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Burman Ingeberg M, Van Houten E, Zwanenburg JJM. Estimating the viscoelastic properties of the human brain at 7 T MRI using intrinsic MRE and nonlinear inversion. Hum Brain Mapp 2023; 44:6575-6591. [PMID: 37909395 PMCID: PMC10681656 DOI: 10.1002/hbm.26524] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 10/04/2023] [Accepted: 10/09/2023] [Indexed: 11/03/2023] Open
Abstract
Intrinsic actuation magnetic resonance elastography (MRE) is a phase-contrast MRI technique that allows for in vivo quantification of mechanical properties of the brain by exploiting brain motion that arise naturally due to the cardiac pulse. The mechanical properties of the brain reflect its tissue microstructure, making it a potentially valuable parameter in studying brain disease. The main purpose of this study was to assess the feasibility of reconstructing the viscoelastic properties of the brain using high-quality 7 T MRI displacement measurements, obtained using displacement encoding with stimulated echoes (DENSE) and intrinsic actuation. The repeatability and sensitivity of the method for detecting normal regional variation in brain tissue properties was assessed as secondary goal. The displacement measurements used in this analysis were previously acquired for a separate study, where eight healthy subjects (27 ± 7 years) were imaged with repeated scans (spatial resolution approx. 2 mm isotropic, temporal resolution 75 ms, motion sensitivity 0.35 mm/2π for displacements in anterior-posterior and left-right directions, and 0.7 mm/2π for feet-head displacements). The viscoelastic properties of the brain were estimated using a subzone based non-linear inversion scheme. The results show comparable consistency to that of extrinsic MRE between the viscoelastic property maps obtained from repeated displacement measurements. The shear stiffness maps showed fairly consistent spatial patterns. The whole-brain repeatability coefficient (RC) for shear stiffness was (mean ± standard deviation) 8 ± 8% relative to the mean whole-brain stiffness, and the damping ratio RC was 28 ± 17% relative to the whole-brain damping ratio. The shear stiffness maps showed similar statistically significant regional trends as demonstrated in a publicly available atlas of viscoelastic properties obtained with extrinsic actuation MRE at 50 Hz. The damping ratio maps showed less consistency, likely due to data-model mismatch of describing the brain as a viscoelastic material under low frequencies. While artifacts induced by fluid flow within the brain remain a limitation of the technique in its current state, intrinsic actuation based MRE allow for consistent and repeatable estimation of the mechanical properties of the brain. The method provides enough sensitivity to investigate regional variation in such properties in the normal brain, which is likely sufficient to also investigate pathological changes.
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Meyer T, Kreft B, Bergs J, Antes E, Anders MS, Wellge B, Braun J, Doyley M, Tzschätzsch H, Sack I. Stiffness pulsation of the human brain detected by non-invasive time-harmonic elastography. Front Bioeng Biotechnol 2023; 11:1140734. [PMID: 37650041 PMCID: PMC10463728 DOI: 10.3389/fbioe.2023.1140734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Accepted: 07/19/2023] [Indexed: 09/01/2023] Open
Abstract
Introduction: Cerebral pulsation is a vital aspect of cerebral hemodynamics. Changes in arterial pressure in response to cardiac pulsation cause cerebral pulsation, which is related to cerebrovascular compliance and cerebral blood perfusion. Cerebrovascular compliance and blood perfusion influence the mechanical properties of the brain, causing pulsation-induced changes in cerebral stiffness. However, there is currently no imaging technique available that can directly quantify the pulsation of brain stiffness in real time. Methods: Therefore, we developed non-invasive ultrasound time-harmonic elastography (THE) technique for the real-time detection of brain stiffness pulsation. We used state-of-the-art plane-wave imaging for interleaved acquisitions of shear waves at a frequency of 60 Hz to measure stiffness and color flow imaging to measure cerebral blood flow within the middle cerebral artery. In the second experiment, we used cost-effective lineby-line B-mode imaging to measure the same mechanical parameters without flow imaging to facilitate future translation to the clinic. Results: In 10 healthy volunteers, stiffness increased during the passage of the arterial pulse wave from 4.8% ± 1.8% in the temporal parenchyma to 11% ± 5% in the basal cisterns and 13% ± 9% in the brain stem. Brain stiffness peaked in synchrony with cerebral blood flow at approximately 180 ± 30 ms after the cardiac R-wave. Line-by-line THE provided the same stiffness values with similar time resolution as high-end plane-wave THE, demonstrating the robustness of brain stiffness pulsation as an imaging marker. Discussion: Overall, this study sets the background and provides reference values for time-resolved THE in the human brain as a cost-efficient and easy-touse mechanical biomarker associated with cerebrovascular compliance.
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Affiliation(s)
- Tom Meyer
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Bernhard Kreft
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Judith Bergs
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Erik Antes
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Matthias S. Anders
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Brunhilde Wellge
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité—University Medicine Berlin, Berlin, Germany
| | - Marvin Doyley
- Hajim School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, United States
| | - Heiko Tzschätzsch
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité—University Medicine Berlin, Berlin, Germany
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Bertalan G, Becker J, Tzschätzsch H, Morr A, Herthum H, Shahryari M, Greenhalgh RD, Guo J, Schröder L, Alzheimer C, Budday S, Franze K, Braun J, Sack I. Mechanical behavior of the hippocampus and corpus callosum: An attempt to reconcile ex vivo with in vivo and micro with macro properties. J Mech Behav Biomed Mater 2023; 138:105613. [PMID: 36549250 DOI: 10.1016/j.jmbbm.2022.105613] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2022] [Revised: 11/24/2022] [Accepted: 12/06/2022] [Indexed: 12/13/2022]
Abstract
Mechanical properties of brain tissue are very complex and vary with the species, region, method, and dynamic range, and between in vivo and ex vivo measurements. To reconcile this variability, we investigated in vivo and ex vivo stiffness properties of two distinct regions in the human and mouse brain - the hippocampus (HP) and the corpus callosum (CC) - using different methods. Under quasi-static conditions, we examined ex vivo murine HP and CC by atomic force microscopy (AFM). Between 16 and 40Hz, we investigated the in vivo brains of healthy volunteers by magnetic resonance elastography (MRE) in a 3-T clinical scanner. At high-frequency stimulation between 1000 and 1400Hz, we investigated the murine HP and CC ex vivo and in vivo with MRE in a 7-T preclinical system. HP and CC showed pronounced stiffness dispersion, as reflected by a factor of 32-36 increase in shear modulus from AFM to low-frequency human MRE and a 25-fold higher shear wave velocity in murine MRE than in human MRE. At low frequencies, HP was softer than CC, in both ex vivo mouse specimens (p < 0.05) and in vivo human brains (p < 0.01) while, at high frequencies, CC was softer than HP under in vivo (p < 0.01) and ex vivo (p < 0.05) conditions. The standard linear solid model comprising three elements reproduced the observed HP and CC stiffness dispersions, while other two- and three-element models failed. Our results indicate a remarkable consistency of brain stiffness across species, ex vivo and in vivo states, and different measurement techniques when marked viscoelastic dispersion properties combining equilibrium and non-equilibrium mechanical elements are considered.
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Affiliation(s)
- Gergerly Bertalan
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Julia Becker
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Heiko Tzschätzsch
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Anna Morr
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Helge Herthum
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Mehrgan Shahryari
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ryan D Greenhalgh
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Jing Guo
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Leif Schröder
- Translational Molecular Imaging, Deutsches Krebsforschungszentrum, Heidelberg, Germany
| | - Christian Alzheimer
- Institute of Physiology and Pathophysiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Silvia Budday
- Institute of Applied Mechanics, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Kristian Franze
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom; Institute of Medical Physics, Friedrich-Alexander-Universität, Erlangen-Nürnberg, Erlangen, Germany; Max-Planck-Zentrum für Physik und Medizin, Erlangen, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Berlin, Germany.
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Borda E, Medagoda DI, Airaghi Leccardi MJI, Zollinger EG, Ghezzi D. Conformable neural interface based on off-stoichiometry thiol-ene-epoxy thermosets. Biomaterials 2023; 293:121979. [PMID: 36586146 DOI: 10.1016/j.biomaterials.2022.121979] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2022] [Revised: 11/29/2022] [Accepted: 12/21/2022] [Indexed: 12/28/2022]
Abstract
Off-stoichiometry thiol-ene-epoxy (OSTE+) thermosets show low permeability to gases and little absorption of dissolved molecules, allow direct low-temperature dry bonding without surface treatments, have a low Young's modulus, and can be manufactured via UV polymerisation. For these reasons, OSTE+ thermosets have recently gained attention for the rapid prototyping of microfluidic chips. Moreover, their compatibility with standard clean-room processes and outstanding mechanical properties make OSTE+ an excellent candidate as a novel material for neural implants. Here we exploit OSTE+ to manufacture a conformable multilayer micro-electrocorticography array with 16 platinum electrodes coated with platinum black. The mechanical properties allow conformability to curved surfaces such as the brain. The low permeability and strong adhesion between layers improve the stability of the device. Acute experiments in mice show the multimodal capacity of the array to record and stimulate the neural tissue by smoothly conforming to the mouse cortex. Devices are not cytotoxic, and immunohistochemistry stainings reveal only modest foreign body reaction after two and six weeks of chronic implantation. This work introduces OSTE+ as a promising material for implantable neural interfaces.
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Affiliation(s)
- Eleonora Borda
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, Switzerland
| | - Danashi Imani Medagoda
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, Switzerland
| | - Marta Jole Ildelfonsa Airaghi Leccardi
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, Switzerland
| | - Elodie Geneviève Zollinger
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, Switzerland
| | - Diego Ghezzi
- Medtronic Chair in Neuroengineering, Center for Neuroprosthetics and Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne, Switzerland.
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5
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Herthum H, Hetzer S, Kreft B, Tzschätzsch H, Shahryari M, Meyer T, Görner S, Neubauer H, Guo J, Braun J, Sack I. Cerebral tomoelastography based on multifrequency MR elastography in two and three dimensions. Front Bioeng Biotechnol 2022; 10:1056131. [PMID: 36532573 PMCID: PMC9755504 DOI: 10.3389/fbioe.2022.1056131] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 11/21/2022] [Indexed: 09/01/2023] Open
Abstract
Purpose: Magnetic resonance elastography (MRE) generates quantitative maps of the mechanical properties of biological soft tissues. However, published values obtained by brain MRE vary largely and lack detail resolution, due to either true biological effects or technical challenges. We here introduce cerebral tomoelastography in two and three dimensions for improved data consistency and detail resolution while considering aging, brain parenchymal fraction (BPF), systolic blood pressure, and body mass index (BMI). Methods: Multifrequency MRE with 2D- and 3D-tomoelastography postprocessing was applied to the brains of 31 volunteers (age range: 22-61 years) for analyzing the coefficient of variation (CV) and effects of biological factors. Eleven volunteers were rescanned after 1 day and 1 year to determine intraclass correlation coefficient (ICC) and identify possible long-term changes. Results: White matter shear wave speed (SWS) was slightly higher in 2D-MRE (1.28 ± 0.02 m/s) than 3D-MRE (1.22 ± 0.05 m/s, p < 0.0001), with less variation after 1 day in 2D (0.33 ± 0.32%) than in 3D (0.96 ± 0.66%, p = 0.004), which was also reflected in a slightly lower CV and higher ICC in 2D (1.84%, 0.97 [0.88-0.99]) than in 3D (3.89%, 0.95 [0.76-0.99]). Remarkably, 3D-MRE was sensitive to a decrease in white matter SWS within only 1 year, whereas no change in white matter volume was observed during this follow-up period. Across volunteers, stiffness correlated with age and BPF, but not with blood pressure and BMI. Conclusion: Cerebral tomoelastography provides high-resolution viscoelasticity maps with excellent consistency. Brain MRE in 2D shows less variation across volunteers in shorter scan times than 3D-MRE, while 3D-MRE appears to be more sensitive to subtle biological effects such as aging.
