Viscoelastic Properties of Living Human Brain by Local Frequency Estimation Applied to Distortional Wave Fields

2012 ◽  
Author(s):  
Erik H. Clayton ◽  
Guy M. Genin ◽  
Philip V. Bayly
Keyword(s):  
Viscoelastic Properties ◽  
Frequency Estimation ◽  
Equations Of Motion ◽  
Wave Fields ◽  
Shear Moduli ◽  
Lossy Medium ◽  
Displacement Wave ◽  
Magnetic Resonance Imaging Mri ◽  
Elastic Shear

The use of magnetic resonance imaging (MRI) to characterize the biomechanical material properties of tissue in vivo is an emerging application. Local frequency estimation (LFE) [1] has been used to locally extract the wavenumber κ from displacement wave fields in order to estimate the elastic shear modulus via the well-known phase velocity relation [2,3]. LFE-based inversion is attractive because it allows material parameters to be estimated without explicitly invoking the equations of motion, thus obviating the need to numerically compute the Laplacian. In this study, viscoelastic properties of brain tissue at multiple frequencies were obtained by local frequency estimation (LFE) applied to distortional wave fields. This avoids artifacts from the presence of unmodeled longitudinal waves. By use of the equation describing planar distortional wave propagation in a lossy medium, the viscoelastic shear moduli were approximated.

scholarly journals Viscoelastic properties of vimentin compared with other filamentous biopolymer networks.

1991 ◽  
Vol 113 (1) ◽  
pp. 155-160 ◽  
Author(s):  
P A Janmey ◽  
U Euteneuer ◽  
P Traub ◽  
M Schliwa
Keyword(s):  
Viscoelastic Properties ◽  
Intermediate Filament Protein ◽  
Linear Polymers ◽  
Cell Integrity ◽  
Interphase Cell ◽  
Shear Moduli ◽  
Lower Shear ◽  
Cytoplasmic Filaments ◽  
Filament Protein

The cytoplasm of vertebrate cells contains three distinct filamentous biopolymers, the microtubules, microfilaments, and intermediate filaments. The basic structural elements of these three filaments are linear polymers of the proteins tubulin, actin, and vimentin or another related intermediate filament protein, respectively. The viscoelastic properties of cytoplasmic filaments are likely to be relevant to their biologic function, because their extreme length and rodlike structure dominate the rheologic behavior of cytoplasm, and changes in their structure may cause gel-sol transitions observed when cells are activated or begin to move. This paper describes parallel measurements of the viscoelasticity of tubulin, actin, and vimentin polymers. The rheologic differences among the three types of cytoplasmic polymers suggest possible specialized roles for the different classes of filaments in vivo. Actin forms networks of highest rigidity that fluidize at high strains, consistent with a role in cell motility in which stable protrusions can deform rapidly in response to controlled filament rupture. Vimentin networks, which have not previously been studied by rheologic methods, exhibit some unusual viscoelastic properties not shared by actin or tubulin. They are less rigid (have lower shear moduli) at low strain but harden at high strains and resist breakage, suggesting they maintain cell integrity. The differences between F-actin and vimentin are optimal for the formation of a composite material with a range of properties that cannot be achieved by either polymer alone. Microtubules are unlikely to contribute significantly to interphase cell rheology alone, but may help stabilize the other networks.

scholarly journals Non-invasive diagnostics in fossils - Magnetic Resonance Imaging of pathological belemnites

2005 ◽  
Vol 2 (2) ◽  
pp. 133-140 ◽  
Author(s):  
D. Mietchen ◽  
H. Keupp ◽  
B. Manz ◽  
F. Volke
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Soft Tissue ◽  
Clinical Diagnostics ◽  
Resonance Imaging ◽  
Non Invasive ◽  
Physiological Processes ◽  
Magnetic Resonance Imaging Mri ◽  
Invasive Diagnostics

Abstract. For more than a decade, Magnetic Resonance Imaging (MRI) has been routinely employed in clinical diagnostics because it allows non-invasive studies of anatomical structures and physiological processes in vivo and to differentiate between healthy and pathological states, particularly of soft tissue. Here, we demonstrate that MRI can likewise be applied to fossilized biological samples and help in elucidating paleopathological and paleoecological questions: Five anomalous guards of Jurassic and Cretaceous belemnites are presented along with putative paleopathological diagnoses directly derived from 3D MR images with microscopic resolution. Syn vivo deformities of both the mineralized internal rostrum and the surrounding former soft tissue can be traced back in part to traumatic events of predator-prey-interactions, and partly to parasitism. Besides, evidence is presented that the frequently observed anomalous apical collar might be indicative of an inflammatory disease. These findings highlight the potential of Magnetic Resonance techniques for further paleontological applications.

