Thesis (Ph.D.) - University of Toronto, 1981.
|Series||Report / University of Toronto Institute for Aerospace studies -- No.261|
Ultrasound Basics. February Nonlinear scattering by microbubble contrast agents provides a unique intravascular signature that can be distinguished from the echoes caused by surrouning. The cloud induces scattering, nonlinear distortion, and shielding of ultrasound, which increase the mechanical index in the pre-focal zone, shift the location, reduce the size, and modify the shape of the volume of tissue of high mechanical index values, and lower Author: Christian Vanhille, Kullervo Hynynen. Aug 06, · In order to study the changes in the TICs caused by changes in the MI, a detailed examination of the relationship between bubble behaviour and the driving ultrasound pressure is required. In this section, the nonlinear scattering behaviour of bubbles is examined, while nonlinear attenuation will be discussed in §§ and Cited by: T1 - Nonlinear ultrasound scattering by a cloud of microbubbles. AU - Silva, Glauber T. AU - Belohlavek, Marek. AU - McMahon, Eileen M. AU - Fatemi, Mostafa. PY - /1/1. Y1 - /1/1. N2 - In this study, we theoretically analyze the interaction of ultrasound waves in a liquid with suspended gas microbubbles confined in region of the eduevazquez.com: Glauber T. Silva, Marek Belohlavek, Eileen M. McMahon, Mostafa Fatemi.
Hence, in addition to the chemical properties of materials, the physical properties of the ultrasound emitted in the liquid must be considered in sonochemistry. In addition, bubbles in a liquid affect the physical properties determining sound propagation. The fundamentals underpinning the physics of ultrasound are presented in this chapter. Cited by: 3. This means that the bubble diameter is much smaller than the acoustic wavelength. Such bubbles are highly compressible and provide very high scattering cross sections. In the range of ultrasound peak pressure from kPA to 1 MPa the contrast agent backscatter shows nonlinear characteristics, such as emission of eduevazquez.com by: Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse. PMID: [Indexed for MEDLINE] MeSH termsCited by: The following effects are considered: nonlinear scattering at second harmonic and difference frequency in a single bubble, nonlinear determination of bubbles, nonlinear reverberation, parametric emission from a bubble layer and phase conjugation, effects of nonlinearity ‘concentration’ on acoustic wave eduevazquez.com by: 7.
Ultrasound in Medicine is a broad-ranging study of medical ultrasound, including ultrasound propagation, interaction with tissue, and innovations in the application of ultrasound in medicine. The book focuses specifically on the science and technology-the underlying physics and engineering. It examines the most closely related aspects of these basic sciences in clinical application and reviews 4/5(1). The nonlinear interaction of the ultrasound field and the bubble oscillations is considered. Results with and without bubbles for different void fractions of the cloud and different acoustic powers are compared. The cloud induces scattering, nonlinear distortion, and shielding of ultrasound, which increase the mechanical index in the pre-focal Author: Christian Vanhille, Kullervo Hynynen. Nonlinear Acoustics in Biomedical Ultrasound In many fields related to application of acoustic theory, the assumption of linear wave propagation is sufficient. In Biomedical ultrasound however, the propagation of sound waves is often accompanied by progressive wave distortion resulting from nonlinear, finite amplitude, effects. Nonlinear propagation of ultrasound through microbubble populations can generate artifacts and reduce contrast to tissue ratio in ultrasound imaging. The existing propagation model, which underestimates harmonic generation by an order of magnitude, was revised by incorporating a nonlinear constitutive equation for the coating into the description of the microbubble eduevazquez.com by: