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Basic Acoustic Properties of Microbubbles
Author(s) -
De Jong Nico,
Bouakaz Ayache,
Frinking Peter
Publication year - 2002
Publication title -
echocardiography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 62
eISSN - 1540-8175
pISSN - 0742-2822
DOI - 10.1046/j.1540-8175.2002.00229.x
Subject(s) - harmonics , microbubbles , bubble , amplitude , acoustics , oscillation (cell signaling) , sound pressure , mechanics , radius , physics , nonlinear oscillations , scattering , harmonic , vibration , acoustic wave , acoustic resonance , fundamental frequency , nonlinear acoustics , nonlinear system , optics , resonance (particle physics) , ultrasound , atomic physics , chemistry , biochemistry , computer security , quantum mechanics , voltage , computer science
Small (encapsulated) gas bubbles in a contrast medium react to an external oscillating pressure field with volume pulsations. Depending on the magnitude of the ultrasound wave, the vibrations will be related either linearly or nonlinearly to the applied acoustic pressure. For low acoustic pressures, the instantaneous radius oscillates linearly in relation to the amplitude of the applied external pressure field. The oscillation of the bubble is governed by parameters such as resonance frequency, damping coefficients, and shell properties. For higher amplitudes of the external field, the pulsation of the bubbles becomes nonlinear. The spectrum of the scattered ultrasound wave also contains higher harmonics of the emitted frequency in addition to the fundamental frequency. The emitted frequency, bubble size, and nonlinear propagation effects have significant influence on the harmonic generation. For encapsulated bubbles exposed to even higher acoustic amplitudes, their scattering effectiveness increases dramatically and becomes transient. The scattered frequency spectrum broadens, containing higher harmonics. This consequence is due to rupture, disappearance, change of gas content, etc. Using these specific characteristics of the contrast bubbles will open new perspectives in imaging and analysis for medical diagnosis.