Magnetic Susceptibility: Towards Clinical Application

Thursday 15 May 2014

Vanessa Wiggermann^1,2, Enedino Hernández Torres^1,3, Irene M. Vavasour^1,3, Alex L. MacKay^2,3, David K.B. Li^1,3, Anthony Traboulsee^3,4, and Alexander Rauscher^1,3
1Radiology, University of British Columbia, Vancouver, BC, Canada, ²Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada,³UBC MRI Research Centre, Vancouver, BC, Canada, ⁴Neurology, University of British Columbia, Vancouver, BC, Canada

Long-term changes in multiple sclerosis (MS) patients are often monitored measuring lesion load and observing changes in size and shape of MS lesions. However, high-spatial resolution tools for the estimation of quantitative changes in MS lesions are still missing. Here, we exploit MR frequency shift imaging as a high-resolution tool to monitor long-term changes in MS lesions. Frequency mapping showed great sensitivity to changes at lesion appearance and at long-term follow up of the same lesions, 3-5 years after appearance.

Cynthia Wisnieff¹, Alexey Dimov^1,2, David Pitt³, 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

This preliminary data explores changes in the susceptibility (STI) and relaxation tensor (R2*T) properties of multiple sclerosis (MS) lesions in MRI as a result of structural changes that occur as a result of demyelinating process that occurs within these lesions. Ex vivo brain specimens were examined in an unconstrained susceptibility and relaxation tensor reconstruction to explore changes in the anisotropy, alignment and mean tensor properties were examined. This works shows significant loss of alignment within lesions while major white matter tracts retain significant alignment and anisotropy.

Vanessa Wiggermann^1,2, Lisa E. Lee³, Enedino Hernández Torres^1,4, David K.B. Li^1,4, Alex L. MacKay^2,4, Irene M. Vavasour^1,4, Anthony Traboulsee^4,5, 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, ⁵Neurology, University of British Columbia, Vancouver, BC, Canada

The contrast observed in MR frequency shift imaging in multiple sclerosis (MS) lesions has been attributed to iron. However, histopathology studies indicated that iron is a rather rare feature and mainly found in the rim of some lesions. Iron would create non-local distortions of the magnetic field outside susceptibility inclusions. For spheres, the non-local field effect results in a dipole (reduced frequency around the equator of the inclusion and increased frequency in the direction of the magnetic field). We inspected 37 enhancing and 90 non-enhancing nearly spherical lesions. Only 4% of these lesions showed the described feature.

Xu Li^1,2, Hongjun Liu^1,3, Daniel M Harrison⁴, Craig K Jones^1,2, Jiwon Oh⁴, Peter A Calabresi⁴, and Peter C.M. van Zijl^1,2
1F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States, ²Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, ³Radiology, Guangdong General Hospital, Guangzhou, Guangdong, China, ⁴Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States

White matter magnetic susceptibility contrasts in MS were investigated using gradient echo magnitude, R2*, frequency, and quantitative susceptibility mapping (QSM). For QSM, both hyperintense (increased susceptibility) and isointense lesions were observed. A larger proportion (88.3%) of periventricular lesions were hyperintense, while a larger proportion (74.6%) of subcortical lesions were isointense. Increased lesion susceptibility may indicate either iron deposition or demyelination, while decreased R2* suggests myelin loss or low iron concentration. All R2* lesions appeared darker than normal white matter and all susceptibility lesions brighter or isointense, suggesting myelin loss as the dominant pathologic mechanism accounting for the observed findings.

Clare B Poynton¹, Janine M Lupo¹, Christopher P Hess¹, and Sarah J Nelson^1,2
1Department of Radiology and Biomedical Imaging, University of California, San Francisco, CA, United States, ²Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, United States

Quantifying iron deposition in Huntington’s disease and other neurodegenerative disorders may provide insight into disease pathogenesis, aid in patient diagnosis or evaluating response to treatment. Iron accumulation changes the tissue magnetic susceptibility, which can be quantified from the MR signal phase using quantitative susceptibility mapping (QSM). In this study, we apply the QSIP algorithm to quantify magnetic susceptibility in premotor Huntington’s patients imaged at 7 Tesla. Results show statistically significant increases in QSM estimates in the caudate, putamen and globus pallidus relative to controls, which is consistent with hypothesized disease-related iron deposition in these regions.

