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By Allen Yang
About this collection
Selection of citations from the paper "3D rotational shear wave elasticity imaging (3D-RSWEI) in anisotropic lattice phantoms" by Shruthi Srinivasan, et al.
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3D rotational shear wave elasticity imaging (3D-RSWEI) in anisotropic lattice phantoms - ScienceDirect
This study presents the characterization of 3D-printed anisotropic hydrogel lattice phantoms using 3D rotational shear wave elasticity imaging (3D-RSWEI). The phantoms were originally developed for magnetic resonance elastography (MRE) applications. Shear wave speeds were measured in two lattice structures submerged in water and embedded in isotropic poly-vinyl alcohol (PVA) of different stiffnesses. The results show anisotropic shear wave propagation in the lattices, with faster wave speeds parallel to the scaling direction. Embedding the lattices in PVA reduced shear wave speeds and anisotropy compared to measurements in water. The study demonstrates the feasibility of using 3D-RSWEI to characterize novel anisotropic tissue-mimicking phantoms.
Key Takeaways
- 3D-RSWEI can effectively characterize anisotropic mechanical properties of 3D-printed hydrogel lattice phantoms.
- Embedding lattices in PVA reduces shear wave speeds and anisotropy compared to water-submerged measurements.
- The study highlights the potential of 3D-RSWEI for calibrating and validating elastography techniques in anisotropic tissues.
3D Printing of Heterogeneous Ultrasound Phantoms
Researchers developed a projection-based stereolithography (pSLA) technique to fabricate customizable ultrasound phantoms with complex geometries and heterogeneous properties. The method allows for voxel-specific control over ultrasound backscatter and stiffness, enabling the creation of phantoms that mimic native tissue properties. The phantoms were fabricated using poly(ethylene glycol) diacrylate (PEGDA) hydrogels and demonstrated stable ultrasound properties over six weeks. The technique enables the creation of complex channel networks and anisotropic elasticity phantoms, making it suitable for various ultrasound imaging applications, including elasticity imaging and Doppler imaging.
Key Takeaways
- The pSLA technique enables fabrication of complex ultrasound phantoms with customizable backscatter and elasticity values.
- The phantoms demonstrated stable ultrasound properties over six weeks, with minimal changes in backscatter signal and contrast-to-noise ratio.
- The technique allows for creation of complex channel networks and anisotropic elasticity phantoms, making it suitable for various ultrasound imaging applications.
- The use of PEGDA hydrogels and silica particles enables the creation of phantoms with tissue-mimicking properties.
- The method has potential applications in developing and validating novel ultrasound imaging techniques, such as super-resolution imaging and acoustic angiography.
Speed of sound in muscle for use in sonomicrometry - ScienceDirect
The speed of sound in muscle tissue is crucial for accurate distance measurements using sonomicrometry. Studies have shown that the speed of sound in both cardiac and skeletal muscle can be approximated by multiplying the speed of sound in pure water at the measurement temperature by 1.045. The speed of sound in pure water varies with temperature, and a simplified equation is presented for the temperature range 0-50 °C. The effects of temperature, contractile state, and muscle composition on the speed of sound in muscle are discussed. The difference in speed between longitudinal and transverse directions is small (<0.8%) and can often be ignored. Investigators should be aware of the much greater speed of sound in tendons and potential variations with loading.
Key Takeaways
- The speed of sound in muscle can be approximated by multiplying the speed of sound in pure water by 1.045.
- Temperature significantly affects the speed of sound in muscle and should be considered in sonomicrometry measurements.
- The difference in speed between longitudinal and transverse directions in muscle is typically small and can be ignored in most cases.
- Muscle composition has a minimal effect on the speed of sound, but the presence of tendons can significantly affect measurements.
Anisotropic composite material phantom to improve skeletal muscle characterization using magnetic resonance elastography - ScienceDirect
Researchers developed a novel 3D-printed composite phantom for Magnetic Resonance Elastography (MRE) experiments to improve skeletal muscle characterization. The phantom exhibits anisotropic heterogeneous viscoelastic properties comparable to skeletal muscle tissue. MRE experiments and finite element simulations demonstrated the phantom's degree of anisotropy is similar to literature values for muscle tissue. The study aimed to create a tissue-mimicking phantom with uniform controllable anisotropic properties to aid in developing and evaluating MRE inversion algorithms for anisotropic tissues. The phantom was made of 15% w/v crosslinked gelatin solution for fibers and 5% w/v gelatin solution for the matrix. The displacement maps from MRE experiments and simulations showed elliptical wavefronts elongated in the plane with higher shear modulus. This phantom design could help optimize MRE protocols for estimating mechanical properties in anisotropic tissues like skeletal muscle.
Key Takeaways
- The novel composite phantom mimics skeletal muscle's anisotropic viscoelastic properties, enabling more accurate MRE characterization.
- MRE experiments and finite element simulations validated the phantom's anisotropic behavior, showing comparable degree of anisotropy to muscle tissue.
- This phantom can aid in developing and evaluating MRE inversion algorithms for anisotropic tissues, potentially improving diagnosis and monitoring of neuromuscular disorders.
