Thresholds for the occurrence of acoustically induced cavitation in tissues: a re-examination of the evidence at therapeutic intensities and frequencies

Abstract

Current in vitro sonication experiments show immense variability in experimental set-ups and methods used. As a result, there is uncertainty in the ultrasound field parameters experienced by sonicated samples, poor reproducibility of these experiments and thus reduced scientific value of the results obtained. The scope of this narrative review is to briefly describe mechanisms of action of ultrasound, list the most frequently used experimental set-ups and focus on a description of factors influencing the outcomes and reproducibility of these experiments. The factors assessed include: proper reporting of ultrasound exposure parameters, experimental geometry, coupling medium quality, influence of culture vessels, formation of standing waves, motion/rotation of the sonicated sample and the characteristics of the sample itself. In the discussion we describe pros and cons of particular exposure geometries and factors, and make a few recommendations as to how to increase the reproducibility and validity of the experiments performed.