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Affiliation(s)
- Helge Herthum
- Berlin Center for Advanced Neuroimaging, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
- Institute of Medical Informatics, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Stefan Hetzer
- Berlin Center for Advanced Neuroimaging, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
- Bernstein Center for Computational Neuroscience, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Bernhard Kreft
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Heiko Tzschätzsch
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Mehrgan Shahryari
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Tom Meyer
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Steffen Görner
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Hennes Neubauer
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Jing Guo
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité—Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Berlin Institute of Health, Humboldt-Universität zu Berlin, Berlin, Germany
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6
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Measurement of Pulsating Flow Using a Self-Attachable Flexible Strain Sensor Based on Adhesive PDMS and CNT. CHEMOSENSORS 2022. [DOI: 10.3390/chemosensors10050187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Accurate monitoring is needed for pulsating flow in many healthcare and bio applications. Specifically, real-time monitoring of pulsating blood flow provides rich information regarding a patient’s health conditions. This paper proposes a flexible strain sensor capable of detecting the pulsating fluid flow by directly measuring the circumferential strain induced by a rapid change in the flow rate. The thin and flexible strain sensor consists of a polydimethylsiloxane (PDMS) with a Triton-X treatment to enhance the adhesive property and multi-walled carbon nanotubes (MWCNT) as the piezoresistive sensing layer. MWCNT integration implements a simple spray-coating method. The adhesive PDMS/CNT strain sensor exhibits a highly adhesive nature and can be attached to a silicone tube’s curved surface. By analyzing the theoretical modeling based on fluid energy equation and solid mechanics, strains induced on the soft tube by the change in flow rate, viscosity, and fluid density can be predicted. We performed the flow rate measurement at varying fluid-flow rates and liquid viscosities, and the results match our prediction. The sensitivity and limit of detection of the presented strain sensor are about 0.55 %min/L and 0.4 L/min, respectively. Both the calculation and experiment confirm that the sensor resistance is most sensitive to the fluid-flow rate, thus, enabling the accurate tracking of pulsating fluids’ flow rate, regardless of the viscosity or density.
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7
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Sloots JJ, Froeling M, Biessels GJ, Zwanenburg JJM. Dynamic brain ADC variations over the cardiac cycle and their relation to tissue strain assessed with DENSE at high-field MRI. Magn Reson Med 2022; 88:266-279. [PMID: 35344595 PMCID: PMC9315037 DOI: 10.1002/mrm.29209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Revised: 12/10/2021] [Accepted: 02/08/2022] [Indexed: 12/11/2022]
Abstract
Purpose The ADC of brain tissue slightly varies over the cardiac cycle. This variation could reflect physiology, including mixing of the interstitial fluid, relevant for brain waste clearance. However, it is known from cardiac diffusion imaging that tissue deformation by itself affects the magnitude of the MRI signal, leading to artificial ADC variations as well. This study investigates to what extent tissue deformation causes artificial ADC variations in the brain. Theory and Methods We implemented a high‐field MRI sequence with stimulated echo acquisition mode that simultaneously measures brain tissue deformation and ADC. Based on the measured tissue deformation, we simulated the artificial ADC variation by combining established theoretical frameworks and compared the results with the measured ADC variation. We acquired data in 8 healthy volunteers with diffusion weighting b = 300 and b = 1000 s/mm2. Results Apparent diffusion coefficient variation was largest in the feet‐to‐head direction and showed the largest deviation from the mean ADC at peak systole. Artificial ADC variation estimated from tissue deformation was 1.3 ± 0.37·10−5 mm2/s in the feet‐to‐head direction for gray matter, and 0.75 ± 0.29·10−5 mm2/s for white matter. The measured ADC variation in the feet‐to‐head direction was 5.6·10−5 ± 1.5·10−5 mm2/s for gray matter and 3.2·10−5 ± 1.0·10−5 mm2/s for white matter, which was a factor of 3.5 ± 0.82 and 3.4 ± 0.57 larger than the artificial diffusion variations. The measured diffusion variations in the right‐to‐left/anterior‐to‐posterior direction were a factor of 1.5 ± 1.0/1.7 ± 1.4 and 2.0 ± 0.91/2.5 ± 0.94 larger than the artificial diffusion variations for gray matter and white matter, respectively. Conclusion Apparent diffusion coefficient variations in the brain likely largely reflect physiology.
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Affiliation(s)
- Jacob-Jan Sloots
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Martijn Froeling
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Geert Jan Biessels
- Department of Neurology, UMC Utrecht Brain Center, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jaco J M Zwanenburg
- Center for Image Sciences, University Medical Center Utrecht, Utrecht, The Netherlands
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8
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Kreft B, Tzschätzsch H, Shahryari M, Haffner P, Braun J, Sack I, Streitberger KJ. Noninvasive Detection of Intracranial Hypertension by Novel Ultrasound Time-Harmonic Elastography. Invest Radiol 2022; 57:77-84. [PMID: 34380993 DOI: 10.1097/rli.0000000000000817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE A method for measuring intracranial pressure (ICP) noninvasively has long been sought after in neurology and neurosurgery. Treatment failure in individuals presenting with unspecific symptoms such as headache, gait disturbance, or visual impairment occurring in response to increased ICP can lead to irreversible brain injury, progressive disability, and death. Guidelines for diagnostic ICP measurement recommend intracranial placement of pressure tip catheters or lumbar puncture (LP) despite their invasiveness and possible complications. As ICP fluctuations are closely associated with changes in brain stiffness, ultrasound elastography could be a valid method to detect ICP noninvasively and with short examination times. MATERIALS AND METHODS In this pilot study, we have investigated the use of time-harmonic shear waves, introduced into the brain by an external shaker, and measured in real-time by transtemporal ultrasound, for deducing a noninvasive imaging marker sensitive to elevated ICP. To this end, we developed cerebral ultrasound time-harmonic elastography for the noninvasive quantification of shear wave speed (SWS) as a surrogate marker of cerebral stiffness in a short examination time of a few minutes. RESULTS We found that SWS in patients enrolled for LP with confirmed intracranial hypertension was 1.81 ± 0.10 m/s, distinguishing them from healthy volunteers with excellent diagnostic accuracy (1.55 ± 0.08 m/s; P < 0.001; area under the curve, 0.99). Interestingly, values in symptomatic patients decreased to normal stiffness immediately after LP (1.56 ± 0.06 m/s, P < 0.001). Moreover, invasively measured opening pressure correlated with SWS measured before LP and liquid volume drained through the spinal tap with the SWS difference between the 2 measurements. CONCLUSIONS Collectively, our results suggest a tight link between cerebral stiffness and ICP and demonstrate that intracranial hypertension can be detected noninvasively within short examination times, opening avenues for diagnostic applications of cerebral ultrasound time-harmonic elastography in neurology and emergency medicine.
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Affiliation(s)
| | | | | | - Paula Haffner
- Department of Neurology, Charité-Universitätsmedizin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
| | | | | | - Kaspar-Josche Streitberger
- Department of Neurology, Charité-Universitätsmedizin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Berlin, Germany
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9
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Ozkaya E, Triolo ER, Rezayaraghi F, Abderezaei J, Meinhold W, Hong K, Alipour A, Kennedy P, Fleysher L, Ueda J, Balchandani P, Eriten M, Johnson CL, Yang Y, Kurt M. Brain-mimicking phantom for biomechanical validation of motion sensitive MR imaging techniques. J Mech Behav Biomed Mater 2021; 122:104680. [PMID: 34271404 DOI: 10.1016/j.jmbbm.2021.104680] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Revised: 05/07/2021] [Accepted: 06/30/2021] [Indexed: 10/20/2022]
Abstract
Motion sensitive MR imaging techniques allow for the non-invasive evaluation of biological tissues by using different excitation schemes, including physiological/intrinsic motions caused by cardiac pulsation or respiration, and vibrations caused by an external actuator. The mechanical biomarkers extracted through these imaging techniques have been shown to hold diagnostic value for various neurological disorders and conditions. Amplified MRI (aMRI), a cardiac gated imaging technique, can help track and quantify low frequency intrinsic motion of the brain. As for high frequency actuation, the mechanical response of brain tissue can be measured by applying external high frequency actuation in combination with a motion sensitive MR imaging sequence called Magnetic Resonance Elastography (MRE). Due to the frequency-dependent behavior of brain mechanics, there is a need to develop brain phantom models that can mimic the broadband mechanical response of the brain in order to validate motion-sensitive MR imaging techniques. Here, we have designed a novel phantom test setup that enables both the low and high frequency responses of a brain-mimicking phantom to be captured, allowing for both aMRI and MRE imaging techniques to be applied on the same phantom model. This setup combines two different vibration sources: a pneumatic actuator, for low frequency/intrinsic motion (1 Hz) for use in aMRI, and a piezoelectric actuator for high frequency actuation (30-60 Hz) for use in MRE. Our results show that in MRE experiments performed from 30 Hz through 60 Hz, propagating shear waves attenuate faster at higher driving frequencies, consistent with results in the literature. Furthermore, actuator coupling has a substantial effect on wave amplitude, with weaker coupling causing lower amplitude wave field images, specifically shown in the top-surface shear loading configuration. For intrinsic actuation, our results indicate that aMRI linearly amplifies motion up to at least an amplification factor of 9 for instances of both visible and sub-voxel motion, validated by varying power levels of pneumatic actuation (40%-80% power) under MR, and through video analysis outside the MRI scanner room. While this investigation used a homogeneous brain-mimicking phantom, our setup can be used to study the mechanics of non-homogeneous phantom configurations with bio-interfaces in the future.
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Affiliation(s)
- E Ozkaya
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
| | - E R Triolo
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - F Rezayaraghi
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - J Abderezaei
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - W Meinhold
- The George W. Woodruff of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - K Hong
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - A Alipour
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - P Kennedy
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - L Fleysher
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - J Ueda
- The George W. Woodruff of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - P Balchandani
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - M Eriten
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - C L Johnson
- Department of Biomedical Engineering, University of Deleware, Newark, DE, 19716, USA
| | - Y Yang
- BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - M Kurt
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030, USA; BioMedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
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10
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Lilaj L, Herthum H, Meyer T, Shahryari M, Bertalan G, Caiazzo A, Braun J, Fischer T, Hirsch S, Sack I. Inversion-recovery MR elastography of the human brain for improved stiffness quantification near fluid-solid boundaries. Magn Reson Med 2021; 86:2552-2561. [PMID: 34184306 DOI: 10.1002/mrm.28898] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 05/10/2021] [Accepted: 06/02/2021] [Indexed: 12/31/2022]
Abstract
PURPOSE In vivo MR elastography (MRE) holds promise as a neuroimaging marker. In cerebral MRE, shear waves are introduced into the brain, which also stimulate vibrations in adjacent CSF, resulting in blurring and biased stiffness values near brain surfaces. We here propose inversion-recovery MRE (IR-MRE) to suppress CSF signal and improve stiffness quantification in brain surface areas. METHODS Inversion-recovery MRE was demonstrated in agar-based phantoms with solid-fluid interfaces and 11 healthy volunteers using 31.25-Hz harmonic vibrations. It was performed by standard single-shot, spin-echo EPI MRE following 2800-ms IR preparation. Wave fields were acquired in 10 axial slices and analyzed for shear wave speed (SWS) as a surrogate marker of tissue stiffness by wavenumber-based multicomponent inversion. RESULTS Phantom SWS values near fluid interfaces were 7.5 ± 3.0% higher in IR-MRE than MRE (P = .01). In the brain, IR-MRE SNR was 17% lower than in MRE, without influencing parenchymal SWS (MRE: 1.38 ± 0.02 m/s; IR-MRE: 1.39 ± 0.03 m/s; P = .18). The IR-MRE tissue-CSF interfaces appeared sharper, showing 10% higher SWS near brain surfaces (MRE: 1.01 ± 0.03 m/s; IR-MRE: 1.11 ± 0.01 m/s; P < .001) and 39% smaller ventricle sizes than MRE (P < .001). CONCLUSIONS Our results show that brain MRE is affected by fluid oscillations that can be suppressed by IR-MRE, which improves the depiction of anatomy in stiffness maps and the quantification of stiffness values in brain surface areas. Moreover, we measured similar stiffness values in brain parenchyma with and without fluid suppression, which indicates that shear wavelengths in solid and fluid compartments are identical, consistent with the theory of biphasic poroelastic media.
