title: Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles: simulation and experiment.
abstract: The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. 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 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse.
authors.affiliation: Institute of Biomedical Engineering, Kaunas University of Technology, Lithuania. adriana@cr.ktu.lt
authors.forename: Adriana
authors.initials: A
authors.lastname: Kvikliene
authors.forename: Rytis
authors.initials: R
authors.lastname: Jurkonis
authors.forename: Marcus
authors.initials: M
authors.lastname: Ressner
authors.forename: Lars
authors.initials: L
authors.lastname: Hoff
authors.forename: Tomas
authors.initials: T
authors.lastname: Jansson
authors.forename: Birgitta
authors.initials: B
authors.lastname: Janerot-Sjöberg
authors.forename: Arūnas
authors.initials: A
authors.lastname: Lukosevicius
authors.forename: Per
authors.initials: P
authors.lastname: Ask
mesh_terms: D003287:Contrast Media; D004452:Echocardiography; D008863:Microspheres; D008962:Models, Theoretical; D012815:Signal Processing, Computer-Assisted; D014159:Transducers
chemical_list: D003287:Contrast Media