An In-Vivo Measurement and Analysis of Viscoelastic Properties of the Spinal Cord of Cats

1988 ◽  
Vol 110 (2) ◽  
pp. 115-122 ◽  
Author(s):  
Guan-Liang Chang ◽  
Tin-Kan Hung ◽  
William W. Feng
Keyword(s):  
Spinal Cord ◽  
Stress Relaxation ◽  
Viscoelastic Properties ◽  
Nonlinear Characteristics ◽  
In Vivo Measurement ◽  
Recovery Curves ◽  
Measurement And Analysis ◽  
Linear Viscoelastic ◽  
Prolonged Stress

An in-vivo experimental technique was employed to determine the linear and nonlinear characteristics of viscoelastic properties of the spinal cord of anesthetized cats. The stress relaxation and recovery curves were reproducible in a group of cat experiments. The data of linear viscoelastic properties were used to develop a power law model with Boltzmann’s convolution integral. The model was capable of predicting a prolonged stress relaxation and recovery curve. For larger deformation, the results were quantified using a nonlinear analysis of viscoelastic response of the spinal cord under the uniaxial experiment.

In vivo measurement and analysis of bone strain

1979 ◽  
Vol 12 (8) ◽  
pp. 631
Author(s):  
D.J. Smith ◽  
D.R. Carter ◽  
D.M. Spengler ◽  
V.H. Frankel
Keyword(s):  
Bone Strain ◽  
In Vivo Measurement ◽  
Measurement And Analysis

An In Vivo Method for Measuring Turbulence in Mechanical Prosthesis Leakage Jets

2004 ◽  
Vol 126 (1) ◽  
pp. 26-35 ◽  
Author(s):  
Brandon R. Travis ◽  
Thomas D. Christensen ◽  
Morten Smerup ◽  
Morten S. Olsen ◽  
J. Michael Hasenkam ◽  
...  
Keyword(s):  
Mechanical Heart Valve ◽  
Maximum Velocity ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Mechanical Prosthesis ◽  
Analytical Technique ◽  
In Vivo Measurement ◽  
Measurement And Analysis

This work introduces a method for the in vivo measurement and analysis of turbulence within the leakage of a mechanical heart valve. Several analysis techniques were applied to ultrasound measurements acquired within the atrium of a pig, and error associated with these techniques was analyzed. The technique chosen applies cyclic averaging to mean and maximum velocity measurements within small, normalized phase windows to calculate Reynolds normal stresses in the direction of the ultrasound beam. Maximum shear stresses are estimated from these normal stresses using an analytical technique. The stresses observed were smaller than those reported from previous in vitro simulations.

In Vivo Measurement of Cervical Spinal Cord Deformation During Traumatic Spinal Cord Injury in a Rodent Model

2015 ◽  
Vol 44 (4) ◽  
pp. 1285-1298 ◽  
Author(s):  
Tim Bhatnagar ◽  
Jie Liu ◽  
Andrew Yung ◽  
Peter A. Cripton ◽  
Piotr Kozlowski ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Cervical Spinal Cord ◽  
Rodent Model ◽  
Traumatic Spinal Cord Injury ◽  
In Vivo Measurement ◽  
Cord Injury

Different Passive Viscoelastic Properties Between the Left and Right Ventricles in Healthy Adult Ovine

2021 ◽  
Author(s):  
Wenqiang Liu ◽  
Michael Nguyen-Truong ◽  
Matt Ahern ◽  
Kevin Labus ◽  
Christian Puttlitz ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Properties ◽  
Healthy Adult ◽  
Ex Vivo ◽  
Longitudinal Direction ◽  
Mechanical Tests ◽  
Mortality And Morbidity ◽  
Linear Viscoelastic ◽  
Left And Right ◽  
Relaxation Curves

Abstract Ventricle dysfunction is the most common cause of heart failure, which leads to high mortality and morbidity. The mechanical behavior of the ventricle is critical to its physiological function. It is known that the ventricle is anisotropic and viscoelastic. However, the understanding of ventricular viscoelasticity is much less than that of its elasticity. Moreover, the left and right ventricles (LV&RV) are different in embryologic origin, anatomy, and function, but whether they distinguish in viscoelastic properties is unclear. We hypothesized that passive viscoelasticity is different between healthy LVs and RVs. Ex vivo cyclic biaxial tensile mechanical tests (1, 0.1, 0.01Hz) and stress relaxation (strain of 3, 6, 9, 12 15%) were performed for ventricles from healthy adult sheep. Outflow track direction was defined as the longitudinal direction. Hysteresis stress-strain loops and stress relaxation curves were obtained to quantify the viscoelastic properties. We found that the RV had more pronounced frequency-dependent viscoelastic changes than the LV. Under the physiological frequency (1Hz), the LV was more anisotropic in the elasticity and stiffer than the RV in both directions, whereas the RV was more anisotropic in the viscosity and more viscous than the LV in the longitudinal direction. The LV was quasi-linear viscoelastic in the longitudinal but not circumferential direction, and the RV was non-linear viscoelastic in both directions. This study is the first to investigate passive viscoelastic differences in healthy LVs and RVs, and the findings will deepen the understanding of biomechanical mechanisms of ventricular function.