Deqiang Qiu¹, R Clark Brown^2,3, Binjian Sun⁴, Susan Palasis⁴, Thomas G Burns⁵, and Richard A Jones^1,4
1Radiology, Emory University, Atlanta, GA, United States, ²Haematology, Children's Healthcare of Atlanta, Atlanta, GA, United States, ³Haematology, Emory University, Atlanta, GA, United States, ⁴Radiology, Children's Healthcare of Atlanta, Atlanta, GA, United States, ⁵Neuropsychology, Children's Healthcare of Atlanta, Atlanta, GA, United States

Pediatric sickle cell disease patients with high cerebral blood flow receiving chronic blood transfusion to reduce the risk of stroke. Quantitative susceptibility mapping was used to study the brain iron levels in these patients compared to a group of healthy control subjects. Significant higher susceptibility values were found in the patients in multiple brain regions including the choroid plexus, red nucleus and dentate nucleus. QSM is a sensitive tool for monitoring brain iron level and allows customized treatment strategy for patients with altered iron level.

Hongfu Sun¹, Vedashree V. Divekar¹, Mahesh Kate², Laura C. Gioia², Corey A. Baron¹, Christian Beaulieu¹, Derek J. Emery³, Ken Butcher², and Alan H. Wilman^1
1Biomedical Engineering, University of Alberta, Edmonton, AB, Canada, ²Neurology, University of Alberta, AB, Canada, ³Radiology, U of Alberta, AB, Canada

We studied the potential of Quantitative Susceptibility Mapping in intracranial hemorrhage in comparison to standard MRI and x-ray CT in 9 patients and using a numerical simulation.

Julio Acosta-Cabronero¹, Guy B Williams², Arturo Cardenas-Blanco¹, and Peter J Nestor^1
1Brainplasticity & Neurodegeneration, German Center for Neurodegenerative Diseases (DZNE), Magdeburg, Saxony-Anhalt, Germany, ²Wolfson Brain Imaging Centre, University of Cambridge, Cambridge, Cambridgeshire, United Kingdom

This study explores the magnetostatic properties of the Alzheimer’s disease (AD) brain using quantitative susceptibility mapping (QSM) – a post-processed MRI contrast that has the potential to monitor in vivo iron levels by reconstructing magnetic susceptibility sources from field perturbations. The regional and whole-brain cross-sectional comparisons between AD subjects and matched controls indicate that there may be significant magnetic susceptibility differences for deep brain nuclei – particularly the putamen – as well as for posterior grey and white matter regions. In addition, the methodology and findings described suggest that the QSM method is ready for larger-scale clinical studies.

Wei Li^1,2, Justin Long¹, Lora Talley Watts¹, Qiang Shen¹, and Timothy Q Duong^1,2
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States, ²Ophthalmology, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States

The white matter damage and its related alterations in brain structural connectivity can be an important factor in determining the neurobehavioral outcomes after traumatic brain injury. This study explored the use of magnetic susceptibility, a novel contrast determined from gradient echo signal phase, for the characterization of white matter changes following mild TBI using a rat model. We found that magnetic susceptibility imaging offers improved sensitivity to white matter changes compared to DTI FA. This study showed the potential of magnetic susceptibility for sensitive detection of white matter damages in vivo.

Wei Cao^1,2, Wei Li¹, Hui Han¹, Shonagh K O¡¯Leary-Moore³, Kathleen K Sulik³, G. Allan Johnson⁴, and Chunlei Liu^1,5
1Brain Imaging and Analysis Center, Duke University, Durham, NC, United States, ²Tongji Hospital,Huazhong University of Science and Technology, Wuhan, Hubei, China, ³Bowles Center for Alcohol Studies, University of North Carolina, Chapel Hill, NC, United States, ⁴Center for In Vivo Microscopy, Duke University, Durham, NC, United States, ⁵Department of Radiology, Duke University, Durham, NC, United States

Prenatal alcohol exposure can result in the cognitive and behavioral deficits. Quantitative susceptibility mapping (QSM) and DTI was used to assess its impact to deep white matter in mouse brains, respectively. Two groups of mice (n=7, postnatal day 45) were characterized: an ethanol group and a control group. Three main white matter fibers were analyzed. Significantly decreased susceptibility contrast between gray and white matter in ethanol group in each ROI was observed; and there is no significant difference for FA between the two groups. The result indicates the further application of QSM to brain is very promising.