1Biomedical Engineering, Cornell University, Ithaca, New York, United States, ²Weill Cornell Medical College, New York, New York, United States

Flow artifacts in quantitative susceptibility mapping (QSM) are corrected with a fully flow compensated multi-echo gradient echo sequence combined with a hybrid linear-quadratic fitting of the phase data. Phantom experiments and in vivo studies demonstrate improvements in the estimation of the field inhomogeneity and the susceptibility map. This enables more reliable venous oxygenation quantification in the brain with QSM.

Jaladhar Neelavali¹, Haacke Mark Ewart¹, Swati Mody¹, Lami Yeo^2,3, Sheena Saleem⁴, Yashwanth Katkuri¹, Pavan Jella⁵, Ray O. Bahado-Singh³, Sonia Hassan^2,3, Robert Romero², and Moriah Thomason^4,6
1Department of Radiology, Wayne State University, Detroit, MI, United States, ²Perinatology Research Branch,NICHD, NIH, DHHS, Detroit, MI, United States,³Department of Obstetrics and Gynecology, Wayne State University, Detroit, MI, United States, ⁴Department of Pediatrics, Wayne State University, Detroit, MI, United States, ⁵Biomedical Engineering, Wayne State University, Detroit, MI, United States, ⁶Perinatology Research Branch, Wayne State University, Detroit, MI, United States

Demonstrating the feasibility of performing fetal cerebral venography using SWI at different gestation ages.

Alexander Radbruch^1,2, Johanna Mucke¹, Matthias Roethke², Heinz-Peter Schlemmer², Sabine Heiland¹, Martin Bendszus¹, and Stefan Rohde^1
1Department of Neuroradiology, Heidelberg University Medical Center, Heidelberg, Germany, ²Department of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany

While time of flight (TOF) angiography detects occlusion of arteries in patients with acute ischemic stroke due to the absence of blood flow in the occluded vessel, Susceptibility Weighted Imaging (SWI) enables visualization of the occluding thrombus. In our study we investigated the sensitivity of both methods for the detection of peripheral and central vessel occlusion and found SWI to be superior to TOF-angiography for the detection of peripheral thrombi.

Berkin Bilgic¹, Itthi Chatnuntawech¹, Audrey Peiwen Fan¹, and Elfar Adalsteinsson^2,3
1EECS, Massachusetts Institute of Technology, Cambridge, MA, United States, ²EECS, MIT, Cambridge, MA, United States, ³Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA, United States

Regularized Quantitative Susceptibility Mapping reconstruction with computation time on the order of seconds is demonstrated by expressing the solution of the associated optimization problem in closed-form. In place of iterative algorithms, this simple and fast reconstruction technique can enable online computation of susceptibility maps on the scan site.

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

A new phase/field artifact removal method is introduced that is based on the SHARP (“Sophisticated Harmonic Artifact Reduction for Phase data”) method exploiting the harmonic mean value property. This new method employs Tikhonov regularization at the deconvolution stage of the mean value implementation, and is referred to as Regularization Enabled SHARP (RESHARP). RESHARP was compared to SHARP in a field-forward susceptibility simulation and in human brain experiments, demonstrating that it removes background field artifact more effectively compared to SHARP, leading to susceptibility maps with fewer artifacts and more accurate susceptibility measurement in deep grey matter structures.

Ludovic De Rochefort¹, Hongchen Wang², Paulo Loureiro de Sousa³, and Jean-Paul Armspach^3
1Univ Paris-Sud, Orsay, France, ²Univ. Paris Sud - CNRS, UMR 8081, IR4M, Orsay, France, ³Université de Strasbourg, CNRS, ICube (UMR 7357), FMTS, Strasbourg, France

a full processing of multi-echo gradient-echo data brain is described to efficiently extract the field inhomogeneities inside the brain while removing background effects. First, phase maps including background effect are unwrapped in time using a fast Fourier transform, and then fitted to an affine model to estimate the field. A T1-weigthed scan is then used to segment the brain. Internal field within the brain is finally efficiently extracted using harmonic filtering, i.e. by solving Laplace equation with adequate boundary conditions. Field wrapping in space is removed in the process using the modulo function. Internal field and QSM obtained in vivo at 3T are presented, and compared to R1 (=1/T1) and R2* = (1/T2*) maps.