scholarly journals MSCs-engineered biomimetic PMAA nanomedicines for multiple bioimaging-guided and photothermal-enhanced radiotherapy of NSCLC

2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Yipengchen Yin ◽  
Yongjing Li ◽  
Sheng Wang ◽  
Ziliang Dong ◽  
Chao Liang ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Cell Membranes ◽  
Imaging System ◽  
Fluorescence Signal ◽  
Bimodal Imaging ◽  
Red Blood Cell Membranes ◽  
Magnetic Resonance Imaging Mri ◽  
Tumor Accumulation

Abstract Background The recently developed biomimetic strategy is one of the mostly effective strategies for improving the theranostic efficacy of diverse nanomedicines, because nanoparticles coated with cell membranes can disguise as “self”, evade the surveillance of the immune system, and accumulate to the tumor sites actively. Results Herein, we utilized mesenchymal stem cell memabranes (MSCs) to coat polymethacrylic acid (PMAA) nanoparticles loaded with Fe(III) and cypate—an derivative of indocyanine green to fabricate Cyp-PMAA-Fe@MSCs, which featured high stability, desirable tumor-accumulation and intriguing photothermal conversion efficiency both in vitro and in vivo for the treatment of lung cancer. After intravenous administration of Cyp-PMAA-Fe@MSCs and Cyp-PMAA-Fe@RBCs (RBCs, red blood cell membranes) separately into tumor-bearing mice, the fluorescence signal in the MSCs group was 21% stronger than that in the RBCs group at the tumor sites in an in vivo fluorescence imaging system. Correspondingly, the T1-weighted magnetic resonance imaging (MRI) signal at the tumor site decreased 30% after intravenous injection of Cyp-PMAA-Fe@MSCs. Importantly, the constructed Cyp-PMAA-Fe@MSCs exhibited strong photothermal hyperthermia effect both in vitro and in vivo when exposed to 808 nm laser irradiation, thus it could be used for photothermal therapy. Furthermore, tumors on mice treated with phototermal therapy and radiotherapy shrank 32% more than those treated with only radiotherapy. Conclusions These results proved that Cyp-PMAA-Fe@MSCs could realize fluorescence/MRI bimodal imaging, while be used in phototermal-therapy-enhanced radiotherapy, providing desirable nanoplatforms for tumor diagnosis and precise treatment of non-small cell lung cancer.

scholarly journals Effects of Loading and Boundary Conditions on the Performance of Ultrasound Compressional Viscoelastography: A Computational Simulation Study to Guide Experimental Design

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2590
Author(s):  
Che-Yu Lin ◽  
Ke-Vin Chang
Keyword(s):  
Boundary Conditions ◽  
Simulation Study ◽  
Viscoelastic Properties ◽  
Measurement Accuracy ◽  
Computational Simulation ◽  
Vertical Direction ◽  
Fixation Method ◽  
Element Analysis ◽  
Sample Container

Most biomaterials and tissues are viscoelastic; thus, evaluating viscoelastic properties is important for numerous biomedical applications. Compressional viscoelastography is an ultrasound imaging technique used for measuring the viscoelastic properties of biomaterials and tissues. It analyzes the creep behavior of a material under an external mechanical compression. The aim of this study is to use finite element analysis to investigate how loading conditions (the distribution of the applied compressional pressure on the surface of the sample) and boundary conditions (the fixation method used to stabilize the sample) can affect the measurement accuracy of compressional viscoelastography. The results show that loading and boundary conditions in computational simulations of compressional viscoelastography can severely affect the measurement accuracy of the viscoelastic properties of materials. The measurement can only be accurate if the compressional pressure is exerted on the entire top surface of the sample, as well as if the bottom of the sample is fixed only along the vertical direction. These findings imply that, in an experimental validation study, the phantom design should take into account that the surface area of the pressure plate must be equal to or larger than that of the top surface of the sample, and the sample should be placed directly on the testing platform without any fixation (such as a sample container). The findings indicate that when applying compressional viscoelastography to real tissues in vivo, consideration should be given to the representative loading and boundary conditions. The findings of the present simulation study will provide a reference for experimental phantom designs regarding loading and boundary conditions, as well as guidance towards validating the experimental results of compressional viscoelastography.

scholarly journals Perspectives on the Role of Magnetic Resonance Imaging (MRI) for Noninvasive Evaluation of Diabetic Kidney Disease