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Affiliation(s)
- Ledia Lilaj
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Helge Herthum
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Tom Meyer
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Mehrgan Shahryari
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Gergely Bertalan
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Alfonso Caiazzo
- Weierstrass Institute for Applied Analysis and Stochastics, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Thomas Fischer
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Hirsch
- Berlin Center for Advanced Neuroimaging, Charité-Universitätsmedizin Berlin, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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11
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Lorentz force induced shear waves for magnetic resonance elastography applications. Sci Rep 2021; 11:12785. [PMID: 34140568 PMCID: PMC8211670 DOI: 10.1038/s41598-021-91895-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 06/02/2021] [Indexed: 11/08/2022] Open
Abstract
Quantitative mechanical properties of biological tissues can be mapped using the shear wave elastography technique. This technology has demonstrated a great potential in various organs but shows a limit due to wave attenuation in biological tissues. An option to overcome the inherent loss in shear wave magnitude along the propagation pathway may be to stimulate tissues closer to regions of interest using alternative motion generation techniques. The present study investigated the feasibility of generating shear waves by applying a Lorentz force directly to tissue mimicking samples for magnetic resonance elastography applications. This was done by combining an electrical current with the strong magnetic field of a clinical MRI scanner. The Local Frequency Estimation method was used to assess the real value of the shear modulus of tested phantoms from Lorentz force induced motion. Finite elements modeling of reported experiments showed a consistent behavior but featured wavelengths larger than measured ones. Results suggest the feasibility of a magnetic resonance elastography technique based on the Lorentz force to produce an shear wave source.
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12
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Terem I, Dang L, Champagne A, Abderezaei J, Pionteck A, Almadan Z, Lydon AM, Kurt M, Scadeng M, Holdsworth SJ. 3D amplified MRI (aMRI). Magn Reson Med 2021; 86:1674-1686. [PMID: 33949713 PMCID: PMC8252598 DOI: 10.1002/mrm.28797] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2020] [Revised: 02/18/2021] [Accepted: 03/17/2021] [Indexed: 12/17/2022]
Abstract
Purpose Amplified MRI (aMRI) has been introduced as a new method of detecting and visualizing pulsatile brain motion in 2D. Here, we improve aMRI by introducing a novel 3D aMRI approach. Methods 3D aMRI was developed and tested for its ability to amplify sub‐voxel motion in all three directions. In addition, 3D aMRI was qualitatively compared to 2D aMRI on multi‐slice and 3D (volumetric) balanced steady‐state free precession cine data and phase contrast (PC‐MRI) acquired on healthy volunteers at 3T. Optical flow maps and 4D animations were produced from volumetric 3D aMRI data. Results 3D aMRI exhibits better image quality and fewer motion artifacts compared to 2D aMRI. The tissue motion was seen to match that of PC‐MRI, with the predominant brain tissue displacement occurring in the cranial‐caudal direction. Optical flow maps capture the brain tissue motion and display the physical change in shape of the ventricles by the relative movement of the surrounding tissues. The 4D animations show the complete brain tissue and cerebrospinal fluid (CSF) motion, helping to highlight the “piston‐like” motion of the ventricles. Conclusions Here, we introduce a novel 3D aMRI approach that enables one to visualize amplified cardiac‐ and CSF‐induced brain motion in striking detail. 3D aMRI captures brain motion with better image quality than 2D aMRI and supports a larger amplification factor. The optical flow maps and 4D animations of 3D aMRI may open up exciting applications for neurological diseases that affect the biomechanics of the brain and brain fluids.
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Affiliation(s)
- Itamar Terem
- Department of Electrical Engineering, Stanford University, Stanford, California, USA.,Department of Structural Biology, Stanford University, Stanford, California, USA
| | - Leo Dang
- Department of Anatomy and Medical Imaging & Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,Mātai Medical Research Institute, Gisborne-Tairāwhiti, New Zealand
| | - Allen Champagne
- Centre for Neuroscience Studies, Queen's University, Kingston, Ontario, Canada
| | - Javid Abderezaei
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
| | - Aymeric Pionteck
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA
| | - Zainab Almadan
- Department of Anatomy and Medical Imaging & Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
| | - Anna-Maria Lydon
- Centre for Advanced MRI, University of Auckland, Auckland, New Zealand
| | - Mehmet Kurt
- Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, New Jersey, USA.,Biomedical Engineering and Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Miriam Scadeng
- Department of Anatomy and Medical Imaging & Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,Mātai Medical Research Institute, Gisborne-Tairāwhiti, New Zealand.,Department of Radiology, University of California, San Diego, California, USA
| | - Samantha J Holdsworth
- Department of Anatomy and Medical Imaging & Centre for Brain Research, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.,Mātai Medical Research Institute, Gisborne-Tairāwhiti, New Zealand
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13
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Development, calibration, and testing of 3D amplified MRI (aMRI) for the quantification of intrinsic brain motion. BRAIN MULTIPHYSICS 2021. [DOI: 10.1016/j.brain.2021.100022] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
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14
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Sloots JJ, Biessels GJ, de Luca A, Zwanenburg JJM. Strain Tensor Imaging: Cardiac-induced brain tissue deformation in humans quantified with high-field MRI. Neuroimage 2021; 236:118078. [PMID: 33878376 DOI: 10.1016/j.neuroimage.2021.118078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 02/02/2021] [Accepted: 04/07/2021] [Indexed: 11/15/2022] Open
Abstract
The cardiac cycle induces blood volume pulsations in the cerebral microvasculature that cause subtle deformation of the surrounding tissue. These tissue deformations are highly relevant as a potential source of information on the brain's microvasculature as well as of tissue condition. Besides, cyclic brain tissue deformations may be a driving force in clearance of brain waste products. We have developed a high-field magnetic resonance imaging (MRI) technique to capture these tissue deformations with full brain coverage and sufficient signal-to-noise to derive the cardiac-induced strain tensor on a voxel by voxel basis, that could not be assessed non-invasively before. We acquired the strain tensor with 3 mm isotropic resolution in 9 subjects with repeated measurements for 8 subjects. The strain tensor yielded both positive and negative eigenvalues (principle strains), reflecting the Poison effect in tissue. The principle strain associated with expansion followed the known funnel shaped brain motion pattern pointing towards the foramen magnum. Furthermore, we evaluate two scalar quantities from the strain tensor: the volumetric strain and octahedral shear strain. These quantities showed consistent patterns between subjects, and yielded repeatable results: the peak systolic volumetric strain (relative to end-diastolic strain) was 4.19⋅10-4 ± 0.78⋅10-4 and 3.98⋅10-4 ± 0.44⋅10-4 (mean ± standard deviation for first and second measurement, respectively), and the peak octahedral shear strain was 2.16⋅10-3 ± 0.31⋅10-3 and 2.31⋅10-3 ± 0.38⋅10-3, for the first and second measurement, respectively. The volumetric strain was typically highest in the cortex and lowest in the periventricular white matter, while anisotropy was highest in the subcortical white matter and basal ganglia. This technique thus reveals new, regional information on the brain's cardiac-induced deformation characteristics, and has the potential to advance our understanding of the role of microvascular pulsations in health and disease.
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Affiliation(s)
| | - Geert Jan Biessels
- Neurology, UMC Utrecht Brain Center, University Medical Center Utrecht, the Netherlands
| | - Alberto de Luca
- Neurology, UMC Utrecht Brain Center, University Medical Center Utrecht, the Netherlands
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15
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Arani A, Manduca A, Ehman RL, Huston Iii J. Harnessing brain waves: a review of brain magnetic resonance elastography for clinicians and scientists entering the field. Br J Radiol 2021; 94:20200265. [PMID: 33605783 PMCID: PMC8011257 DOI: 10.1259/bjr.20200265] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Brain magnetic resonance elastography (MRE) is an imaging technique capable of accurately and non-invasively measuring the mechanical properties of the living human brain. Recent studies have shown that MRE has potential to provide clinically useful information in patients with intracranial tumors, demyelinating disease, neurodegenerative disease, elevated intracranial pressure, and altered functional states. The objectives of this review are: (1) to give a general overview of the types of measurements that have been obtained with brain MRE in patient populations, (2) to survey the tools currently being used to make these measurements possible, and (3) to highlight brain MRE-based quantitative biomarkers that have the highest potential of being adopted into clinical use within the next 5 to 10 years. The specifics of MRE methodology strategies are described, from wave generation to material parameter estimations. The potential clinical role of MRE for characterizing and planning surgical resection of intracranial tumors and assessing diffuse changes in brain stiffness resulting from diffuse neurological diseases and altered intracranial pressure are described. In addition, the emerging technique of functional MRE, the role of artificial intelligence in MRE, and promising applications of MRE in general neuroscience research are presented.
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Affiliation(s)
- Arvin Arani
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Armando Manduca
- Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
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16
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Herthum H, Dempsey SCH, Samani A, Schrank F, Shahryari M, Warmuth C, Tzschätzsch H, Braun J, Sack I. Superviscous properties of the in vivo brain at large scales. Acta Biomater 2021; 121:393-404. [PMID: 33326885 DOI: 10.1016/j.actbio.2020.12.027] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/08/2020] [Accepted: 12/10/2020] [Indexed: 12/28/2022]
Abstract
There is growing awareness that brain mechanical properties are important for neural development and health. However, published values of brain stiffness differ by orders of magnitude between static measurements and in vivo magnetic resonance elastography (MRE), which covers a dynamic range over several frequency decades. We here show that there is no fundamental disparity between static mechanical tests and in vivo MRE when considering large-scale properties, which encompass the entire brain including fluid filled compartments. Using gradient echo real-time MRE, we investigated the viscoelastic dispersion of the human brain in, so far, unexplored dynamic ranges from intrinsic brain pulsations at 1 Hz to ultralow-frequency vibrations at 5, 6.25, 7.8 and 10 Hz to the normal frequency range of MRE of 40 Hz. Surprisingly, we observed variations in brain stiffness over more than two orders of magnitude, suggesting that the in vivo human brain is superviscous on large scales with very low shear modulus of 42±13 Pa and relatively high viscosity of 6.6±0.3 Pa∙s according to the two-parameter solid model. Our data shed light on the crucial role of fluid compartments including blood vessels and cerebrospinal fluid (CSF) for whole brain properties and provide, for the first time, an explanation for the variability of the mechanical brain responses to manual palpation, local indentation, and high-dynamic tissue stimulation as used in elastography.
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17
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Abderezaei J, Martinez J, Terem I, Fabris G, Pionteck A, Yang Y, Holdsworth SJ, Nael K, Kurt M. Amplified Flow Imaging (aFlow): A Novel MRI-Based Tool to Unravel the Coupled Dynamics Between the Human Brain and Cerebrovasculature. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:4113-4123. [PMID: 32746150 DOI: 10.1109/tmi.2020.3012932] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
With each heartbeat, periodic variations in arterial blood pressure are transmitted along the vasculature, resulting in localized deformations of the arterial wall and its surrounding tissue. Quantification of such motions may help understand various cerebrovascular conditions, yet it has proven technically challenging thus far. We introduce a new image processing algorithm called amplified Flow (aFlow) which allows to study the coupled brain-blood flow motion by combining the amplification of cine and 4D flow MRI. By incorporating a modal analysis technique known as dynamic mode decomposition into the algorithm, aFlow is able to capture the characteristics of transient events present in the brain and arterial wall deformation. Validating aFlow, we tested it on phantom simulations mimicking arterial walls motion and observed that aFlow displays almost twice higher SNR than its predecessor amplified MRI (aMRI). We then applied aFlow to 4D flow and cine MRI datasets of 5 healthy subjects, finding high correlations between blood flow velocity and tissue deformation in selected brain regions, with correlation values r = 0.61 , 0.59, 0.52 for the pons, frontal and occipital lobe ( ). Finally, we explored the potential diagnostic applicability of aFlow by studying intracranial aneurysm dynamics, which seems to be indicative of rupture risk. In two patients, aFlow successfully visualized the imperceptible aneurysm wall motion, additionally quantifying the increase in the high frequency wall displacement after a one-year follow-up period (20%, 76%). These preliminary data suggest that aFlow may provide a novel imaging biomarker for the assessment of aneurysms evolution, with important potential diagnostic implications.
