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Safoura Sadegh Pour Aji Bishe^1,2, Kay Pepin^1,2, Jeremiah Heilman^1,2, Xiang Shan¹, Ziying Yin¹, and Richard Ehman^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²Resoundant, Inc., Rochester, MN, United States

Keywords: Safety, Brain, Elastography

Magnetic resonance elastography (MRE) requires application of mechanical vibrations to assess the stiffness of tissue noninvasively and quantitatively. This study assessed the levels of vibration exposure in brain tissue during a typical brain MRE exams performed for clinical research. Voxel-level vibration exposure levels throughout the brain were measured in 45 subjects in this IRB approved study.  Histograms of voxel-level vibration in all cases demonstrated maximum exposure levels that were well below the very conservative EU 2002 Directive 2002/44/EC of the European Parliament guideline for total body vibration.

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Helge Herthum¹, Rafaela V. Silva², Anna S. Morr³, Mehrgan Shahryari³, Matthias Anders³, Yasmine Safraou³, Stefan Hetzer¹, Jürgen Braun³, Michael Scheel⁴, Friedemann Paul⁴, Carmen Infante-Duarte², and Ingolf Sack^3
1Berlin Center for Advanced Neuroimaging, Charité Universitätsmedizin Berlin, Berlin, Germany, ²Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany, ³Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany, ⁴Department of Neuroradiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany

Keywords: Elastography, Brain, Cortical stiffness

Multiple sclerosis (MS) is a chronic neuroinflammatory disease that affects both white matter and cortical areas. While magnetic resonance imaging (MRI) can image pathological changes in the white matter, it is limited in quantifying cortical tissue damage in MS. Therefore, cerebral 3D-MR elastography based on multifrequency wave excitation and tomoelastography postprocessing was developed to measure cortical stiffness. We found that the cerebral cortex in MS patients is markedly softer than global brain matter and deep gray matter indicating the use of cerebral tomoelastography as a potential new imaging marker for monitoring MS disability.

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Siri Fløgstad Svensson^1,2, Oliver Geier¹, Elies Fuster-Garcia^1,3, Gunnhild Ager-Wick¹, Robin Anthony Birkeland Bugge¹, Anne-Hilde Farstad⁴, Karoline Skogen⁵, and Kyrre Eeg Emblem^1
1Department for Physics and Computational Radiology, Oslo University Hospital, Oslo, Norway, ²Department for Physics, University of Oslo, Oslo, Norway, ³Universitat Politècnica de València, BDSLab, Instituto Universitario de Tecnologías de la Información y Comunicaciones, València, Spain, ⁴Department for Radiography, Oslo University Hospital, Oslo, Norway, ⁵Department for Radiology, Oslo University Hospital, Oslo, Norway

Keywords: Elastography, Elastography

A previous study in the liver suggested that DWI can be used for virtual elastography. Here, we investigate the potential correlations between DWI-derived parameters and MR elastography (MRE) stiffness measurements in sixteen patients with brain cancer. The highest cross-correlation was obtained between stiffness and the shifted ADC map with b-values 1000 and 3000 s/mm² (median cross correlation 0.91). However, no correlation between mean values of MRE and sADC_1000,3000 was found in normal-appearing white and gray matter, nor in tumor regions. This could be due to a too simple diffusion model and the anisotropic tissue structure of the brain.

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Dhrubo Jyoti¹, Diego Caban-Rivera², Mary Kramer², Alexa Diano², Curtis Johnson², Elijah Van Houten³, Keith Paulsen¹, and Matthew Mcgarry^1
1Dartmouth College, Hanover, NH, United States, ²University of Delaware, Newark, DE, United States, ³University of Sherbrooke, Sherbrooke, QC, Canada

Keywords: Elastography, In Silico

Simulations can play an important role in validating the accuracy of MR elastography (MRE) inversion algorithms. A realistic brain MRE simulation is created through a finite element model from in vivo MRE data, with 20 randomly generated simulated brains created by assigning properties of anatomical segmentations of brain structures within a range given by a published MRE atlas. Multi-frequency and multi-direction synthetic MRE data was generated via boundary conditions from in vivo measured motions to allow a range of inversion algorithms to be tested. These data will be supplied to the MRE study group for an inversion reconstruction challenge.

