Effect of Frequency-Dependent Attenuation on Predicted Histotripsy Waveforms in Tissue-Mimicking Phantoms

Tissue-mimicking phantoms are employed for the assessment of shocked histotripsy pulses in vitro. These broadband shock waves are critical for tissue ablation and are influenced by the frequency-dependent attenuation of the medium. The density, sound speed and attenuation spectra (2-25 MHz) were measured for phantoms that mimic key histotripsy targets. The influence of non-linear propagation relative to the attenuation was described in terms of Gol'dberg number. An expression was derived to estimate the bandwidth of shocked histotripsy pulses for power law-dependent attenuation. The expression is independent of the fundamental frequency of the histotripsy pulse for linear frequency-dependent attenuation.