- The study highlights the importance of accounting for heterogeneity and anisotropy in MRE measurements of skeletal muscle tissue.
- The phantom's design and materials provide a useful tool for optimizing MRE protocols for anisotropic tissue characterization.
Viscoelastic and Anisotropic Mechanical Properties of in vivo Muscle Tissue Assessed by Supersonic Shear Imaging - ScienceDirect
The biomechanical properties of skeletal muscle are complex and difficult to assess due to its anisotropic, viscoelastic, and dynamic nature. This study uses supersonic shear imaging, a noninvasive ultrasound-based technique, to characterize the mechanical properties of the brachialis muscle in vivo. The technique combines an ultra-fast ultrasonic system with the remote generation of transient mechanical forces into tissue via the radiation force of focused ultrasonic beams. Local tissue velocity maps are obtained using a conventional speckle tracking technique, providing a full movie of shear wave propagation through the entire muscle. Shear wave group velocities are estimated using a time-of-flight algorithm, allowing for the assessment of anisotropic properties by tilting the probe head with respect to the main muscular fibers direction. The dispersion of shear waves is studied for different configurations, and shear modulus and shear viscosity are quantitatively assessed assuming the viscoelastic Voigt's model. The study provides a complete set of quantitative and in vivo parameters describing the muscle's mechanical properties as a function of active voluntary contraction and passive extension of healthy volunteers.
Key Takeaways
- The study demonstrates the use of supersonic shear imaging to assess the viscoelastic and anisotropic mechanical properties of in vivo muscle tissue.
- The technique provides a complete set of quantitative parameters describing muscle mechanical properties, including shear modulus, shear viscosity, and anisotropy.
- The results show that the mechanical properties of muscle tissue vary with contraction level, anisotropy, and passive extension, highlighting the complexity of muscle biomechanics.
Measurements of mechanical anisotropy in brain tissue and implications for transversely isotropic material models of white matter - ScienceDirect
White matter in the brain exhibits mechanical anisotropy in tension and shear due to its structurally anisotropic composition of aligned axonal fibers. Experimental measurements using shear and asymmetric indentation tests show differences in both tensile and shear moduli, indicating that hyperelastic models of white matter should include both *I* 4 and *I* 5 pseudo-invariants to capture this anisotropy. The study tested samples of white and gray matter from lamb brains, finding white matter to be anisotropic in both shear and indentation, while gray matter appeared isotropic. Results highlight the importance of including both fiber stretch and fiber-matrix interactions in material models of white matter. The findings have implications for predicting brain tissue deformation and injury in traumatic brain injuries.
Key Takeaways
- Hyperelastic models of white matter should include both *I* 4 and *I* 5 pseudo-invariants to capture mechanical anisotropy.
- White matter exhibits anisotropy in both tension and shear, while gray matter appears isotropic.
- Experimental measurements using combined shear and indentation tests can estimate parameters of transversely isotropic material models.
- The study's findings have implications for predicting brain tissue deformation and injury in traumatic brain injuries.
- The results guide the selection and parameterization of more general hyperelastic models of white matter.
Cardiac mechanostructure: Using mechanics and anisotropy as inspiration for developing epicardial therapies in treating myocardial infarction - ScienceDirect
The mechanical environment and anisotropic structure of the heart modulate cardiac function. During myocardial infarction (MI) and subsequent healing, this landscape changes significantly. Epicardial restraint devices have emerged as a new class of cardiac therapies to enhance MI treatment and limit its progression to heart failure (HF). This review focuses on the mechanical and structural properties of the healthy and infarcted myocardium, discussing epicardial therapies inspired by the mechanics and anisotropy of the heart. Both passive devices featuring biomaterials and active devices with robotic and cellular components are explored as potential therapies. The review provides a detailed analysis of the engineering techniques used to fabricate these therapies and their impact on cardiac function.
Key Takeaways
- Understanding cardiac mechanostructure is crucial for developing effective epicardial therapies for MI.
- Epicardial restraint devices can reduce ventricular wall tension and improve cardiac function post-MI.
- Both passive and active epicardial therapies show promise in treating MI and preventing HF.
- The mechanical properties of biomaterials used in epicardial therapies must be carefully considered to avoid inhibiting cardiac function.
- Active epicardial therapies, including robotic and cellular components, offer new avenues for treating large infarcts and restoring cardiac function.
Ultrasound shear wave velocity in skeletal muscle: A reproducibility study - ScienceDirect
Shear wave imaging (SWI) is an elastography technique that measures shear elastic modulus via the velocity of a local shear wave. The study assessed the reliability and reproducibility of shear wave velocities (SWV) measurements in normal skeletal muscles. Measurements were performed on 16 volunteers by two radiologists on medial gastrocnemius and tibialis anterior muscles. Each muscle was evaluated in 5 different sites with three measurements for each site in transverse and longitudinal planes. Reliability of SWV measurements was excellent in the longitudinal plane and fair to good in the transverse plane. Inter/intra-operator reproducibility per site was fair to good in the longitudinal plane and poor to fair in the transverse plane. For global values of the whole muscle, ICC showed good agreement in the longitudinal plane and fair agreement in the transverse plane.