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Harish Palnitkar¹, Matthew C Murphy¹, Yi Sui¹, Kevin J Glaser¹, Armando Manduca¹, John Huston 3rd¹, Richard L Ehman¹, and Arvin Arani^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States

Keywords: Elastography, Elastography, Functional MR Elastography

The response of BOLD fMRI to changes in both visual contrast frequency and contrast intensity have been well documented. Recently, an increase in the stiffness of activated regions of the visual cortex due to a controlled variation of block duration has been demonstrated with fMRE elastograms. The current study aims to investigate the relationship between BOLD fMRI and fMRE due to a controlled variation of both contrast intensity and contrast frequency of a visual stimulation. This study demonstrates that the fMRE-measured stiffness change varies linearly with the underlying neural activity, which can be modulated by stimulus parameterization.

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Emily Triolo¹, Mackenzie Langan^2,3, Oleksandr Khegai², Akbar Alipour², Carolina Ferreira-Atuesta³, Aymeric Pionteck¹, Jonathan Sutkowski³, Trey Hedden³, Priti Balchandani², and Mehmet Kurt^1,2
1Mechanical Engineering, University of Washington, Seattle, WA, United States, ²Biomedical Engineering and Imaging Institute, Ichan School of Medicine at Mount Sinai, New York City, NY, United States, ³Graduate School of Biomedical Sciences, Ichan School of Medicine at Mount Sinai, New York City, NY, United States

Keywords: Elastography, Brain, 7T, Alzheimer's Disease, PET

Previous studies have implied the future use of MRE metrics to track disease progression and as a tool for AD diagnosis, potentially replacing or augmenting methods that use ionizing radiation. In this pilot study, we have therefore developed a novel framework for performing ultrahigh field (7T) MRE at high resolution on subjects who have previously undergone PET scans and performing joint analysis of biomechanical and pathologic markers on these subjects. We have successfully created a framework for measurement of high-resolution brain mechanical properties for co-correlation with traditional PET measures to be used on AD patients in the future.

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Shujun Lin¹, Bradley Sutton², Richard Magin¹, Aaron Anderson², and Dieter Klatt^1
1Biomedical Engineering, University of Illinois Chicago, Chicago, IL, United States, ²Beckman Institute, University of Illinois Urbana-Champaign, Urbana, IL, United States

Keywords: Elastography, Elastography

Simultaneous acquisition of diffusion tensor imaging and multifrequency magnetic resonance elastography was examined in this preliminary study on in vivo human brain. The mDTIMRE was achieved by ensuring the same diffusion encoding using experiment parameters with different mechanical frequencies, while fulfilling the timing condition of simultaneous acquisition. By applying a multifrequency dual elasto-visco inversion approach, the effective image resolution of mechanical property maps is improved and enables quantitatively assessment of tissue properties in brain sub-regions. The experiment results show a good correlation between mDTIMRE and conventional measurements.

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Diego A. Caban-Rivera¹, Elijah E. W. Van Houten², Matthew D. J. McGarry³, L. Tyler Williams¹, Phil V. Bayly⁴, Keith D. Paulsen³, and Curtis L. Johnson^1
1Biomedical Engineering, University of Delaware, Newark, DE, United States, ²Département de Génie Mécanique, Université de Sherbrooke, Sherbrooke, QC, Canada, ³Thayer School of Engineering, Dartmouth College, Hanover, NH, United States, ⁴McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, United States

Keywords: Elastography, Brain

This study combined multiexcitation MRE (ME-MRE), and multifrequency MRE (MF-MRE) with a transversely isotropic nonlinear inversion (TINLI) and axonal fiber directions from diffusion tensor imaging to investigate anisotropic and frequency-dependent material properties simultaneously. These preliminary results show that multifrequency-TINLI MRE can be readily applied to in vivo human data at distinct frequencies.

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Olivia M Bailey¹, Alexa M Diano¹, Ali H Lateef¹, Elise A Corbin¹, and Curtis L Johnson^1
1Biomedical Engineering, University of Delaware, Newark, DE, United States

Keywords: Elastography, Traumatic brain injury

This study uses magnetic resonance elastography (MRE) with incremental compression to measure the apparent viscoelastic properties of bovine brain tissue as pre-strain is applied. Results from our tissue-agar phantom showed an increase in stiffness, and a decrease in damping ratio for the bovine brain. The agar showed an increase in stiffness and no consistent change in damping ratio. This research serves as the foundation for future studies measuring the nonlinear properties of human cadaveric brain tissue. Output from this work will be instrumental in advancing current traumatic brain injury (TBI) models.  

