Simulation of ultrasonic pulse propagation through the abdominal wall
- 1 August 1997
- journal article
- research article
- Published by Acoustical Society of America (ASA) in The Journal of the Acoustical Society of America
- Vol. 102 (2) , 1177-1190
- https://doi.org/10.1121/1.421015
Abstract
Ultrasonic pulse propagation through the human abdominal wall has been simulated using a model for two-dimensional propagation through anatomically realistic tissue cross sections. The time-domain equations for wave propagation in a medium of variable sound speed and density were discretized to obtain a set of coupled finite-difference equations. These difference equations were solved numerically using a two-step MacCormack scheme that is fourth-order accurate in space and second-order accurate in time. The inhomogeneous tissue of the abdominal wall was represented by two-dimensional matrices of sound speed and density values. These values were determined by processing scanned images of abdominal wall cross sections stained to identify connective tissue, muscle, and fat, each of which was assumed to have a constant sound speed and density. The computational configuration was chosen to simulate that of wavefront distortion measurements performed on the same specimens. Qualitative agreement was found between those measurements and the results of the present computations, indicating that the computational model correctly depicts the salient characteristics of ultrasonic wavefront distortion in vivo. However, quantitative agreement was limited by the two-dimensionality of the computation and the absence of detailed tissue microstructure. Calculations performed using an asymptotic straight-ray approximation showed good agreement with time-shift aberrations predicted by the full-wave method, but did not explain the amplitude fluctuations and waveform distortion found in the experiments and the full-wave calculations. Visualization of computed wave propagation within tissue cross sections suggests that amplitude fluctuations and waveform distortion observed in ultrasonic propagation through the abdominal wall are associated with scattering from internal inhomogeneities such as septa within the subcutaneous fat. These observations, as well as statistical analysis of computed and observed amplitude fluctuations, suggest that weak fluctuation models do not fully describe ultrasonic wavefront distortion caused by the abdominal wall.Keywords
This publication has 31 references indexed in Scilit:
- Measurements of ultrasonic pulse distortion produced by human chest wallThe Journal of the Acoustical Society of America, 1997
- A numerical method for general finite amplitude wave propagation in two dimensions and its application to spark pulsesThe Journal of the Acoustical Society of America, 1991
- Direct estimation of aberrating delays in pulse-echo imaging systemsThe Journal of the Acoustical Society of America, 1990
- Phase aberration correction in medical ultrasound using speckle brightness as a quality factorThe Journal of the Acoustical Society of America, 1989
- Estimates of wave front distortion from measurements of scattering by model random media and calf liverThe Journal of the Acoustical Society of America, 1989
- Characterization of volume scattering power spectra in isotropic media from power spectra of scattering by planesThe Journal of the Acoustical Society of America, 1983
- Adaptive ultrasonic array imaging system through an inhomogeneous layerThe Journal of the Acoustical Society of America, 1982
- Compilation of empirical ultrasonic properties of mammalian tissues. IIThe Journal of the Acoustical Society of America, 1980
- Atmospheric Correction Factor for Sonic-Boom Pressure AmplitudesThe Journal of the Acoustical Society of America, 1969
- The diffraction of radio waves in passing through a phase-changing ionosphereProceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences, 1951