Multi-band finite element simulation of ultrasound attenuation by soft tissue

The methods and results presented here test the ability of the multi-band finite element method to simulate the frequency dependence of attenuation of ultrasound within soft tissue like materials, and the potential translation of the approach from its previous applications in non-destructive testing into medical ultrasound. Using a variety of materials, the approach was tested by comparing the theoretical attenuation (based on the input attenuation constants and path length through the materials) to the attenuation of the signal energy within the simulation. In two models, hypothetical materials were devised, with arbitrary attenuation properties and acoustic impedance matched to a background with the density and sound speed of water. In the third model, acoustic impedance mismatches were introduced to simulate the signal energy loss due to reflection and attenuation as an ultrasound beam passes from water into parallel layers of human skin, fat and muscle. In all cases, the calculated signal loss (from the reflection coefficients and attenuation constants) agreed with the signal loss measured within the simulation to a high degree, reproducing the input parameters to four significant figures in all cases.