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Matthew Mcgarry¹, Damian Sowinski¹, Diego Caban-Rivera², Elijah Van Houten³, Curtis Johnson², Keith Paulsen¹, and Philip Bayly^4
1Dartmouth College, Hanover, NH, United States, ²University of Delaware, Newark, DE, United States, ³University of Sherbrooke, Sherbrooke, QC, Canada, ⁴Washington University in St Louis, St Louis, MO, United States

Keywords: Elastography, White Matter

Anisotropic MRE has shown some promise in estimating mechanical properties of fiber-reinforced biological tissues. However, these methods are restricted to modeling a single fiber and ignores complexity that occurs such as regions of brain white matter with crossing fibers. Here we implement an inversion algorithm capable of modeling material with two fiber directions obtained from diffusion MRI in order to reduce model data mismatch and provide fiber-specific properties, which may show promise in correlating with brain health and function. Performance of this algorithm is demonstrated in simulation and in vivo brain data and compared with one-fiber and zero-fiber (isotropic) inversions.

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Yi Sui¹, Matthew C. Murphy¹, Ziying Yin¹, Kevin J. Glaser¹, Richard L. Ehman¹, Matt A. Bernstein¹, John Huston III¹, and Yunhong Shu^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States

Keywords: Elastography, Brain, MRE, Compact 3T

We conducted a direct comparison of Brain MRE performance between a compact, lightweight 3T scanner (C3T) and a whole-body scanner (WB3T). We demonstrate in phantom and volunteers that the C3T scanner provides superior image quality and scanning efficiency for commonly performed brain MRE pulse sequences, especially for higher-resolution scanning.

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Alex M Cerjanic^1,2, Alexa M Diano², Matthew DJ McGarry³, and Curtis L Johnson^2
1Department of Medicine, Massachusetts General Hospital, Boston, MA, United States, ²Department of Biomedical Engineering, University of Delaware, Newark, DE, United States, ³Dartmouth College, Hanover, NH, United States

Keywords: Elastography, Data Acquisition

This study demonstrates the use of magnetization preparation for MR elastography in combination with a 3D GRE stack of spirals pulse sequence. By decoupling the motion encoding from the readouts, rapid encoding strategies, such as 3D GRE, can be used. MRE images, displacement, and inverted elastograms are obtained on in vivo human brain. 3D GRE readouts with EMPIRE motion encoding can acquire a complete MRE dataset 33% faster than 2D SE-EPI with similar parallel imaging acceleration factors. 

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Rolf Reiter¹, Florian Nino Loch², Carsten Kamphues³, Mehrgan Shahryari¹, Stephan Rodrigo Marticorena Garcia¹, Britta Siegmund⁴, Carl Weidinger⁴, Anja Kühl⁵, Bernd Hamm¹, Jürgen Braun⁶, Ingolf Sack¹, Patrick Asbach¹, and Laura Jensen^1
1Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, ²Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany, ³Surgery, Parkklinik Weißensee, Berlin, Germany, ⁴Gastroenterology, Infectious Diseases and Rheumatology, Charité - Universitätsmedizin Berlin, Berlin, Germany, ⁵iPATH.Berlin-Immunopathology for Experimental Models, Charité - Universitätsmedizin Berlin, Berlin, Germany, ⁶Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany

Keywords: Elastography, Body, inflammatory bowel disease

Despite increasing evidence that the functional involvement and structural changes of mesenteric adipose tissue influence the course of Crohn's disease, its viscoelastic properties remain elusive. We demonstrate the feasibility of in vivo MR elastography of mesenteric adipose tissue and present preliminary reference values for Crohn's disease patients and healthy controls in this explorative study. Our preliminary results show an excellent diagnostic performance in detecting Crohn's disease by assessing the viscoelastic properties of mesenteric adipose tissue using histopathology of surgical specimens as reference. Our results motivate further studies for the biophysical characterization of mesenteric adipose tissue in inflammatory bowel disease.

