How to find the attenuation of the transverse shear wave in ultrasonics?5 answersTo find the attenuation of the transverse shear wave in ultrasonics, a revisited frequency shift (R-FS) method has been proposed, which improves the robustness of shear wave attenuation imaging. This method involves assuming the shape parameter of the gamma distribution fitting shear wave spectra varies with distance and utilizing an adaptive random sample consensus (A-RANSAC) line fitting method to prevent outlier attenuation values in the presence of noise. The R-FS method has shown significant improvements in reducing coefficients of variation and normalized root-mean-square errors compared to other methods like the FS method, two-point frequency shift (2P-FS), and attenuation measuring US shear wave elastography (AMUSE). This approach has been validated on simulated phantoms, experimental gel phantoms, and in vivo liver acquisitions, demonstrating its effectiveness in accurately assessing shear wave attenuation in different settings.
What is sound wave?5 answersA sound wave is a mechanical disturbance that travels through a medium, such as air, water, or solids, as a longitudinal wave, where particles oscillate in the same direction as the wave's propagation. These pressure oscillations are caused by vibrating sources like guitar strings, vocal cords, tuning forks, or loudspeaker diaphragms. Sound waves have frequencies ranging from one to tens of thousands of Hertz, with the maximum human hearing ability at 20 kHz. The characteristics of a sound wave include velocity, frequency, and wavelength, which are determined by the source of the vibration and the medium through which the wave propagates. Acoustic waves can be created and detected using piezoelectric materials, revolutionizing acoustic wave sensors and devices.
What is a sound wave ?4 answersA sound wave is a disturbance that travels through a medium, such as air, water, or solids, as a series of compressions and rarefactions of pressure. It is a mechanical wave that requires a medium with properties of inertia and elasticity for its propagation. Sound waves can be created by vibrating sources, such as guitar strings, vocal cords, tuning forks, or speaker diaphragms. The particles of the medium oscillate back and forth in the same direction as the wave propagates, resulting in longitudinal waves. Sound waves have specific characteristics, including velocity, frequency, and wavelength, which determine their shape and pitch. They can be detected and measured using sound sensors or transducers that convert mechanical vibrations into electrical signals. Overall, sound waves are disturbances in an elastic medium that propagate through compressions and rarefactions of pressure, creating audible or inaudible vibrations.
What are the limitations of the conventional shear wave time-of-flight measurement?3 answersThe limitations of conventional shear wave time-of-flight measurement include uncertainties and biases arising from system dependent parameters. These errors can lead to inaccuracies in shear wave speed (SWS) measurements. Sources of uncertainty include arrival time estimation noise, speckle bias, master clock jitter, and phase aberration. On the other hand, biases in SWS measurements can be caused by pulse repetition frequency and beamforming errors, as well as coupling medium sound speed mismatch. Additionally, the measurement of shear wave speed can be transducer, depth, and lateral tracking range dependent, leading to measurement bias. These limitations must be taken into account to ensure accurate and precise SWS measurements for clinical use.
How do you characterize skywave plan wave and surface wave into transverse wave and longitudinal wave?5 answersSkywave propagation and surface wave propagation are two principal modes of radiowave propagation at frequencies below 2 MHz. Skywave propagation refers to the reflection of radio waves off the ionosphere, allowing them to travel long distances. Surface wave propagation, on the other hand, occurs when radio waves travel along the surface of the Earth. These modes are introduced and described in the papers by John Milsomand Lai Zhenxiong. While the papers do not specifically characterize these modes as transverse or longitudinal waves, they provide information on their application and prediction methods. The papers focus on the planning engineer's use of these modes and provide relevant data sources, prediction procedures, and computer programs for their application.
How can reverberant shear wave elasto be used to study the mechanical properties of materials?5 answersReverberant shear wave elastography (RSWE) can be used to study the mechanical properties of materials by evaluating their shear wave speed (SWS) and viscoelasticity. RSWE involves the generation of a reverberant shear wave field within the material, which propagates in all directions. The SWS of the material can be estimated using various techniques such as autocorrelation estimators, curve fitting, phase gradient, and convolutional neural networks. These estimators provide accurate measurements of SWS, allowing for the characterization of tissue stiffness and viscoelastic properties. RSWE has been successfully implemented in various imaging modalities, including ultrasound and optical coherence tomography, and has shown promising results in the elastic and viscoelastic characterization of tissues such as liver, cornea, and breast. The technique can be used to assess the uniformity of reverberant fields and detect regions with different mechanical properties. Overall, RSWE provides a valuable tool for studying the mechanical properties of materials and has potential applications in clinical settings.