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18
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Li J, Sehrawat TS, Chen J, Hilscher MB, Glaser KJ, Arab JP, De Assuncao TM, Simonetto DA, Mounajjed T, Manduca A, Ehman RL, Shah VH, Yin M. Quantitative assessment of portal hypertension with bi-parametric dual-frequency hepatic MR elastography in mouse models. Eur Radiol 2020; 31:2303-2311. [PMID: 33026502 DOI: 10.1007/s00330-020-07341-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 08/28/2020] [Accepted: 09/22/2020] [Indexed: 12/15/2022]
Abstract
OBJECTIVES To determine the potential of bi-parametric dual-frequency hepatic MR elastography (MRE) for predicting portal pressure (PP) in mouse models of portal hypertension (PHTN) with the presence of varying hepatic fibrosis. METHODS We studied 73 wild-type male mice, including 22 mice with hepatic congestion, 20 mice with cholestatic liver injury, and 31 age-matched sham mice. Hepatic shear stiffness (SS) and volumetric strain (VS) were calculated by 3D MRE acquired at 80 and 200 Hz. We measured PP immediately after MRE. Liver fibrosis was verified by hydroxyproline assay. We predicted PP by fitting generalized linear models with single- and dual-frequency SS and VS, respectively. The relationship between predicted and actual PP was evaluated by Spearman's correlation. We compared the prediction accuracy of portal hypertension for all models with DeLong tests at a significance level of 0.05. RESULTS Animals with congestive or cholestatic liver disease developed significant PHTN and hepatic fibrosis to varying degrees. In both models, SS increased, while VS decreased significantly compared with shams. All bi-parametric models had high diagnostic accuracy for PHTN. The dual-frequency models (AUCs: 0.90 [81-95%], 0.91 [81-95%]) had substantially or significantly higher accuracy than single-frequency ones (AUCs: 0.83 [71-91%], and 0.78 [66-87%]). The predicted PP of dual-frequency models also showed stronger correlations with actual PP than single-frequency predictions. CONCLUSIONS The bi-parametric dual-frequency model improved the diagnostic accuracy of liver MRE in diagnosing PHTN in preclinical models. This technical advance has the potential to monitor PHTN progression and treatment efficacy in the presence of varying fibrosis. KEY POINTS • Bi-parametric hepatic MR elastography can predict portal pressure. • The prediction models of shear stiffness and volumetric strain with dual-frequency measurements demonstrate high diagnostic accuracy (AUCs > 0.9) in two different portal hypertension mouse models with varying fibrosis.
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Affiliation(s)
- Jiahui Li
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Tejasav S Sehrawat
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Jingbiao Chen
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Moira B Hilscher
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Kevin J Glaser
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Juan P Arab
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | | | - Douglas A Simonetto
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | | | - Armando Manduca
- Department of Radiology, Mayo Clinic, Rochester, MN, USA.,Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, MN, USA
| | | | - Vijay H Shah
- Division of Gastroenterology and Hepatology, Mayo Clinic, Rochester, MN, USA
| | - Meng Yin
- Department of Radiology, Mayo Clinic, Rochester, MN, USA.
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19
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Lilaj L, Fischer T, Guo J, Braun J, Sack I, Hirsch S. Separation of fluid and solid shear wave fields and quantification of coupling density by magnetic resonance poroelastography. Magn Reson Med 2020; 85:1655-1668. [PMID: 32902011 DOI: 10.1002/mrm.28507] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Revised: 08/14/2020] [Accepted: 08/14/2020] [Indexed: 11/08/2022]
Abstract
PURPOSE Biological soft tissues often have a porous architecture comprising fluid and solid compartments. Upon displacement through physiological or externally induced motion, the relative motion of these compartments depends on poroelastic parameters, such as coupling density ( ρ 12 ) and tissue porosity. This study introduces inversion recovery MR elastography (IR-MRE) (1) to quantify porosity defined as fluid volume over total volume, (2) to separate externally induced shear strain fields of fluid and solid compartments, and (3) to quantify coupling density assuming a biphasic behavior of in vivo brain tissue. THEORY AND METHODS Porosity was measured in eight tofu phantoms and gray matter (GM) and white matter (WM) of 21 healthy volunteers. Porosity of tofu was compared to values obtained by fluid draining and microscopy. Solid and fluid shear-strain amplitudes and ρ 12 were estimated both in phantoms and in in vivo brain. RESULTS T1 -based measurement of tofu porosity agreed well with reference values (R = 0.99, P < .01). Brain tissue porosity was 0.14 ± 0.02 in GM and 0.05 ± 0.01 in WM (P < .001). Fluid shear strain was found to be phase-locked with solid shear strain but had lower amplitudes in both tofu phantoms and brain tissue (P < .05). In accordance with theory, tofu and brain ρ 12 were negative. CONCLUSION IR-MRE allowed for the first time separation of shear strain fields of solid and fluid compartments for measuring coupling density according to the biphasic theory of poroelasticity. Thus, IR-MRE opens horizons for poroelastography-derived imaging markers that can be used in basic research and diagnostic applications.
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Affiliation(s)
- Ledia Lilaj
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Thomas Fischer
- Department of Radiology, Interdisciplinary Ultrasound Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jing Guo
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Hirsch
- Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany
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20
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Schrank F, Warmuth C, Tzschätzsch H, Kreft B, Hirsch S, Braun J, Elgeti T, Sack I. Cardiac-gated steady-state multifrequency magnetic resonance elastography of the brain: Effect of cerebral arterial pulsation on brain viscoelasticity. J Cereb Blood Flow Metab 2020; 40:991-1001. [PMID: 31142226 PMCID: PMC7181097 DOI: 10.1177/0271678x19850936] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 03/29/2019] [Accepted: 04/22/2019] [Indexed: 12/12/2022]
Abstract
In-vivo brain viscoelasticity measured by magnetic resonance elastography (MRE) is a sensitive imaging marker for long-term biophysical changes in brain tissue due to aging and disease; however, it is still unknown whether MRE can reveal short-term periodic alterations of brain viscoelasticity related to cerebral arterial pulsation (CAP). We developed cardiac-gated steady-state MRE (ssMRE) with spiral readout and stroboscopic sampling of continuously induced mechanical vibrations in the brain at 20, 31.25, and 40 Hz frequencies. Maps of magnitude |G*| and phase ϕ of the complex shear modulus were generated by multifrequency dual visco-elasto inversion with a temporal resolution of 40 ms over 4 s. The method was tested in 12 healthy volunteers. During cerebral systole, |G*| decreased by 6.6 ± 1.9% (56 ± 22 Pa, p < 0.001, mean ± SD), whereas ϕ increased by 0.5 ± 0.5% (0.006 ± 0.005 rad, p = 0.002). The effect size of CAP-induced softening slightly decreased with age by 0.10 ± 0.05% per year (p = 0.04), indicating lower cerebral vascular compliance in older individuals. Our data show for the first time that the brain softens and becomes more viscous during systole, possibly due to an effect of CAP-induced arterial expansion and increased blood volume on effective-medium tissue properties. This sensitivity to vascular-solid tissue interactions makes ssMRE potentially useful for detection of cerebral vascular disease.
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Affiliation(s)
- Felix Schrank
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
| | - Carsten Warmuth
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
| | - Heiko Tzschätzsch
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
| | - Bernhard Kreft
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Hirsch
- Berlin Center for Advanced Neuroimaging,
Charité – Universitätsmedizin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics,
Charité – Universitätsmedizin Berlin, Berlin, Germany
| | - Thomas Elgeti
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité –
Universitätsmedizin Berlin, Berlin, Germany
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21
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Sloots JJ, Biessels GJ, Zwanenburg JJM. Cardiac and respiration-induced brain deformations in humans quantified with high-field MRI. Neuroimage 2020; 210:116581. [PMID: 31982580 DOI: 10.1016/j.neuroimage.2020.116581] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Revised: 12/23/2019] [Accepted: 01/20/2020] [Indexed: 01/20/2023] Open
Abstract
Microvascular blood volume pulsations due to the cardiac and respiratory cycles induce brain tissue deformation and, as such, are considered to drive the brain's waste clearance system. We have developed a high-field magnetic resonance imaging (MRI) technique to quantify both cardiac and respiration-induced tissue deformations, which could not be assessed noninvasively before. The technique acquires motion encoded snapshot images in which various forms of motion and confounders are entangled. First, we optimized the motion sensitivity for application in the human brain. Next, we isolated the heartbeat and respiration-related deformations, by introducing a linear model that fits the snapshot series to the recorded physiological information. As a result, we obtained maps of the physiological tissue deformation with 3mm isotropic spatial resolution. Heartbeat and respiration-induced volumetric strain were significantly different from zero in the basal ganglia (median (25-75% interquartile range): 0.85·10-3 (0.39·10-3-1.05·10-3), p = 0.0008 and -0.28·10-3 (-0.41·10-3-0.06·10-3), p = 0.047, respectively. Smaller volumetric strains were observed in the white matter of the centrum semi ovale (0.28·10-3 (0-0.59·10-3) and -0.06·10-3 (-0.17·10-3-0.20·10-3)), which was only significant for the heartbeat (p = 0.02 and p = 0.7, respectively). Furthermore, heartbeat-induced volumetric strain was about three times larger than respiration-induced volumetric strain. This technique opens a window on the driving forces of the human brain clearance system.
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22
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Adams AL, Viergever MA, Luijten PR, Zwanenburg JJM. Validating faster DENSE measurements of cardiac-induced brain tissue expansion as a potential tool for investigating cerebral microvascular pulsations. Neuroimage 2019; 208:116466. [PMID: 31843712 DOI: 10.1016/j.neuroimage.2019.116466] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 12/13/2019] [Indexed: 11/17/2022] Open
Abstract
Displacement Encoding with Stimulated Echoes (DENSE) has recently shown potential for measuring cardiac-induced cerebral volumetric strain in the human brain. As such, it may provide a powerful tool for investigating the cerebral small vessels. However, further development and validation are necessary. This study aims, first, to validate a retrospectively-gated implementation of the DENSE method for assessing brain tissue pulsations as a physiological marker, and second, to use the acquired measurements to explore intracranial volume dynamics. We acquired repeated measurements of cerebral volumetric strain in 8 healthy subjects, and internally validated these measurements by comparing them to spinal CSF stroke volumes obtained in the same scan session. Peak volumetric strain was found to be highly repeatable between scan sessions. First/second measured peak volumetric strains were: (6.4 ± 1.7)x10-4/(6.7 ± 1.6)x10-4 for whole brain, (9.5 ± 2.5)x10-4/(9.6 ± 2.4)x10-4 for grey matter, and (4.4 ± 1.7)x10-4/(4.1 ± 0.8)x10-4 for white matter. Grey matter showed significantly higher peak strain (p < 0.001) and earlier time-to-peak strain (p < 0.02) than white matter. An approximately linear relationship was found between CSF and brain tissue volume pulsations over the cardiac cycle (mean slope and R2 of 0.88 ± 0.23 and 0.89 ± 0.07, respectively). The close similarity between CSF and brain tissue volume pulsations implies limited contributions from large intracranial vessel pulsations, providing further evidence for venous compression as an additional mechanism for maintaining stable intracranial pressures over the cardiac cycle. Cerebral pulsatility showed consistent inter-subject peak values in healthy subjects, and was strongly correlated to CSF stroke volumes. These results strengthen the potential of brain tissue volumetric strain as a means for investigating the intracranial dynamics of the ageing brain in normal or diseased states.
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Affiliation(s)
- Ayodeji L Adams
- Department of Radiology, University Medical Center Utrecht, E 01.132, Heidelberglaan 100, 3584 CX, Utrecht, the Netherlands.
| | - Max A Viergever
- Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, the Netherlands.
| | - Peter R Luijten
- Department of Radiology, University Medical Center Utrecht, E 01.132, Heidelberglaan 100, 3584 CX, Utrecht, the Netherlands.
| | - Jaco J M Zwanenburg
- Department of Radiology, University Medical Center Utrecht, E 01.132, Heidelberglaan 100, 3584 CX, Utrecht, the Netherlands.