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Amirhosein Baradaran Najar^1,2, Elige Karam^2,3, Guillaume Gilbert⁴, Maxime Barat^2,3, Emmanuel Montagnon³, Hélène Castel⁵, Jeanne-Marie Giard⁵, Bich Nguyen⁶, Guy Cloutier^2,7,8, An Tang^2,7, and Elijah Van Houten^1,9
1Département du génie mécanique, Université de Sherbrooke, Sherbrooke, QC, Canada, ²Centre de recherche du Centre hospitalier de l'Université de Montréal (CRCHUM), Montréal, QC, Canada, ³Department of Radiology, Radiation Oncology and Nuclear Medicine, Université de Montréal, Montréal, QC, Canada, ⁴Philips Healthcare, Mississauga, ON, Canada, ⁵Centre Hospitalier de l’Université de Montréal (CHUM), Montréal, QC, Canada, ⁶Service of Pathology, Centre Hospitalier de l’Université de Montréal (CHUM), Montréal, QC, Canada, ⁷Institute of Biomedical Engineering, Université de Montréal, Montréal, QC, Canada, ⁸Laboratory of Biorheology and Medical Ultrasonics(LBUM), Centre de recherche du Centre hospitalier de l’Université de Montréal (CRCHUM), Montréal, QC, Canada, ⁹Centre de recherche du Centre hospitalier de l'Université de Sherbrooke (CRCHUS), Sherbrooke, QC, Canada

Keywords: Elastography, Elastography, Intrinsic magnetic resonance elastography, Cancer

Intrinsic activation MR elastography (iMRE) method has been applied to a cohort of patients undergoing liver MRI for assessment of focal liver lesions. We used segmentation, masking, and normalization of viscoelastic parameters to investigate the capability of this method to differentiate benign and malignant liver lesions. The normalized storage modulus (G') computed by nonlinear inversion-iMRE showed significant differences between benign and malignant lesions.

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Rolf Reiter^1,2, Harish Palnitkar³, Shreyan Majumdar⁴, Joseph Crutison⁴, Shujun Lin⁴, Thomas J. Royston⁴, and Dieter Klatt^4
1Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany, ²BIH Biomedical Innovation Academy, BIH Charité Digital Clinician Scientist Program, Berlin Institute of Health at Charité – Universitätsmedizin Berlin, Berlin, Germany, ³Radiology, Mayo Clinic, Rochester, MN, United States, ⁴Richard and Loan Hill Department of Biomedical Engineering, University of Illinois Chicago, Chicago, IL, United States

Keywords: Elastography, Tissue Characterization

The recently developed 1-Norm technique can be used to quantify the extend of scattering of mechanical waves generated by inhomogeneities. This explorative study shows that 1-Norm can detect mechanical inhomogeneity of ex vivo kidney, liver and muscle without the need to use ill-posed wave inversion techniques. The 1-Norm technique has potential to serve as an MRE-based diagnostic biomarker independent of stiffness for the characterization of pathological conditions associated with changes in tissue mechanical inhomogeneity.

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Anne-Sophie van Schelt^1,2, Nienke Petronella Maria Wassenaar¹, Jurgen H. Runge¹, Jaap Stoker^1,2,3, Aart J Nederveen¹, and Eric M Schrauben^1
1Radiology and Nuclear Medicine, Amsterdam UMC, location AMC, Amsterdam, Netherlands, ²Imaging and Biomarkers, Cancer Center Amsterdam, Amsterdam, Netherlands, ³Endocrinology, Metabolism, Amsterdam Gastroenterology, Amsterdam, Netherlands

Keywords: Elastography, Pancreas

Breathing motion can be detrimental to quantitative accuracy in pancreatic MR elastography (MRE). We investigated motion-correction strategies on sagittal multi-frequency free-breathing SE-EPI MRE acquisitions to mitigate breathing-motion and increase accuracy. Breathing-states were determined through a respiratory-belt and multiple number of bins were tested. Three intensity-based registration methods (with and without non-rigid post-processing) and non-rigid registration were ranked on MRE quality measures. The best method showed improved data quality, inversion precision and repeatability compared to no correction, but resulted in apparently increased shear wave speed (SWS), which warrants further investigation.

