Passive Cavitation Mapping by Cavitation Source Localization From Aperture-Domain Signals-Part I: Theory and Validation Through Simulations

Passive cavitation mapping (PCM) algorithms for diagnostic ultrasound arrays based on time exposure acoustics (TEA) exhibit poor axial resolution, which is in part due to the diffraction-limited point spread function of the imaging system and poor rejection by the delay-and-sum beamformer. In this article, we adapt a method for speed of sound estimation to be utilized as a cavitation source localization (CSL) approach. This method utilizes a hyperbolic fit to the arrival times of the cavitation signals in the aperture domain, and the coefficients of the fit are related to the position of the cavitation source. Wavefronts exhibiting poor fit to the hyperbolic function are corrected to yield improved sourcelocalization. We demonstrate through simulations that this method is capable of accurate estimation of the origin of coherent spherical waves radiating fromcavitation/pointsources. The average localization-error from simulated microbubble sources was 0.12 +/- 0.12mm (0.15 +/- 0.14 lambda(0) for a 1.78-MHz transmit frequency). In simulations of two simultaneous cavitation sources, the proposed technique had an average localization error of 0.2mm (0.23 lambda(0)), whereas conventionalTEAhad an average localization error of 0.81mm (0.97 lambda(0)). The reconstructed PCM-CSL image showed a significant improvement in resolution compared with the PCM-TEA approach.

Automated summary

Passive cavitation mapping (PCM) algorithms based on time exposure acoustics (TEA) exhibit poor axial resolution due to system limitations and rejection by the beamformer. A method for speed of sound estimation is adapted for cavitation source localization (CSL), improving source localization accuracy. The proposed technique shows significant improvement in resolution compared to conventional TEA.