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23
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Hetzer S, Dittmann F, Bormann K, Hirsch S, Lipp A, Wang DJ, Braun J, Sack I. Hypercapnia increases brain viscoelasticity. J Cereb Blood Flow Metab 2019; 39:2445-2455. [PMID: 30182788 PMCID: PMC6893988 DOI: 10.1177/0271678x18799241] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Brain function, the brain's metabolic activity, cerebral blood flow (CBF), and intracranial pressure are intimately linked within the tightly autoregulated regime of intracranial physiology in which the role of tissue viscoelasticity remains elusive. We applied multifrequency magnetic resonance elastography (MRE) paired with CBF measurements in 14 healthy subjects exposed to 5-min carbon dioxide-enriched breathing air to induce cerebral vasodilatation by hypercapnia. Stiffness and viscosity as quantified by the magnitude and phase angle of the complex shear modulus, |G*| and ϕ, as well as CBF of the whole brain and 25 gray matter sub-regions were analyzed prior to, during, and after hypercapnia. In all subjects, whole-brain stiffness and viscosity increased due to hypercapnia by 3.3 ± 1.9% and 2.0 ± 1.1% which was accompanied by a CBF increase of 36 ± 15%. Post-hypercapnia, |G*| and ϕ reduced to normal values while CBF decreased by 13 ± 15% below baseline. Hypercapnia-induced viscosity changes correlated with CBF changes, whereas stiffness changes did not. The MRE-measured viscosity changes correlated with blood viscosity changes predicted by the Fåhræus-Lindqvist model and microvessel diameter changes from the literature. Our results suggest that brain viscoelastic properties are influenced by microvessel blood flow and blood viscosity: vasodilatation and increased blood viscosity due to hypercapnia result in an increase in MRE values related to viscosity.
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Affiliation(s)
- Stefan Hetzer
- Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Florian Dittmann
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Karl Bormann
- Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Sebastian Hirsch
- Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin, Berlin, Germany.,Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Axel Lipp
- Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Danny Jj Wang
- Laboratory of FMRI Technology, University of Southern California, Los Angeles, CA, USA
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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24
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Viscoelasticity of striatal brain areas reflects variations in body mass index of lean to overweight male adults. Brain Imaging Behav 2019; 14:2477-2487. [PMID: 31512097 DOI: 10.1007/s11682-019-00200-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although a variety of MRI studies investigated the link between body mass index (BMI) and parameters of neural gray matter (GM), the technique applied in most of these studies, voxel-based morphometry (VBM), focusses on the regional GM volume, a macroscopic tissue property. Thus, the studies were not able to exploit the BMI-related information contained in the GM microstructure although PET studies suggest that these factors are important. Here, we used cerebral MR Elastography (MRE) to characterize features of tissue microstructure by evaluating the propagation of shear waves applied to the skull and to assess local tissue viscoelasticity to test the link between this parameter and BMI in 22 lean to overweight males. Unlike the majority of existing MRE studies investigating neural viscoelasticity signals averaged across large brain regions, we used the viscoelasticity of individual voxels for our experiment. Our technique revealed a negative link between BMI and viscoelasticity of two areas of the striatal reward system, i.e., right putamen (t = -8.2; pFWE-corrected = 0.005) and left globus pallidus (t = -7.1; pFWE = 0.037) which was independent of GM volume at these coordinates. Finally, comparison of BMI models based on individual voxels vs. on signals averaged across brain atlas regions demonstrates that voxel-based models explain a significantly higher proportion of variance. Consequently, our findings show that cerebral MRE is suitable to identify medically relevant microstructural tissue properties. Using a voxel-wise analysis approach, we were able to utilize the high spatial resolution of MRE for mapping BMI-related information in the brain.
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25
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Viessmann O, Scheffler K, Bianciardi M, Wald LL, Polimeni JR. Dependence of resting-state fMRI fluctuation amplitudes on cerebral cortical orientation relative to the direction of B0 and anatomical axes. Neuroimage 2019; 196:337-350. [PMID: 31002965 PMCID: PMC6559854 DOI: 10.1016/j.neuroimage.2019.04.036] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 03/30/2019] [Accepted: 04/11/2019] [Indexed: 01/21/2023] Open
Abstract
Functional magnetic resonance imaging (fMRI) is now capable of sub-millimetre scale measurements over the entire human brain, however with such high resolutions each voxel is influenced by the local fine-scale details of the cerebral cortical vascular anatomy. The cortical vasculature is structured with the pial vessels lying tangentially along the grey matter surface, intracortical diving arterioles and ascending venules running perpendicularly to the surface, and a randomly oriented capillary network within the parenchyma. It is well-known that the amplitude of the blood-oxygenation level dependent (BOLD) signal emanating from a vessel depends on its orientation relative to the B0-field. Thus the vascular geometric hierarchy will impart an orientation dependence to the BOLD signal amplitudes and amplitude differences due to orientation differences constitute a bias for interpreting neuronal activity. Here, we demonstrate a clear effect of cortical orientation to B0 in the resting-state BOLD-fMRI amplitude (quantified as the coefficient of temporal signal variation) for 1.1 mm isotropic data at 7T and 2 mm isotropic at 3T. The maximum bias, i.e. the fluctuation amplitude difference between regions where cortex is perpendicular to vs. parallel to B0, is about +70% at the pial surface at 7T and +11% at 3T. The B0 orientation bias declines with cortical depth, becomes progressively smaller closer to the white matter surface, but then increases again to a local maximum within the white matter just beneath the cortical grey matter, suggesting a distinct tangential network of white matter vessels that also generate a BOLD orientation effect. We further found significant (negative) biases with the cortex orientation to the anterior-posterior anatomical axis of the head: a maximum negative bias of about -30% at the pial surface at 7T and about -13% at 3T. The amount of signal variance explained by the low frequency drift, motion and the respiratory cycle also showed a cortical orientation dependence; only the cardiac cycle induced signal variance was independent of cortical orientation, suggesting that the cardiac induced component of the image time-series fluctuations is not related to a significant change in susceptibility. Although these orientation effects represent a signal bias, and are likely to be a nuisance in high-resolution analyses, they may help characterize the vascular influences on candidate fMRI acquisitions and, thereby, may be exploited to improve the neuronal specificity of fMRI.
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Affiliation(s)
- Olivia Viessmann
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 149 13th St., Charlestown, Boston, MA 02129, USA.
| | - Klaus Scheffler
- Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 11, 72076 Tübingen, Germany.
| | - Marta Bianciardi
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 149 13th St., Charlestown, Boston, MA 02129, USA.
| | - Lawrence L Wald
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 149 13th St., Charlestown, Boston, MA 02129, USA; Harvard-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Cambridge, MA, USA.
| | - Jonathan R Polimeni
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, 149 13th St., Charlestown, Boston, MA 02129, USA; Harvard-Massachusetts Institute of Technology, Division of Health Sciences and Technology, Cambridge, MA, USA.
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26
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Barnhill E, Nikolova M, Ariyurek C, Dittmann F, Braun J, Sack I. Fast Robust Dejitter and Interslice Discontinuity Removal in MRI Phase Acquisitions: Application to Magnetic Resonance Elastography. IEEE TRANSACTIONS ON MEDICAL IMAGING 2019; 38:1578-1587. [PMID: 30703013 DOI: 10.1109/tmi.2019.2893369] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
MRI phase contrast imaging methods that assemble slice-wise acquisitions into volumes can contain interslice phase discontinuities (IPDs) over the course of the scan from sources, including unavoidable physiological activity. In magnetic resonance elastography (MRE), this can alter wavelength and tissue stiffness estimates, invalidating the analysis. We first model this behavior as jitter along the z-axis of the phase of 3D complex-valued wave volumes. A two-step image processing pipeline is then proposed that removes IPDs. First, constant slicewise phase shift is removed with a novel, non-convex dejittering algorithm. Then, regional physiological noise artifacts are removed with novel filtering of 3D wavelet coefficients. Calibration of two pipeline coefficients, the dejitter parameter α and the wavelet band high-pass coefficient ωc , was first performed on a finite-element method brain phantom. A comparative investigation was then performed, on a cohort of 48 brain acquisitions, of four approaches to IPDs: 1) the proposed method; 2) a "control" condition of neglect of IPDs; 3) an anisotropic wavelet-based method; and 4) a method of in-plane (2D) processing. The present method showed medians of [Formula: see text] Pa for a multifrequency wave inversion centered at 40 Hz which was within 6% of methods 3) and 4), while neglect produced [Formula: see text] estimates a mean of 17% lower. The proposed method reduced the value range of the cohort against methods 3) and 4) by 29% and 31%, respectively. Such reduction in variance enhances the ability of brain MRE to predict subtler physiological changes. Our theoretical approach further enables more powerful applications of fundamental findings in noise and denoising to MRE.
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27
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Bert RJ, Settipalle N, Tiwana E, Muddasani D, Nath R, Wellman B, Mihlon F, Negahdar M, Amini A, Boakye M. The relationships among spinal CSF flows, spinal cord geometry, and vascular correlations: evidence of intrathecal sources and sinks. Am J Physiol Regul Integr Comp Physiol 2019; 317:R470-R484. [PMID: 31242020 DOI: 10.1152/ajpregu.00101.2018] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We studied relationships of cerebral spinal fluid (CSF) pulsatile flow at cervical, thoracic, and lumbar levels using phase-contrast cine MRI (PCCMRI) to determine the following: 1) instantaneous and average net flows at cervical, thoracic, and lumbar levels, 2) stochastic correlations of CSF flow with major arterial supplies and major draining veins, and 3) whether adjustments of cord-flow curves-using cord cross-sectional areas, caudal lengths, and caudal volumes-would normalize flow curves from different levels. We scanned 15 healthy volunteers without anesthesia, ages 23-46 yr, using external, retrocardiac-gated, two-dimensional PCCMRI at 3T. Transverse scans of the subarachnoid space, arteries, and veins were acquired and analyzed at cervical, thoracic, and lumbar levels. Instantaneous CSF flow decreased craniocaudally along the full time course of a cardiac cycle. Downward net flow generally increased craniocaudally. During diastole, instantaneous CSF flow decreased proportionally to cross-sectional area, caudal residual length, and caudal residual volume of the cord. The proportionalities were less consistent during systole. CSF, internal carotid artery (ICA), vertebral artery, and lower aorta temporal correlations were highest in systole and decreased craniocaudally. CSF flow temporally correlated better with lower aorta flow than with the ICA at T7 and L2 during systole but not diastole. Inferior vena cava temporal correlation increased craniocaudally. We conclude that whereas instantaneous flow is attenuated cranial caudally, net downward flow, per cardiac cycle, increases caudally, becoming statistically significant at T7 and below the conus medullaris. We can explain the results with the assumption of cord CSF production and peripheral-dominated CSF absorption.
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Affiliation(s)
- Robert J Bert
- Department of Radiology, University of Louisville, Louisville, Kentucky
| | - Neesha Settipalle
- Department of Internal Medicine, St. Michael's Medical Center, Newark, New Jersey
| | - Emily Tiwana
- Department of Radiology, University of Louisville, Louisville, Kentucky
| | - Dheeraj Muddasani
- Department of Radiology, University of Louisville, Louisville, Kentucky
| | - Ruponti Nath
- Speed School of Electrical and Computer Engineering, University of Louisville, Louisville, Kentucky
| | - Brandon Wellman
- Department of Radiology, University of Louisville, Louisville, Kentucky
| | - Frank Mihlon
- Hampton Roads Radiology Associates, PA, Norfolk, Virginia
| | | | - Amir Amini
- Speed School of Electrical and Computer Engineering, University of Louisville, Louisville, Kentucky
| | - Maxwell Boakye
- Department of Neurosurgery, University of Louisville, Louisville, Kentucky
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28
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Solamen LM, Gordon-Wylie SW, McGarry MD, Weaver JB, Paulsen KD. Phantom evaluations of low frequency MR elastography. ACTA ACUST UNITED AC 2019; 64:065010. [DOI: 10.1088/1361-6560/ab0290] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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29
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Huang L, Korhonen RK, Turunen MJ, Finnilä MAJ. Experimental mechanical strain measurement of tissues. PeerJ 2019; 7:e6545. [PMID: 30867989 PMCID: PMC6409087 DOI: 10.7717/peerj.6545] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 01/31/2019] [Indexed: 12/22/2022] Open
Abstract
Strain, an important biomechanical factor, occurs at different scales from molecules and cells to tissues and organs in physiological conditions. Under mechanical strain, the strength of tissues and their micro- and nanocomponents, the structure, proliferation, differentiation and apoptosis of cells and even the cytokines expressed by cells probably shift. Thus, the measurement of mechanical strain (i.e., relative displacement or deformation) is critical to understand functional changes in tissues, and to elucidate basic relationships between mechanical loading and tissue response. In the last decades, a great number of methods have been developed and applied to measure the deformations and mechanical strains in tissues comprising bone, tendon, ligament, muscle and brain as well as blood vessels. In this article, we have reviewed the mechanical strain measurement from six aspects: electro-based, light-based, ultrasound-based, magnetic resonance-based and computed tomography-based techniques, and the texture correlation-based image processing method. The review may help solving the problems of experimental and mechanical strain measurement of tissues under different measurement environments.
