Here’s My Two Cents… Low-cost, Acoustically Transparent Containers Allow Quantification of Cavitation Energy in Vitro

As cavitation-based therapies continue to enter the clinic, there is growing demand for methods to quantify the energy released by cavitating bubbles. Passive Acoustic Mapping (PAM) can reconstruct the energy and distribution of cavitation from multi-sensor recordings of bubble emissions, but its accuracy is impaired in vitro by the aberrating presence of a sample container between the cavitating media (nuclei/cells/tissues) and detectors. To our knowledge, the effects of these vessels on PAM have never been studied. Additionally, the typical need for sterility and a large number of samples makes low cost essential for sample containers in cavitation experiments. Here, we characterize the effects of common laboratory vessels in the range 3–14 MHz via an acoustic reciprocity experiment, then describe the design and testing of a novel container with improved acoustic transparency. The new device reduced worst-case magnitude and phase errors by 13.7 dB and 6.6 radians respectively, compared to ordinary 2 ml centrifuge tubes. We will also present quantitative measures of container effects on PAM energy measurement and localization. The new containers are manufactured from 100 micron polymer film via vacuum forming, are quick and easy to make in any shape in a normal laboratory, and cost US$0.02 each.