Helge Herthum¹, Mehrgan Shahryari¹, Gergely Bertalan¹, Carsten Warmuth¹, Stefan Hetzer², Jürgen Braun³, and Ingolf Sack^1
1Department of Radiology, Charité Universitätsmedizin Berlin, Berlin, Germany, ²Bernstein Center for Computational Neuroscience, Berlin, Germany, ³Institute of Medical Informatics, Berlin, Germany

Real-time MR elastography (rt-MRE) with 4.9Hz-frame rate was developed for in-vivo brain stiffness quantification during short-term tissue mechanical adaptation due to cerebral autoregulation. Six healthy participants performed a 15s-Valsalva maneuver with 50s recovery period following 10s resting period and 5s deep inspiration during continuous rt-MRE. 387 maps of tissue stiffness and fluidity were generated depicting a significant increase of stiffness due to Valsalva and an overshoot of stiffness by 3.4% fading out within 7s after the maneuver. rt-MRE is potentially sensitive to several diseases associated with cerebral autoregulation and reveals new insights into brain viscoelasticity changes on short time scales.

Xi Peng¹, Yi Sui¹, Sandeep Ganji², Ashley Anderson², John Huston¹, Richard Ehman¹, and James Pipe^1
1Department of Radiology, Mayo Clinic, Rochester, MN, United States, ²Philips Healthcare, Gainesville, FL, United States

This work reports a new method for fast whole-brain MRE using a 3D gradient-echo multishot variable-density spiral staircase acquisition. The proposed method enables high-resolution MRE by exploiting the inherently improved through-plane parallel imaging. The displacement-SNR is further enhanced by exploiting a motion encoding gradient of a 2 wave-period duration. Constrained reconstruction and deblurring method are used to generate high-quality spiral images. By integrating all these features, the proposed technique provides flexible trade-off among SNR, resolution, spatial blurring and scan time. In vivo experiments have demonstrated the capability of the proposed method for high-SNR high-resolution MRE in less than 5 minutes.

Matthew Mcgarry¹, Elijah Van Houten², Damian Sowinski¹, Philip Bayly³, Daniel Smith⁴, Curtis Johnson⁴, John Weaver^1,5, and Keith Paulsen^1,5
1Dartmouth College, Hanover, NH, United States, ²Université de Sherbrooke, Sherbrooke, QC, Canada, ³Washington University in St Louis, St Louis, MO, United States, ⁴University of Delaware, Newark, DE, United States, ⁵Dartmouth-Hitchcock Medical Center, Lebanon, NH, United States

An implementation of a transverse isotropic model with fiber directions defined by DTI was added to our finite element model-based nonlinear inversion MRE platform. The algorithm can recover accurate images of complex valued shear modulus, shear anisotropy, and tensile anisotropy from a realistic brain simulation. In vivo application to multi-excitation brain MRE data produced promising results, maintaining high quality images for the base shear modulus and damping ratio, while recovering additional images of anisotropy which may be useful for characterizing diseases affecting white matter tracts or muscle.  

Nicolas R Gallo¹, Stacey M Cahoon¹, Aaron T Anderson², Noel M Naughton³, Assimina A Pelegri⁴, and John G Georgiadis^1
1Biomedical Engineering, Illinois Institute of Technology, Chicago, IL, United States, ²Beckman Institute, Urbana, IL, United States, ³Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, United States, ⁴Department of Mechanical and Aerospace Engineering, Rutgers University, New Brunswick, NJ, United States

Healthy aging involves local variations in viscoelastic shear properties of the brain. We employ high-resolution, multi-excitation MRE and a novel anisotropic inversion scheme (iTI) to extract local shear anisotropic moduli in vivo. The ratio of transverse to axial moduli, a new MRE metric, remains greater than 1 along the splenium, body and genu regions of the corpus callosum for both young and old subjects. This metric peaks in the body region and decreases with age throughout the corpus callosum.

Shan Pi¹, Jonathan M. Scott², Yin Li³, Hui Peng³, Huiquan Wen¹, Matthew C. Murphy², Jingbiao Chen¹, Meng Yin², Jun Chen², Kevin J. Glaser², Rchard L. Ehman², and Jin Wang^1
1Department of Radiology, the Third Affiliated Hospital, Sun Yat-sen University, Guang Zhou, China, ²Department of Radiology, Mayo Clinic, Rochester, Micronesia, ³Department of Nephrology, the Third Affiliated Hospital, Sun Yat-sen University, Guang Zhou, China

Chronic kidney disease (CKD) is increasing in incidence and prevalence worldwide and early detection of CKD is a major challenge. MR elastography (MRE) is a noninvasive technique capable of quantifying the mechanical properties of tissue that has shown potential for assessing kidney diseases. MRE using 60-Hz and 90-Hz vibration frequencies can provide potential quantitative biomarkers for evaluating kidney function and biopsy score in CKD patients.