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Affiliation(s)
- Lingwei Huang
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Rami K Korhonen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikael J Turunen
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland
| | - Mikko A J Finnilä
- Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.,Research Unit of Medical Imaging, Physics and Technology, University of Oulu, Oulu, Finland.,Medical Research Center Oulu, Oulu University Hospital, Oulu, Finland
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30
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Rivera-Rivera LA, Johnson KM, Turski PA, Wieben O, Schubert T. Measurement of microvascular cerebral blood volume changes over the cardiac cycle with ferumoxytol-enhanced T 2 * MRI. Magn Reson Med 2019; 81:3588-3598. [PMID: 30756424 DOI: 10.1002/mrm.27670] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 12/28/2018] [Accepted: 01/04/2019] [Indexed: 12/24/2022]
Abstract
PURPOSE This feasibility study investigates the non-invasive measurement of microvascular cerebral blood volume (BV) changes over the cardiac cycle using cardiac-gated, ferumoxytol-enhanced T 2 ∗ MRI. METHODS Institutional review board approval was obtained and all subjects provided written informed consent. Cardiac gated MR scans were prospectively acquired on a 3.0T scanner in 22 healthy subjects using T 2 ∗ -weighted sequences with 2D-EPI and 3D spiral trajectories. Images were collected before and after the intravenous administration of 2 doses of ferumoxytol (1 mg FE/kg and 4 mg FE/kg). Cardiac cycle-induced R 2 ∗ (1/ T 2 ∗ ) changes (Δ R 2 ∗ ) and BV changes (ΔBV) throughout the cardiac cycle in gray matter (GM) and white matter (WM) were quantified and differences assessed using ANOVA followed by post hoc analysis. RESULTS Δ R 2 ∗ was found to increase in a dose-dependent fashion. A significantly larger increase was observed in GM compared to WM in both 2D and 3D acquisitions (P < 0.050). In addition, Δ R 2 ∗ increased significantly (P < 0.001) post versus pre-contrast injection in GM in both T 2 ∗ MRI acquisitions. Mean GM Δ R 2 ∗ derived from 2D-EPI images was 0.14 ± 0.06 s-1 pre-contrast and 0.33 ± 0.13 s-1 after 5 mg FE/kg. In WM, Δ R 2 ∗ was 0.19 ± 0.06 s-1 pre-contrast, and 0.23 ± 0.06 s-1 after 5 mg FE/kg. The fractional changes in BV throughout the cardiac cycle were 0.031 ± 0.019% in GM and 0.011 ± 0.008% in WM (P < 0.001) after 5 mg FE/kg. CONCLUSION Cardiac-gated, ferumoxytol-enhanced T 2 ∗ MRI enables characterization of microvascular BV changes throughout the cardiac cycle in GM and WM tissue of healthy subjects.
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Affiliation(s)
- Leonardo A Rivera-Rivera
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Kevin M Johnson
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Patrick A Turski
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Oliver Wieben
- Department of Medical Physics, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Tilman Schubert
- Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin.,Department of Radiology and Nuclear Medicine, Basel University Hospital, Petersgraben 4, 4031, Basel, Switzerland
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31
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Adams AL, Kuijf HJ, Viergever MA, Luijten PR, Zwanenburg JJ. Quantifying cardiac-induced brain tissue expansion using DENSE. NMR IN BIOMEDICINE 2019; 32:e4050. [PMID: 30575151 PMCID: PMC6519010 DOI: 10.1002/nbm.4050] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 10/16/2018] [Accepted: 11/12/2018] [Indexed: 06/09/2023]
Abstract
Brain tissue undergoes viscoelastic deformation and volumetric strain as it expands over the cardiac cycle due to blood volume changes within the underlying microvasculature. Volumetric strain measurements may therefore provide insights into small vessel function and tissue viscoelastic properties. Displacement encoding via stimulated echoes (DENSE) is an MRI technique that can quantify the submillimetre displacements associated with brain tissue motion. Despite previous studies reporting brain tissue displacements using DENSE and other MRI techniques, a complete picture of brain tissue volumetric strain over the cardiac cycle has not yet been obtained. To address this need we implemented 3D cine-DENSE at 7 T and 3 T to investigate the feasibility of measuring cardiac-induced volumetric strain as a marker for small vessel blood volume changes. Volumetric strain over the entire cardiac cycle was computed for the whole brain and for grey and white matter tissue separately in six healthy human subjects. Signal-to-noise ratio (SNR) measurements were used to determine the voxel-wise volumetric strain noise. Mean peak whole brain volumetric strain at 7 T (mean ± SD) was (4.5 ± 1.0) × 10-4 (corresponding to a volume expansion of 0.48 ± 0.1 mL), which is in agreement with literature values for cerebrospinal fluid that is displaced into the spinal canal to maintain a stable intracranial pressure. The peak volumetric strain ratio of grey to white matter was 4.4 ± 2.8, reflecting blood volume and tissue stiffness differences between these tissue types. The mean peak volumetric strains of grey and white matter tissue were found to be significantly different (p < 0.001). The mean SNR at 7 T and 3 T of the DENSE measurements was 22.0 ± 7.3 and 7.0 ± 2.8 respectively, which currently limits a voxel-wise strain analysis at both field strengths. We demonstrate that tissue specific quantification of volumetric strain is feasible with DENSE. This metric holds potential for studying blood volume pulsations in the ageing brain in healthy and diseased states.
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Affiliation(s)
- Ayodeji L. Adams
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Hugo J. Kuijf
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Max A. Viergever
- Image Sciences InstituteUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Peter R. Luijten
- Department of RadiologyUniversity Medical Center UtrechtUtrechtThe Netherlands
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32
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Tzschätzsch H, Kreft B, Schrank F, Bergs J, Braun J, Sack I. In vivo time-harmonic ultrasound elastography of the human brain detects acute cerebral stiffness changes induced by intracranial pressure variations. Sci Rep 2018; 8:17888. [PMID: 30559367 PMCID: PMC6297160 DOI: 10.1038/s41598-018-36191-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Accepted: 11/15/2018] [Indexed: 12/19/2022] Open
Abstract
Cerebral stiffness (CS) reflects the biophysical environment in which neurons grow and function. While long-term CS changes can occur in the course of chronic neurological disorders and aging, little is known about acute variations of CS induced by intracranial pressure variations. Current gold standard methods for CS and intracranial pressure such as magnetic resonance elastography and direct pressure recordings are either expensive and slow or invasive. The study objective was to develop a real-time method for in vivo CS measurement and to demonstrate its sensitivity to physiological aging and intracranial pressure variations induced by the Valsalva maneuver in healthy volunteers. We used trans-temporal ultrasound time-harmonic elastography (THE) with external shear-wave stimulation by continuous and superimposed vibrations in the frequency range from 27 to 56 Hz. Multifrequency wave inversion generated maps of shear wave speed (SWS) as a surrogate maker of CS. On average, cerebral SWS was 1.56 ± 0.08 m/s with a tendency to reduce with age (R = -0.76, p < 0.0001) while Valsalva maneuver induced an immediate stiffening of the brain as reflected by a 10.8 ± 2.5% increase (p < 0.0001) in SWS. Our results suggest that CS is tightly linked to intracranial pressure and might be used in the future as non-invasive surrogate marker for intracranial pressure, which otherwise requires invasive measurements.
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Affiliation(s)
- Heiko Tzschätzsch
- Department of Radiology, , Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Bernhard Kreft
- Department of Radiology, , Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Felix Schrank
- Department of Radiology, , Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Judith Bergs
- Department of Radiology, , Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, , Charité - Universitätsmedizin Berlin, Berlin, Germany.
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33
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Bertalan G, Guo J, Tzschätzsch H, Klein C, Barnhill E, Sack I, Braun J. Fast tomoelastography of the mouse brain by multifrequency single‐shot MR elastography. Magn Reson Med 2018; 81:2676-2687. [DOI: 10.1002/mrm.27586] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Revised: 10/04/2018] [Accepted: 10/07/2018] [Indexed: 12/13/2022]
Affiliation(s)
- Gergely Bertalan
- Department of Radiology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Jing Guo
- Department of Radiology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Heiko Tzschätzsch
- Department of Radiology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Charlotte Klein
- Department of Neurology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Eric Barnhill
- Department of Radiology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Ingolf Sack
- Department of Radiology Charité–Universitätsmedizin Berlin, Campus Charité MitteBerlin Germany
| | - Jürgen Braun
- Institute of Medical Informatics Charité–Universitätsmedizin Berlin, Campus Benjamin FranklinBerlin Germany
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34
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Guenthner C, Kozerke S. Encoding and readout strategies in magnetic resonance elastography. NMR IN BIOMEDICINE 2018; 31:e3919. [PMID: 29806865 DOI: 10.1002/nbm.3919] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2017] [Revised: 12/15/2017] [Accepted: 02/15/2018] [Indexed: 06/08/2023]
Abstract
Magnetic resonance elastography (MRE) has evolved significantly since its inception. Advances in motion-encoding gradient design and readout strategies have led to improved encoding and signal-to-noise ratio (SNR) efficiencies, which in turn allow for higher spatial resolution, increased coverage, and/or shorter scan times. The purpose of this review is to summarize MRE wave-encoding and readout approaches in a unified mathematical framework to allow for a comparative assessment of encoding and SNR efficiency of the various methods available. Besides standard full- and fractional-wave-encoding approaches, advanced techniques including flow compensation, sample interval modulation and multi-shot encoding are considered. Signal readout using fast k-space trajectories, reduced field of view, multi-slice, and undersampling techniques are summarized and put into perspective. The review is concluded with a foray into displacement and diffusion encoding as alternative and/or complementary techniques.
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Affiliation(s)
- Christian Guenthner
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
| | - Sebastian Kozerke
- Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland
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Yin Z, Romano AJ, Manduca A, Ehman RL, Huston J. Stiffness and Beyond: What MR Elastography Can Tell Us About Brain Structure and Function Under Physiologic and Pathologic Conditions. Top Magn Reson Imaging 2018; 27:305-318. [PMID: 30289827 PMCID: PMC6176744 DOI: 10.1097/rmr.0000000000000178] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Brain magnetic resonance elastography (MRE) was developed on the basis of a desire to "palpate by imaging" and is becoming a powerful tool in the investigation of neurophysiological and neuropathological states. Measurements are acquired with a specialized MR phase-contrast pulse sequence that can detect tissue motion in response to an applied external or internal excitation. The tissue viscoelasticity is then reconstructed from the measured displacement. Quantitative characterization of brain viscoelastic behaviors provides us an insight into the brain structure and function by assessing the mechanical rigidity, viscosity, friction, and connectivity of brain tissues. Changes in these features are associated with inflammation, demyelination, and neurodegeneration that contribute to brain disease onset and progression. Here, we review the basic principles and limitations of brain MRE and summarize its current neuroanatomical studies and clinical applications to the most common neurosurgical and neurodegenerative disorders, including intracranial tumors, dementia, multiple sclerosis, amyotrophic lateral sclerosis, and traumatic brain injury. Going forward, further improvement in acquisition techniques, stable inverse reconstruction algorithms, and advanced numerical, physical, and preclinical validation models is needed to increase the utility of brain MRE in both research and clinical applications.