scholarly journals Comparative analysis of indentation and magnetic resonance elastography for measuring viscoelastic properties

2021 ◽  
Author(s):  
Yu Chen ◽  
Suhao Qiu ◽  
Zhao He ◽  
Fuhua Yan ◽  
Ruokun Li ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Viscoelastic Properties ◽  
Soft Tissues ◽  
Biological Tissues ◽  
Magnetic Resonance Elastography ◽  
Small Samples ◽  
Model Parameters ◽  
In Vivo Measurement ◽  
Pathological Behavior

Abstract Measurement the viscoelastic properties is important for studying the developmental and pathological behavior of soft biological tissues. Magnetic resonance elastography (MRE) is a non-invasive method for in vivo measurement of tissue viscoelasticity. As a flexible method capable of testing small samples, indentation has been widely used for characterizing soft tissues. Using 2nd-order Prony series and dimensional analysis, we analyzed and compared the model parameters estimated from both indentation and MRE. Conversions of the model parameters estimated from the two methods were established. We found that the indention test is better at capturing the dynamic response of tissues at a frequency less than 10 Hz, while MRE is better for describing the frequency responses at a relatively higher range. The results provided helpful information for testing soft tissues using indentation and MRE. The models analyzed are also helpful for quantifying the frequency response of viscoelastic tissues. Graphic Abstract

scholarly journals Architecture and Composition Dictate Viscoelastic Properties of Organ-Derived Extracellular Matrix Hydrogels

Polymers ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 3113
Author(s):  
Francisco Drusso Martinez-Garcia ◽  
Roderick Harold Jan de Hilster ◽  
Prashant Kumar Sharma ◽  
Theo Borghuis ◽  
Machteld Nelly Hylkema ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Stress Relaxation ◽  
Left Ventricle ◽  
Viscoelastic Properties ◽  
Maxwell Model ◽  
Architectural Support ◽  
Dependent Part ◽  
Physical Features ◽  
Cardiac Left Ventricle

The proteins and polysaccharides of the extracellular matrix (ECM) provide architectural support as well as biochemical and biophysical instruction to cells. Decellularized, ECM hydrogels replicate in vivo functions. The ECM’s elasticity and water retention renders it viscoelastic. In this study, we compared the viscoelastic properties of ECM hydrogels derived from the skin, lung and (cardiac) left ventricle and mathematically modelled these data with a generalized Maxwell model. ECM hydrogels from the skin, lung and cardiac left ventricle (LV) were subjected to a stress relaxation test under uniaxial low-load compression at a 20%/s strain rate and the viscoelasticity determined. Stress relaxation data were modelled according to Maxwell. Physical data were compared with protein and sulfated GAGs composition and ultrastructure SEM. We show that the skin-ECM relaxed faster and had a lower elastic modulus than the lung-ECM and the LV-ECM. The skin-ECM had two Maxwell elements, the lung-ECM and the LV-ECM had three. The skin-ECM had a higher number of sulfated GAGs, and a highly porous surface, while both the LV-ECM and the lung-ECM had homogenous surfaces with localized porous regions. Our results show that the elasticity of ECM hydrogels, but also their viscoelastic relaxation and gelling behavior, was organ dependent. Part of these physical features correlated with their biochemical composition and ultrastructure.

An Experimental and Analytical Evaluation of the Nonlinear Viscoelastic Properties of the Healing Medial Collateral Ligament in a Goat Model

2003 ◽  
Author(s):  
S. D. Abramowitch ◽  
T. D. Clineff ◽  
R. E. Debski ◽  
S. L.-Y. Woo
Keyword(s):  
Stress Relaxation ◽  
Medial Collateral Ligament ◽  
Viscoelastic Properties ◽  
Soft Tissues ◽  
Viscoelastic Behavior ◽  
Collateral Ligament ◽  
Relaxation Experiment ◽  
Nonlinear Viscoelastic ◽  
Linear Viscoelastic Behavior ◽  
Linear Viscoelastic

The medial collateral ligament (MCL) is one of the most frequently injured ligaments in the knee. Although it can heal spontaneously after rupture, laboratory studies have shown that the mechanical properties of the healing MCL remain inferior to normal for up to two years after injury (1). Additionally, the healing MCL has been shown to display increased amounts of stress relaxation and creep (2). In order to more completely describe the viscoelastic properties of healing ligaments, we propose to use the Quasi-Linear Viscoelastic (QLV) theory formulated by Fung (1972). This theory has been used to successfully describe the viscoelastic properties of many soft-tissues (3). Recently, our research center has developed an improved approach to determine the constants describing the QLV theory based on data collected from a stress relaxation experiment that utilizes a slow strain rate during loading. This approach allows for experimental errors that commonly result from fast strain rates to be avoided (ex. overshoot) (4). Therefore, the objective of this study were to use this new approach to determine the constants describing the quasi-linear viscoelastic behavior of the healing goat MCL at 12 weeks after injury.

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