2021 ◽  
Vol 10 (11) ◽  
pp. 2461
Author(s):  
José María Mora-Gutiérrez ◽  
María A. Fernández-Seara ◽  
Rebeca Echeverria-Chasco ◽  
Nuria Garcia-Fernandez
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Kidney Disease ◽  
Diabetic Kidney Disease ◽  
Imaging Biomarkers ◽  
Major Advance ◽  
Resonance Imaging ◽  
Diabetic Kidney ◽  
Magnetic Resonance Imaging Mri

Renal magnetic resonance imaging (MRI) techniques are currently in vogue, as they provide in vivo information on renal volume, function, metabolism, perfusion, oxygenation, and microstructural alterations, without the need for exogenous contrast media. New imaging biomarkers can be identified using these tools, which represent a major advance in the understanding and study of the different pathologies affecting the kidney. Diabetic kidney disease (DKD) is one of the most important diseases worldwide due to its high prevalence and impact on public health. However, its multifactorial etiology poses a challenge for both basic and clinical research. Therefore, the use of novel renal MRI techniques is an attractive step forward in the comprehension of DKD, both in its pathogenesis and in its detection and surveillance in the clinical practice. This review article outlines the most promising MRI techniques in the study of DKD, with the purpose of stimulating their clinical translation as possible tools for the diagnosis, follow-up, and monitoring of the clinical impacts of new DKD treatments.

scholarly journals Meyer’s Loop Anatomy Demonstrated Using Diffusion Tensor MR Imaging and Fiber Tractography at 3T

2014 ◽  
Vol 60 (5) ◽  
pp. 215-222 ◽  
Author(s):  
Cristina Goga ◽  
Zeynep Firat ◽  
Klara Brinzaniuc ◽  
Is Florian
Keyword(s):  
Diffusion Tensor Imaging ◽  
Diffusion Tensor ◽  
Region Of Interest ◽  
Fiber Tractography ◽  
Brain Images ◽  
3 Dimensional ◽  
Software Release ◽  
Magnetic Resonance Imaging Mri ◽  
Meyer’S Loop

Abstract Objective: The ultimate anatomy of the Meyer’s loop continues to elude us. Diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT) may be able to demonstrate, in vivo, the anatomy of the complex network of white matter fibers surrounding the Meyer’s loop and the optic radiations. This study aims at exploring the anatomy of the Meyer’s loop by using DTI and fiber tractography. Methods: Ten healthy subjects underwent magnetic resonance imaging (MRI) with DTI at 3 T. Using a region-of-interest (ROI) based diffusion tensor imaging and fiber tracking software (Release 2.6, Achieva, Philips), sequential ROI were placed to reconstruct visual fibers and neighboring projection fibers involved in the formation of Meyer’s loop. The 3-dimensional (3D) reconstructed fibers were visualized by superimposition on 3-planar MRI brain images to enhance their precise anatomical localization and relationship with other anatomical structures. Results: Several projection fiber including the optic radiation, occipitopontine/parietopontine fibers and posterior thalamic peduncle participated in the formation of Meyer’s loop. Two patterns of angulation of the Meyer’s loop were found. Conclusions: DTI with DTT provides a complimentary, in vivo, method to study the details of the anatomy of the Meyer’s loop.

scholarly journals Cervical cord myelin abnormality is associated with clinical disability in multiple sclerosis

2021 ◽  
pp. 135245852110017
Author(s):  
Lisa Eunyoung Lee ◽  
Irene M Vavasour ◽  
Adam Dvorak ◽  
Hanwen Liu ◽  
Shawna Abel ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Progressive Multiple Sclerosis ◽  
Dorsal Column ◽  
Cervical Cord ◽  
In Vivo Measurement ◽  
Subclinical Disease ◽  
Healthy Control ◽  
Magnetic Resonance Imaging Mri ◽  
Relapsing Remitting Multiple Sclerosis

Background: Myelin water imaging (MWI) was recently optimized to provide quantitative in vivo measurement of spinal cord myelin, which is critically involved in multiple sclerosis (MS) disability. Objective: To assess cervical cord myelin measurements in relapsing-remitting multiple sclerosis (RRMS) and progressive multiple sclerosis (ProgMS) participants and evaluate the correlation between myelin measures and clinical disability. Methods: We used MWI data from 35 RRMS, 30 ProgMS, and 28 healthy control (HC) participants collected at cord level C2/C3 on a 3 T magnetic resonance imaging (MRI) scanner. Myelin heterogeneity index (MHI), a measurement of myelin variability, was calculated for whole cervical cord, global white matter, dorsal column, lateral and ventral funiculi. Correlations were assessed between MHI and Expanded Disability Status Scale (EDSS), 9-Hole Peg Test (9HPT), timed 25-foot walk, and disease duration. Results: In various regions of the cervical cord, ProgMS MHI was higher compared to HC (between 9.5% and 31%, p ⩽ 0.04) and RRMS (between 13% and 26%, p ⩽ 0.02), and ProgMS MHI was associated with EDSS ( r = 0.42–0.52) and 9HPT ( r = 0.45–0.52). Conclusion: Myelin abnormalities within clinically eloquent areas are related to clinical disability. MWI metrics have a potential role for monitoring subclinical disease progression and adjudicating treatment efficacy for new therapies targeting ProgMS.