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Matthias Anders¹, Carsten Warmuth¹, Josef Pfeuffer², Heiko Tzschätzsch¹, Helge Herthum¹, Katja Degenhardt³, Oliver Wieben⁴, Sebastian Schmitter³, Jeanette Schulz-Menger^1,5,6, Jürgen Braun¹, and Ingolf Sack^1
1Charité - Universitätsmedizin Berlin, Berlin, Germany, ²MR Application Development, Siemens Healthcare, Erlangen, Germany, ³Physikalisch-Technische Bundesanstalt(PTB), Braunschweig and Berlin, Berlin, Germany, ⁴University of Wisconsin, Madison, WI, United States, ⁵Experimental and Clinical Research Center (ECRC), DZHK partner site Berlin, Berlin, Germany, ⁶HELIOS Klinikum Berlin Buch, Berlin, Germany

Keywords: Elastography, Data Acquisition

MR elastography (MRE) can noninvasively detect liver fibrosis based on elevated stiffness values. However, a complete MRE scan is time-consuming and typically extends over multiple breath-holds. Therefore, a multi-shot gradient echo sequence with spiral readout was developed to provide full two-dimensional elastograms of the liver in less than one second. The new sequence can be used as an MRE navigator to provide immediate feedback on wave penetration and data consistency for parameter optimization prior to running full multi-dimensional MRE. Moreover, the method can be used to rapidly track potential changes in liver stiffness such as those induced by respiration.

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Nienke P.M. Wassenaar^1,2, Anne-Sophie van Schelt^1,2, Eric M. Schrauben¹, Hanneke W.M. van Laarhoven^2,3, Jaap Stoker^1,2, Aart J. Nederveen¹, and Jurgen H. Runge^1
1Radiology and Nuclear Medicine, Amsterdam University Medical Centers, Amsterdam, Netherlands, ²Imaging and Biomarkers, Cancer Center Amsterdam, Amsterdam, Netherlands, ³Medical Oncology, Amsterdam University Medical Centers, Amsterdam, Netherlands

Keywords: Elastography, Pancreas

MR elastography (MRE) could be useful as an imaging biomarker in pancreatic cancer. To this end, pancreatic MRE parameters should be repeatable and be able to differentiate between healthy and tumour tissue. In this study, 10 patients with pancreatic ductal adenocarcinoma and 8 sex- and age-matched healthy volunteers underwent three MRE scans in a test-retest set-up. Results showed that MRE parameters were repeatable in patients and healthy volunteers. Furthermore, a significant increase in shear wave speed was found in pancreatic tumours compared to healthy pancreatic tissue.

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Yuan Le¹, Jun Chen¹, Phillip J. Rossman¹, Armando Manduca¹, Kevin J. Glaser¹, Bradley D. Bolster Jr.², Stephan Kannengiesser³, and Richard L. Ehman^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²US MR R&D Collaboration, Siemens Medical Solutions Inc., Salt Lake City, UT, United States, ³MR Application Predevelopment, Siemens Healthcare GmbH, Erlangen, Germany

Keywords: Elastography, Elastography, Transient wave, multi-scale encoding

We demonstrate imaging of the propagation of transient waves using multi-scale motion encoding gradient waveforms. Displacement values are calculated using the inverse Haar transforms. We validated the results by comparison with wave images obtained using standard MRE acquisition and processing. The approach provides the ability to image broadband motion more efficiently and accurately compared with previous methods and promises to be a useful approach for biomechanical studies of traumatic brain injury.

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Emily Triolo¹, Melih Eriten², Curtis Johnson³, and Mehmet Kurt^1,4
1Mechanical Engineering, University of Washington, Seattle, WA, United States, ²Mechanical Engineering, University of Wisconsin–Madison, Madison, WI, United States, ³Biomedical Engineering, University of Delaware, Newark, DE, United States, ⁴Biomedical Engineering and Imaging Institute, Ichan School of Medicine at Mount Sinai, New York City, NY, United States

Keywords: Elastography, Phantoms, Wave Propagation, Biointerface

While MRE can be used to calculate mechanical properties of tissue, bio-interfaces can cause distortions in the shear-wave propagation patterns which are difficult to account for with current MRE techniques. Therefore, we utilized three specialized MRE sequences to visualize the first three harmonics of wave propagation in phantoms with simulated bio-interfaces. We were able to measure the doubling and tripling of wave number in the phantoms excited at the fundamental vibration frequency using this optimized MRE protocol. We characterized differences in wave propagation at higher harmonics along phantom interfaces, and observed substantial differences in wave characteristics based on adhesion level.