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Affiliation(s)
- Ziying Yin
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN
| | | | - Armando Manduca
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN
- Departments of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, Rochester, MN
| | - Richard L. Ehman
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN
| | - John Huston
- Department of Radiology, Mayo Clinic College of Medicine, Rochester, MN
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Abstract
The mechanical properties of soft tissues are closely associated with a variety of diseases. This motivates the development of elastography techniques in which tissue mechanical properties are quantitatively estimated through imaging. Magnetic resonance elastography (MRE) is a noninvasive phase-contrast MR technique wherein shear modulus of soft tissue can be spatially and temporally estimated. MRE has recently received significant attention due to its capability in noninvasively estimating tissue mechanical properties, which can offer considerable diagnostic potential. In this work, recent technology advances of MRE, its future clinical applications, and the related limitations will be discussed.
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Affiliation(s)
- Huiming Dong
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
| | - Richard D. White
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
- Department of Internal Medicine-Division of Cardiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
| | - Arunark Kolipaka
- Department of Radiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
- Department of Biomedical Engineering, The Ohio State University, Columbus, OH, 43210, USA
- Department of Internal Medicine-Division of Cardiology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA
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Progressive supranuclear palsy and idiopathic Parkinson’s disease are associated with local reduction of in vivo brain viscoelasticity. Eur Radiol 2018; 28:3347-3354. [DOI: 10.1007/s00330-017-5269-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Revised: 11/27/2017] [Accepted: 12/20/2017] [Indexed: 10/18/2022]
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Hetzer S, Birr P, Fehlner A, Hirsch S, Dittmann F, Barnhill E, Braun J, Sack I. Perfusion alters stiffness of deep gray matter. J Cereb Blood Flow Metab 2018; 38:116-125. [PMID: 28151092 PMCID: PMC5757437 DOI: 10.1177/0271678x17691530] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Viscoelastic properties of the brain reflect tissue architecture at multiple length scales. However, little is known about the relation between vital tissue functions, such as perfusion, and the macroscopic mechanical properties of cerebral tissue. In this study, arterial spin labelling is paired with magnetic resonance elastography to investigate the relationship between tissue stiffness and cerebral blood flow (CBF) in the in vivo human brain. The viscoelastic modulus, | G*|, and CBF were studied in deep gray matter (DGM) of 14 healthy male volunteers in the following sub-regions: putamen, nucleus accumbens, hippocampus, thalamus, globus pallidus, and amygdala. CBF was further normalized by vessel area data to obtain the flux rate q which is proportional to the perfusion pressure gradient. The striatum (represented by putamen and nucleus accumbens) was distinct from the other DGM regions by displaying markedly higher stiffness and perfusion values. q was a predictive marker for DGM stiffness as analyzed by linear regression | G*| = q·(4.2 ± 0.6)kPa·s + (0.80 ± 0.06)kPa ( R2 = 0.92, P = 0.006). These results suggest a high sensitivity of MRE in DGM to perfusion pressure. The distinct mechano-vascular properties of striatum tissue, as compared to the rest of DGM, may reflect elevated perfusion pressure, which could explain the well-known susceptibility of the putamen to hemorrhages.
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Affiliation(s)
- Stefan Hetzer
- 1 Berlin Center for Advanced Neuroimaging, Charité - Universitätsmedizin Berlin, Berlin, Germany.,2 Bernstein Center for Computational Neuroscience, Berlin, Germany
| | - Patric Birr
- 3 Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Andreas Fehlner
- 3 Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Hirsch
- 4 Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Florian Dittmann
- 3 Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Eric Barnhill
- 3 Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jürgen Braun
- 4 Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- 3 Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Zwanenburg JJM, van Osch MJP. Targeting Cerebral Small Vessel Disease With MRI. Stroke 2017; 48:3175-3182. [PMID: 28970280 DOI: 10.1161/strokeaha.117.016996] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/28/2017] [Accepted: 09/05/2017] [Indexed: 11/16/2022]
Affiliation(s)
- Jaco J M Zwanenburg
- From the Deptartment of Radiology, University Medical Center Utrecht, the Netherlands (J.J.M.Z.); and Department of Radiology, Leiden University Medical Center, the Netherlands (M.J.P.v.O.).
| | - Matthias J P van Osch
- From the Deptartment of Radiology, University Medical Center Utrecht, the Netherlands (J.J.M.Z.); and Department of Radiology, Leiden University Medical Center, the Netherlands (M.J.P.v.O.)
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40
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Honarvar M, Sahebjavaher RS, Rohling R, Salcudean SE. A Comparison of Finite Element-Based Inversion Algorithms, Local Frequency Estimation, and Direct Inversion Approach Used in MRE. IEEE TRANSACTIONS ON MEDICAL IMAGING 2017; 36:1686-1698. [PMID: 28333623 DOI: 10.1109/tmi.2017.2686388] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In quantitative elastography, maps of the mechanical properties of soft tissue, or elastograms, are calculated from the measured displacement data by solving an inverse problem. The model assumptions have a significant effect on elastograms. Motivated by the high sensitivity of imaging results to the model assumptions for in vivo magnetic resonance elastography of the prostate, we compared elastograms obtained with four different methods. Two finite-element method (FEM)-based methods developed by our group were compared with two other commonly used methods, local frequency estimator (LFE) and curl-based direct inversion (c-DI). All the methods assume a linear isotropic elastic model, but the methods vary in their assumptions, such as local homogeneity or incompressibility, and in the specific approach used. We report results using simulations, phantom, and ex vivo and in vivo data. The simulation and phantom studies show, for regions with an inclusion, that the contrast to noise ratio (CNR) for the FEM methods is about three to five times higher than the CNR for the LFE and c-DI and the rms error is about half. The LFE method produces very smooth results (i.e., low CNR) and is fast. c-DI is faster than the FEM methods but it is only accurate in areas where elasticity variations are small. The artifacts resulting from the homogeneity assumption in c-DI is detrimental in regions with large variations. The ex vivo and in vivo results also show similar trends as the simulation and phantom studies. The c-FEM method is more sensitive to noise compared with the mixed-FEM due to higher orders derivatives. This is especially evident at lower frequencies, where the wave curvature is smaller and it is more prone to such error, causing a discrepancy in the absolute values between the mixed-FEM and c-FEM in our in vivo results. In general, the proposed FEMs use fewer simplifying assumptions and outperform the other methods but they are computationally more expensive.
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Arani A, Min HK, Fattahi N, Wetjen NM, Trzasko JD, Manduca A, Jack CR, Lee KH, Ehman RL, Huston J. Acute pressure changes in the brain are correlated with MR elastography stiffness measurements: initial feasibility in an in vivo large animal model. Magn Reson Med 2017; 79:1043-1051. [PMID: 28488326 PMCID: PMC5811891 DOI: 10.1002/mrm.26738] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Revised: 03/08/2017] [Accepted: 04/05/2017] [Indexed: 11/08/2022]
Abstract
PURPOSE The homeostasis of intracranial pressure (ICP) is of paramount importance for maintaining normal brain function. A noninvasive technique capable of making direct measurements of ICP currently does not exist. MR elastography (MRE) is capable of noninvasively measuring brain tissue stiffness in vivo, and may act as a surrogate to measure ICP. The objective of this study was to investigate the impact of changing ICP on brain stiffness using MRE in a swine model. METHODS Baseline MRE measurements were obtained, and then catheters were surgically placed into the left and right lateral ventricles of three animals. ICP was systematically increased over the range of 0 to 55 millimeters mercury (mmHg), and stiffness measurements were made using brain MRE at vibration frequencies of 60 hertz (Hz), 90 Hz, 120 Hz, and 150 Hz. RESULTS A significant linear correlation between stiffness and ICP in the cross-subject comparison was observed for all tested vibrational frequencies (P ≤ 0.01). The 120 Hz (0.030 ± 0.004 kilopascal (kPa)/mmHg, P < 0.0001) and 150 Hz (0.031 ± 0.008 kPa/mmHg, P = 0.01) vibrational frequencies had nearly identical slopes, which were approximately two- to three-fold higher than the 90 Hz (0.017 ± 0.002 kPa/mmHg, P < 0.0001) and 60 Hz (0.009 ± 0.002 kPa/mmHg, P = 0.001) slopes, respectively. CONCLUSION In this study, MRE demonstrated the potential for noninvasive measurement of changes in ICP. Magn Reson Med 79:1043-1051, 2018. © 2017 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
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Affiliation(s)
- Arvin Arani
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Hoon-Ki Min
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA.,Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA
| | - Nikoo Fattahi
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | | | | | - Armando Manduca
- Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota, USA
| | - Clifford R Jack
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - Kendall H Lee
- Department of Neurologic Surgery, Mayo Clinic, Rochester, Minnesota, USA
| | - Richard L Ehman
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
| | - John Huston
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, USA
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42
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Grasland-Mongrain P, Lu Y, Lesage F, Catheline S, Cloutier G. Generation of Shear Waves by Laser in Soft Media in the Ablative and Thermoelastic Regimes. APPLIED PHYSICS LETTERS 2016; 109:2219011-2219015. [PMID: 28090117 PMCID: PMC5226822 DOI: 10.1063/1.4968538] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
This article describes the generation of elastic shear waves in a soft medium using a laser beam. Our experiments show two different regimes depending on laser energy. Physical modeling of the underlying phenomena reveals a thermoelastic regime caused by a local dilatation resulting from temperature increase, and an ablative regime caused by a partial vaporization of the medium by the laser. Computed theoretical displacements are close to experimental measurements. A numerical study based on the physical modeling gives propagation patterns comparable to those generated experimentally. These results provide a physical basis for the feasibility of a shear wave elastography technique (a technique which measures a soft solid stiffness from shear wave propagation) by using a laser beam.
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Affiliation(s)
- Pol Grasland-Mongrain
- Laboratory of Biorheology and Medical Ultrasonics, Montreal Hospital Research Center, Montreal (QC), H1X0A9, Canada
| | - Yuankang Lu
- Laboratory of Biorheology and Medical Ultrasonics, Montreal Hospital Research Center, Montreal (QC), H1X0A9, Canada; Departement of Electrical Engineering, École Polytechnique of Montreal, Montreal (QC), H3C3A7, Canada
| | - Frederic Lesage
- Departement of Electrical Engineering, École Polytechnique of Montreal, Montreal (QC), H3C3A7, Canada; Institute of Biomedical Engineering, École Polytechnique and University of Montreal, Montreal (QC), H3T1J4, Canada
| | - Stefan Catheline
- Laboratory of Therapeutic Applications of Ultrasound, Inserm u1032, Inserm, Lyon, F-69003, France
| | - Guy Cloutier
- Laboratory of Biorheology and Medical Ultrasonics, Montreal Hospital Research Center, Montreal (QC), H1X0A9, Canada; Institute of Biomedical Engineering, École Polytechnique and University of Montreal, Montreal (QC), H3T1J4, Canada; Departement of Radiology, Radio-oncology and Nuclear Medicine, University of Montreal, Montreal (QC), H3C3J7, Canada
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43
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Multifrequency magnetic resonance elastography of the brain reveals tissue degeneration in neuromyelitis optica spectrum disorder. Eur Radiol 2016; 27:2206-2215. [DOI: 10.1007/s00330-016-4561-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Revised: 08/01/2016] [Accepted: 08/11/2016] [Indexed: 10/21/2022]
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44
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Grasland-Mongrain P, Miller-Jolicoeur E, Tang A, Catheline S, Cloutier G. Contactless remote induction of shear waves in soft tissues using a transcranial magnetic stimulation device. Phys Med Biol 2016; 61:2582-93. [PMID: 26952900 DOI: 10.1088/0031-9155/61/6/2582] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
This study presents the first observation of shear waves induced remotely within soft tissues. It was performed through the combination of a transcranial magnetic stimulation device and a permanent magnet. A physical model based on Maxwell and Navier equations was developed. Experiments were performed on a cryogel phantom and a chicken breast sample. Using an ultrafast ultrasound scanner, shear waves of respective amplitudes of 5 and 0.5 μm were observed. Experimental and numerical results were in good agreement. This study constitutes the framework of an alternative shear wave elastography method.
