Cavitation radiated energy density (CRED): An energy-preserving spatiotemporal cavitation dose metric

Passive Acoustic Mapping (PAM) makes it possible to qualify and quantify the spatio-temporal distribution of cavitation activity during therapeutic ultrasound treatments, in addition to providing a valuable tool for real-time treatment monitoring and cavitation imaging. To enable meaningful correlation of cavitation activity with the safety and efficacy of associated bioeffects, a cavitation dose metric is required that is energy-preserving, device-independent and adequately normalized to the tissue volume being affected by the reported cavitation activity. We introduce cavitational radiated energy density (CRED), defined as the total energy of either narrowband or broadband radiated acoustic emissions over a volume, divided by that volume. We show that image blurring caused by the instrumentation-dependentpoint spread function introduces significant image artifacts and CRED errors when using existing conventional and adaptive beamformers, and propose a novel PAM algorithm that utilizes the Lucy–Richardson deconvolution (LRD) technique to compensate for the point-spread function and thus provide cavitation maps with reduced tail artifacts and improved energy estimates in a computationally efficient manner. Using a combination of modeling and experimental approaches, we demonstrate the quantitative significance of CRED and the potential of the LRD-PAM algorithm to enable energy-preserving quantitative real-time monitoring of cavitation-based therapies, independently of the instrumentation employed.