Gwenaël Pagé¹, Laurent Besret², Marion Tardieu¹, Maïlys Vidal¹, Bernard Van Beers^1,3, and Philippe Garteiser^1
1Laboratory of Biomarkers in Imaging, Center of Research on Inflammation, UMR 1149 Inserm-Université de Paris, Paris, France, ²Sanofi R&D, Vitry-sur-Seine, France, ³Department of Radiology, Beaujon University Hospital Paris Nord, Clichy, France

The purpose of this study was to assess in two different human liver tumours the correlation between tumour solid stress and changes of mechanical properties under preload. MR elastography acquisitions were performed at different pressure levels by externally compressing the tumour with an inflatable balloon. Reference values for tumour fluid pressure and solid stress were acquired with a catheterized pressure transducer. The results, obtained in two liver tumour types with largely different basal mechanical properties, show that the evolution of tumour elasticity under preload is correlated with the tumour solid stress and could be a potential biomarker of tumour pressure.

Yi Sui¹, Arvin Forghanian-Arani¹, Joshua D. Trzasko, ¹, Matthew C. Murphy¹, Phillip J. Rossman¹, Kevin J. Glaser¹, Kiaran P. McGee¹, Armando Manduca², Richard L. Ehman¹, Philip A. Araoz¹, and John III Huston^1
1Radiology, Mayo Clinic, Rochester, MN, United States, ²Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, United States

This study demonstrates the technical feasibility of a 3D radially batched internal navigator echo magnetic resonance elastography (TURBINE-MRE) technique in the brain. The highly efficient TURBINE-MRE approach allows for a true 3D wave displacement field to be acquired over the entire human brain volume in approximately 1.5 minutes.

Pilar Sango Solanas¹, Kevin Tse Ve Koon¹, Eric Van Reeth¹, Cyrielle Caussy², and Olivier Beuf^1
1Univ Lyon, INSA‐Lyon, Université Claude Bernard Lyon 1, UJM-Saint Etienne, CNRS, Inserm, CREATIS UMR 5220, U1206, F‐69616, Lyon, France, Lyon, France, ²Département d’Endocrinologie, Diabète et Nutrition, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, CarMeN, INSERM U1060, INRA U1397, Lyon, France, Lyon, France

Magnetic Resonance Elastography (MRE) is a valuable technique to quantitatively characterize mechanical properties of tissues based on the properties of shear waves propagation. In this study, a radial acquisition MRE sequence potentially able to quantify viscoelastic parameters of tissues whose T2 values are very short is proposed. To this end, an optimal control-based RF pulse is applied with a constant gradient during the mechanical excitation to simultaneously perform spatially selective excitation and motion encoding. Acquisition is started right after, enabling a very short TE. Results on phantom experiments demonstrated the feasibility of our ultra-short echo time MRE technique.

Grace McIlvain¹, Alex M Cerjanic², Anthony G Christodoulou³, Matthew DJ McGarry⁴, and Curtis L Johnson^1
1Biomedical Engineering, University of Delaware, Newark, DE, United States, ²Bioengineering, University of Illinois, Urbana, IL, United States, ³Biomedical Imaging Research Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States, ⁴Thayer School of Engineering, Dartmouth College, Hanover, NH, United States

MR elastography (MRE) has emerged as a sensitive measure of brain health, but due to the need for repeated measures of wave motion, it is a fundamentally long scan. We have developed a method for accurate MRE using spatiotemporal undersampling and low rank joint reconstruction across all samples. We demonstrate the ability to collect accurate MRE data in half the time with under 2% stiffness error. This accelerated method will be used to scan challenging populations, such as those with developmental disabilities, as well as improve achievable resolution and feasibility of multi-frequency or multi-excitation methods. 

Johannes Strasser¹, Martin Soellradl¹, Christian Enzinger¹, and Stefan Ropele^1
1Department of Neurology, Medical University of Graz, Graz, Austria

In MR elastography, the propagation of three-dimensional wave motion is acquired to assess mechanical tissue properties. We here propose an accelerated approach of the multiphase DENSE-MRE acquisition scheme which additionally includes three-dimensional motion encoding besides the multiple phase offsets within one TR. In addition to phantom experiments, this multi-axes encoding concept was also investigated in the human brain in vivo. The gathered wave images and shear modulus maps are confirmed by three consecutive single-axes multiphase DENSE-MRE acquisitions for x-, y- and z-motion encoding direction. With this concept, the acquisition can be accelerated up to a factor of 3.