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Affiliation(s)
- Pol Grasland-Mongrain
- Laboratory of Biorheology and Medical Ultrasonics, Research Center of the University of Montreal Hospital (CRCHUM), Montreal, QC, Canada
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45
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Fehlner A, Behrens JR, Streitberger KJ, Papazoglou S, Braun J, Bellmann-Strobl J, Ruprecht K, Paul F, Würfel J, Sack I. Higher-resolution MR elastography reveals early mechanical signatures of neuroinflammation in patients with clinically isolated syndrome. J Magn Reson Imaging 2015; 44:51-8. [PMID: 26714969 DOI: 10.1002/jmri.25129] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 12/01/2015] [Indexed: 12/15/2022] Open
Abstract
PURPOSE To assess if higher-resolution magnetic resonance elastography (MRE) is a technique that can measure the in vivo mechanical properties of brain tissue and is sensitive to early signatures of brain tissue degradation in patients with clinically isolated syndrome (CIS). MATERIALS AND METHODS Seventeen patients with CIS and 33 controls were investigated by MRE with a 3T MRI scanner. Full-wave field data were acquired at seven drive frequencies from 30 to 60 Hz. The spatially resolved higher-resolution maps of magnitude |G*| and phase angle φ of the complex-valued shear modulus were obtained in addition to springpot model parameters. These parameters were spatially averaged in white matter (WM) and whole-brain regions and correlated with clinical and radiological parameters. RESULTS Spatially resolved MRE revealed that CIS reduced WM viscoelasticity, independent of imaging markers of multiple sclerosis and clinical scores. |G*| was reduced by 14% in CIS (1.4 ± 0.2 kPa vs. 1.7 ± 0.2 kPa, P < 0.001, 95% confidence interval [CI] [-0.4, -0.1] kPa), while φ (0.66 ± 0.04 vs. 0.67 ± 0.04, P = 0.65, 95% CI [-0.04, 0.02]) remained unaltered. Springpot-based shear elasticity showed only a trend of CIS-related reduction (3.4 ± 0.5 kPa vs. 3.7 ± 0.5 kPa, P = 0.06, 95% CI [-0.6, 0.02] kPa) in the whole brain. CONCLUSION We demonstrate that CIS leads to significantly reduced elasticity of brain parenchyma, raising the prospect of using MRE as an imaging marker for subtle and diffuse tissue damage in neuroinflammatory diseases. J. Magn. Reson. Imaging 2016;44:51-58.
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Affiliation(s)
- Andreas Fehlner
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Janina Ruth Behrens
- Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Kaspar-Josche Streitberger
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Sebastian Papazoglou
- NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Judith Bellmann-Strobl
- NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Klemens Ruprecht
- Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Friedemann Paul
- NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Clinical and Experimental Multiple Sclerosis Research Center, Department of Neurology, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Experimental and Clinical Research Center, Charité - Universitätsmedizin Berlin, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Jens Würfel
- NeuroCure Clinical Research Center, Charité - Universitätsmedizin Berlin, Berlin, Germany.,Medical Image Analysis Center Basel, Switzerland
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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Fehlner A, Papazoglou S, McGarry MD, Paulsen KD, Guo J, Streitberger KJ, Hirsch S, Braun J, Sack I. Cerebral multifrequency MR elastography by remote excitation of intracranial shear waves. NMR IN BIOMEDICINE 2015; 28:1426-32. [PMID: 26373228 PMCID: PMC4962702 DOI: 10.1002/nbm.3388] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 05/05/2023]
Abstract
The aim of this study was to introduce remote wave excitation for high-resolution cerebral multifrequency MR elastography (mMRE). mMRE of 25-45-Hz drive frequencies by head rocker stimulation was compared with mMRE by remote wave excitation based on a thorax mat in 12 healthy volunteers. Maps of the magnitude |G*| and phase φ of the complex shear modulus were reconstructed using multifrequency dual elasto-visco (MDEV) inversion. After the scan, the subjects and three operators assessed the comfort and convenience of cerebral mMRE using two methods of stimulating the brain. Images were acquired in a coronal view in order to identify anatomical regions along the spinothalamic pathway. In mMRE by remote actuation, all subjects and operators appreciated an increased comfort and simplified procedural set-up. The resulting strain amplitudes in the brain were sufficiently large to analyze using MDEV inversion, and yielded high-resolution viscoelasticity maps which revealed specific anatomical details of brain mechanical properties: |G*| was lowest in the pons (0.97 ± 0.08 kPa) and decreased within the corticospinal tract in the caudal-cranial direction from the crus cerebri (1.64 ± 0.26 kPa) to the capsula interna (1.29 ± 0.14 kPa). By avoiding onerous mechanical stimulation of the head, remote excitation of intracranial shear waves can be used to measure viscoelastic parameters of the brain with high spatial resolution. Therewith, the new mMRE method is suitable for neuroradiological examinations in the clinic.
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Affiliation(s)
- Andreas Fehlner
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | | | | | - Keith D Paulsen
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
| | - Jing Guo
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | | | - Sebastian Hirsch
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité - Universitätsmedizin Berlin, Berlin, Germany
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47
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Dittmann F, Hirsch S, Tzschätzsch H, Guo J, Braun J, Sack I. In vivo wideband multifrequency MR elastography of the human brain and liver. Magn Reson Med 2015; 76:1116-26. [DOI: 10.1002/mrm.26006] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2015] [Revised: 08/25/2015] [Accepted: 09/12/2015] [Indexed: 01/19/2023]
Affiliation(s)
- Florian Dittmann
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Sebastian Hirsch
- Institute of Medical Informatics; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Heiko Tzschätzsch
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Jing Guo
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Jürgen Braun
- Institute of Medical Informatics; Charité - Universitätsmedizin Berlin; Berlin Germany
| | - Ingolf Sack
- Department of Radiology; Charité - Universitätsmedizin Berlin; Berlin Germany
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48
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McGrath DM, Ravikumar N, Wilkinson ID, Frangi AF, Taylor ZA. Magnetic resonance elastography of the brain: An in silico study to determine the influence of cranial anatomy. Magn Reson Med 2015; 76:645-62. [PMID: 26417988 DOI: 10.1002/mrm.25881] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 07/11/2015] [Accepted: 07/19/2015] [Indexed: 12/15/2022]
Abstract
PURPOSE Magnetic resonance elastography (MRE) of the brain has demonstrated potential as a biomarker of neurodegenerative disease such as dementia but requires further evaluation. Cranial anatomical features such as the falx cerebri and tentorium cerebelli membranes may influence MRE measurements through wave reflection and interference and tissue heterogeneity at their boundaries. We sought to determine the influence of these effects via simulation. METHODS MRE-associated mechanical stimulation of the brain was simulated using steady state harmonic finite element analysis. Simulations of geometrical models and anthropomorphic brain models derived from anatomical MRI data of healthy individuals were compared. Constitutive parameters were taken from MRE measurements for healthy brain. Viscoelastic moduli were reconstructed from the simulated displacement fields and compared with ground truth. RESULTS Interference patterns from reflections and heterogeneity resulted in artifacts in the reconstructions of viscoelastic moduli. Artifacts typically occurred in the vicinity of boundaries between different tissues within the cranium, with a magnitude of 10%-20%. CONCLUSION Given that MRE studies for neurodegenerative disease have reported only marginal variations in brain elasticity between controls and patients (e.g., 7% for Alzheimer's disease), the predicted errors are a potential confound to the development of MRE as a biomarker of dementia and other neurodegenerative diseases. Magn Reson Med 76:645-662, 2016. © 2015 Wiley Periodicals, Inc.
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Affiliation(s)
- Deirdre M McGrath
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.,Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, The University of Sheffield, Sheffield, UK
| | - Nishant Ravikumar
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, The University of Sheffield, Sheffield, UK
| | - Iain D Wilkinson
- Academic Unit of Radiology, Faculty of Medicine, Dentistry & Health, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
| | - Alejandro F Frangi
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Electronic and Electrical Engineering, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
| | - Zeike A Taylor
- CISTIB Centre for Computational Imaging & Simulation Technologies in Biomedicine, Department of Mechanical Engineering, The University of Sheffield, Sheffield, UK.,INSIGNEO Institute for In Silico Medicine, The University of Sheffield, Sheffield, UK
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Guo J, Hirsch S, Scheel M, Braun J, Sack I. Three-parameter shear wave inversion in MR elastography of incompressible transverse isotropic media: Application to in vivo lower leg muscles. Magn Reson Med 2015; 75:1537-45. [PMID: 25988407 DOI: 10.1002/mrm.25740] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 03/12/2015] [Accepted: 03/24/2015] [Indexed: 12/25/2022]
Abstract
PURPOSE To develop and demonstrate MR elastography (MRE) for the measurement of three independent viscoelastic constants of skeletal muscle according to the theory of linear elasticity of incompressible materials with transverse isotropy (TI). METHODS Three-dimensional multifrequency MRE was applied to soleus, gastrocnemius, and tibialis anterior muscles in 10 healthy volunteers. The rotational wave fields were solved for complex-valued viscoelastic parameters μ12, μ13, and E3 corresponding to two shear moduli (within the planes of isotropy and symmetry of TI materials) and Young's modulus (along the principal fiber axis). RESULTS Anisotropy was represented by the inequality μ12 < μ13 < 1/3E3 considering storage and loss properties of the soleus and gastrocnemius muscles, whereas storage shear moduli of tibialis were indistinguishable. Storage moduli were: 1.06 ± 0.12, 1.33 ± 0.10, 6.92 ± 0.95 kPa (soleus); 0.90 ± 0.11, 1.30 ± 0.15, 8.22 ± 1.37 kPa (gastrocnemius); 1.26 ± 0.16, 1.27 ± 0.11, 9.29 ± 1.42 kPa (tibialis), for μ12, μ13, and E3, respectively. The muscles were different in their μ12 and E3 values, whereas μ13 was less sensitive to the muscle type. Leg differences were observed in the soleus and gastrocnemius muscles. CONCLUSION Recovery of the full elasticity tensor in incompressible TI materials is feasible by three-dimensional inversion of the time-harmonic shear wave equation. The method is potentially useful for the clinical evaluation of skeletal muscle anisotropy.
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Affiliation(s)
- Jing Guo
- Department of Radiology, Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany
| | - Sebastian Hirsch
- Department of Radiology, Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany
| | - Michael Scheel
- Department of Radiology, Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany
| | - Jürgen Braun
- Institute of Medical Informatics, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany
| | - Ingolf Sack
- Department of Radiology, Charité-Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany
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Klatt D, Johnson CL, Magin RL. Simultaneous, multidirectional acquisition of displacement fields in magnetic resonance elastography of the in vivo human brain. J Magn Reson Imaging 2014; 42:297-304. [PMID: 25425147 DOI: 10.1002/jmri.24806] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 11/03/2014] [Indexed: 01/08/2023] Open
Abstract
BACKGROUND To implement a multidirectional motion encoding scheme for magnetic resonance elastography (MRE) of the human brain with reduced acquisition time, and investigate its performance relative to a conventional MRE scheme. METHODS The sample interval modulation (SLIM) scheme was implemented in a multishot, variable density spiral MRE sequence. The brains of seven healthy volunteers were investigated with both SLIM-MRE and conventional MRE acquisitions in a single imaging session on a clinical 3 Tesla MRI scanner with 50 Hz vibration. Following extraction of displacement fields, complex shear modulus property maps were estimated for each encoding concept. RESULTS The SLIM-MRE and conventional MRE acquisitions produced deformation fields that were nearly identical and exhibited an average correlation coefficient of 0.95 (all p < 0.05). Average properties of white matter differed between the two acquisitions by less than 5% for all volunteers, which is better than reproducibility estimates for conventional MRE alone. CONCLUSION The use of SLIM provides very similar quantitative property estimates compared with the conventional MRE encoding scheme. The SLIM acquisition is 2.5 times faster than the conventional acquisition, and may speed the adoption of MRE in clinical settings.
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Affiliation(s)
- Dieter Klatt
- The Richard and Loan Hill Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA
| | - Curtis L Johnson
- Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | - Richard L Magin
- The Richard and Loan Hill Department of Bioengineering, University of Illinois at Chicago, Chicago, Illinois, USA
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