scholarly journals Immunocompatibility of a new dual modality contrast agent based on radiolabeled iron-oxide nanoparticles

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Maria-Argyro Karageorgou ◽  
Dimosthenis Stamopoulos
Keyword(s):  
Complete Blood Count ◽  
Morphological Characteristics ◽  
Mononuclear Phagocyte ◽  
Dual Modality ◽  
Immunodeficient Mice ◽  
Force Microscopy ◽  
Magnetic Resonance Imaging Mri ◽  
Diagnostic Applications

AbstractRadiolabeled magnetic nanoparticles are promising candidates as dual-modality-contrast-agents (DMCA) for diagnostic applications. The immunocompatibility of a new DMCA is a prerequisite for subsequent in vivo applications. Here, a new DMCA, namely Fe3O4 nanoparticles radiolabeled with 68Ga, is subjected to immunocompatibility tests both in vitro and in vivo. The in vitro immunocompatibility of the DMCA relied on incubation with donated human WBCs and PLTs (five healthy individuals). Optical microscopy (OM) and atomic force microscopy (AFM) were employed for the investigation of the morphological characteristics of WBCs and PLTs. A standard hematology analyzer (HA) provided information on complete blood count. The in vivo immunocompatibility of the DMCA was assessed through its biodistribution among the basic organs of the mononuclear phagocyte system in normal and immunodeficient mice (nine in each group). In addition, Magnetic Resonance Imaging (MRI) data were acquired in normal mice (three). The combined OM, AFM and HA in vitro data showed that although the DMCA promoted noticeable activation of WBCs and PLTs, neither degradation nor clustering were observed. The in vivo data showed no difference of the DMCA biodistribution between the normal and immunodeficient mice, while the MRI data prove the efficacy of the particular DMCA when compared to the non-radiolabeled, parent CA. The combined in vitro and in vivo data prove that the particular DMCA is a promising candidate for future in vivo applications.

scholarly journals The Inferior Colliculus in Alcoholism and Beyond

2020 ◽  
Vol 14 ◽  
Author(s):  
Tanuja Bordia ◽  
Natalie M. Zahr
Keyword(s):  
Inferior Colliculus ◽  
Ethanol Exposure ◽  
Ethanol Withdrawal ◽  
Hypoxic Injury ◽  
Auditory Gating ◽  
Korsakoff Syndrome ◽  
Altered Metabolism ◽  
Magnetic Resonance Imaging Mri ◽  
Inferior Colliculi

Post-mortem neuropathological and in vivo neuroimaging methods have demonstrated the vulnerability of the inferior colliculus to the sequelae of thiamine deficiency as occurs in Wernicke-Korsakoff Syndrome (WKS). A rich literature in animal models ranging from mice to monkeys—including our neuroimaging studies in rats—has shown involvement of the inferior colliculi in the neural response to thiamine depletion, frequently accomplished with pyrithiamine, an inhibitor of thiamine metabolism. In uncomplicated alcoholism (i.e., absent diagnosable neurological concomitants), the literature citing involvement of the inferior colliculus is scarce, has nearly all been accomplished in preclinical models, and is predominately discussed in the context of ethanol withdrawal. Our recent work using novel, voxel-based analysis of structural Magnetic Resonance Imaging (MRI) has demonstrated significant, persistent shrinkage of the inferior colliculus using acute and chronic ethanol exposure paradigms in two strains of rats. We speculate that these consistent findings should be considered from the perspective of the inferior colliculi having a relatively high CNS metabolic rate. As such, they are especially vulnerable to hypoxic injury and may be provide a common anatomical link among a variety of disparate insults. An argument will be made that the inferior colliculi have functions, possibly related to auditory gating, necessary for awareness of the external environment. Multimodal imaging including diffusion methods to provide more accurate in vivo visualization and quantification of the inferior colliculi may clarify the roles of brain stem nuclei such as the inferior colliculi in alcoholism and other neuropathologies marked by altered metabolism.

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