Key Takeaways
- SWI measurements are reliable when performed in rigorous conditions
- Longitudinal plane shows better reproducibility than transverse plane
- Reproducibility varies between different muscle sites and operators
- Global muscle SWV values show good intra-operator reproducibility in longitudinal plane
- Precision errors need to be considered when interpreting SWV measurements
Identification of the testing parameters in high frequency dynamic shear measurement on agarose gels - ScienceDirect
Dynamic mechanical analysis (DMA) on agarose gels is used to validate magnetic resonance elastography (MRE) measurements and understand biological responses to dynamic loadings. The study investigates parameters affecting DMA shear modulus measurements, including sample thickness, shear strain, testing frequency, and compressive clamping strain. Results show that sample thickness must be sufficiently small (1 mm) to prevent erroneous fluctuations in measured modulus. Appropriate levels of shear strain (⩽0.5%) and compressive clamping strain (5-10%) are necessary to overcome slippage without causing boundary stress non-uniformity or micro-cracks. The shear modulus of agarose gel decreases at shear strains above 1% due to irreversible effects like slippage or micro-cracking. Compressive clamping strain is required to maintain equilibrium, with 5-10% being a feasible range. The study's findings are critical for designing dynamic shear measurements on gels for biomedical investigations.
Key Takeaways
- Sample thickness should be minimized (1 mm) for reliable DMA measurements
- Shear strain should be limited to ⩽0.5% to prevent modulus decrease
- Compressive clamping strain between 5-10% is recommended to prevent slippage
- Testing frequency affects measured shear modulus, with fluctuations above 40 Hz
- Findings are applicable to biological soft tissues and tissue-mimicking gels
Analysis of multiple shear wave modes in a nonlinear soft solid: Experiments and finite element simulations with a tilted acoustic radiation force - ScienceDirect
This study demonstrates the feasibility of exciting and detecting multiple shear wave modes in a nonlinear soft solid using acoustic radiation force-based shear wave elastography (SWE). Experiments and finite element simulations were performed on a uniaxially stretched phantom, showing the propagation of two shear wave modes (SH and SV) when the acoustic radiation force was tilted with respect to the material's symmetry axis. The results demonstrate the potential of analyzing multiple shear wave modes to refine material characterization and improve disease diagnosis.
Key Takeaways
- Analyzing multiple shear wave modes can provide more information about tissue material properties.
- Tilting the acoustic radiation force axis enables the excitation and detection of both SH and SV wave modes.
- The study demonstrates the feasibility of using SWE to characterize nonlinear soft solids.
Strength improvement in injection-molded jute-fiber-reinforced polylactide green-composites - ScienceDirect
The mechanical properties of jute-fiber-reinforced polylactic acid (PLA) green-composites were investigated. A long fiber pellet was developed to obtain a high aspect ratio of residual fiber after injection molding. Comparative studies were carried out using shorter fiber pellets compounded by different screw configurations in a twin-screw extruder. The composites made of short fiber pellet exhibited optimal mechanical performance due to efficient load transfer from matrix to fiber and improved interfacial strength. Compounding with a twin-screw extruder decreased the overall aspect ratio of residual fibers but significantly facilitated fiber dispersion and decohesion of jute bundles to elementary fibers. The findings provide insight into critical parameters for developing high-performing jute/PLA composites.
Key Takeaways
- Suppression of PLA hydrolysis is crucial for improving mechanical properties
- Short fiber pellets showed better mechanical performance than long fiber pellets
- High compounding intensity improves fiber dispersion and interfacial strength
- Twin-screw extruder facilitates decohesion of jute bundles to elementary fibers
- Improved fiber dispersion leads to efficient load transfer and enhanced mechanical properties
Analysis of multiple shear wave modes in a nonlinear soft solid: Experiments and finite element simulations with a tilted acoustic radiation force - ScienceDirect
Tissue nonlinearity is conventionally measured in shear wave elastography by studying wave speed changes caused by tissue deformation, known as the acoustoelastic effect. This work demonstrates proof of concept using experiments and finite element simulations in a uniaxially stretched phantom by tilting the acoustic radiation force excitation axis. Using this setup, two propagating shear wave modes were visualized across the stretch direction for stretches larger than 140%. Complementary simulations were performed using material parameters determined from mechanical testing, enabling conversion of observed shear wave behavior into a representative constitutive law for the phantom material, i.e., the Isihara model. Shear wave elastography measurements were performed for various uniaxial stretch levels and acoustic radiation force tilt angles. The study demonstrates the potential of measuring shear wave propagation in combination with shear wave modeling in complex materials as a non-invasive alternative for mechanical testing.
Key Takeaways
- Tilting the acoustic radiation force excitation axis enables visualization of multiple shear wave modes in nonlinear soft solids.
- The Isihara material model accurately represents the shear wave behavior observed in experiments.
- Analysis of multiple shear wave modes provides additional information about material parameters and internal stress state.
- The study demonstrates the potential of shear wave elastography for advanced material characterization.
- The combination of experiments and finite element simulations is a promising approach for non-invasive mechanical material characterization.