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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http://dx.doi.org/10.1088/0031-9155/61/6/2582 | DOI Listing |
Ultrasonics
January 2025
Medical Ultrasound Department for the Suzhou Institute of Biomedical Engineering and Technology, Chinese Academy of Sciences, Suzhou, Jiangsu 215163, China. Electronic address:
Shear Wave Elastography (SWE) is an imaging technique that detects shear waves generated by tissue excited by Acoustic Radiation Force (ARF), and characterizes the mechanical properties of soft tissue by analyzing the propagation velocity of shear wave. ARF induces a change in energy density through the nonlinear propagation of ultrasound waves, which drives the tissue to generate shear waves. However, the amplitude of shear waves generated by ARF is weak, and the shear waves are strongly attenuated in vivo.
View Article and Find Full Text PDFThe eastern equatorial Atlantic hosts a productive marine ecosystem that depends on upward supply of nitrate, the primary limiting nutrient in this region. The annual productivity peak, indicated by elevated surface chlorophyll levels, occurs in the Northern Hemisphere summer, roughly coinciding with strengthened easterly winds. For enhanced productivity in the equatorial Atlantic, nitrate-rich water must rise into the turbulent layer above the Equatorial Undercurrent.
View Article and Find Full Text PDFJ Acoust Soc Am
January 2025
Department of Physics, Naval Postgraduate School, 833 Dyer Road, Monterey, California 93943-5216, USA.
The shear wave speed is often small compared to the compressional wave speed in the top part of the seabed, where acoustic normal modes penetrate. In sediments with weak but finite shear rigidity, the strongest conversion from compressional to shear waves occurs at interfaces within the sediment. Shear wave generation at such interfaces and interference within sediment layers lead to first-order perturbations in the normal mode phase speed and contributions to sound attenuation, which vary rapidly with frequency.
View Article and Find Full Text PDFUltrasound Med Biol
January 2025
Echosens, Paris, France.
Objective: Although FibroScan (FS), based on Vibration-Controlled Transient Elastography (VCTE), is a widely used non-invasive device for assessing liver fibrosis and steatosis, its current standard-VCTE examination remains timely and difficult on patients with obesity. The Guided-VCTE examination uses continuous shear waves to locate the liver by providing a real-time predictive indicator for shear wave propagation and uses shear wave maps averaging to increase the signal-to-noise ratio in difficult to assess patients. We aimed to evaluate the effectiveness of the new indicator, as well as compare examination times and success rates with both standard-VCTE and Guided-VCTE examinations.
View Article and Find Full Text PDFPolymers (Basel)
January 2025
Department of Mechanics of Materials and Constructions (MeMC), Vrije Universiteit Brussel, B-1050 Brussels, Belgium.
There is very limited research in the literature investigating the way acoustic emission signals change when polymer materials are undergoing different fracture modes. This study investigates the capability of acoustic emission to recognize the fracture mode through acoustic emission parameter analysis, and can be considered the first-ever study which examines the impact of different loading conditions, i.e.
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