Bubble Cloud Behavior and Ablation Capacity for Histotripsy Generated from Intrinsic or Artificial Cavitation Nuclei

Abstract

The study described here examined the effects of cavitation nuclei characteristics on histotripsy. Highspeed optical imaging was used to compare bubble cloud behavior and ablation capacity for histotripsy generated from intrinsic and artificial cavitation nuclei (gas-filled microbubbles, fluid-filled nanocones). Results showed a significant decrease in the cavitation threshold for microbubbles and nanocones compared with intrinsic-nuclei controls, with predictable and well-defined bubble clouds generated in all cases. Red blood cell experiments showed complete ablations for intrinsic and nanocone phantoms, but only partial ablation in microbubble phantoms. Results also revealed a lower rate of ablation in artificial-nuclei phantoms because of reduced bubble expansion (and corresponding decreases in stress and strain). Overall, this study demonstrates the potential of using artificial nuclei to reduce the histotripsy cavitation threshold while highlighting differences in the bubble cloud behavior and ablation capacity that need to be considered in the future development of these approaches.

Particle-Mediated Histotripsy for the Targeted Treatment of Intraluminal Biofilms in Catheter-Based Medical Devices

“…Although a small reduction in bacteria was seen with PMH, it should be noted that a clinically significant reduction in viable bacteria is on the order of 2 to 3 magnitudes, which was not 8 BME Frontiers achieved using the treatment parameters in this study and should be investigated more in future studies. It is possible that the lower pressures used in PMH may have reduced the bactericidal effects of the treatment compared to conventional histotripsy at higher pressures, which would be consistent with prior studies showing a decrease in histotripsy ablation efficiency for PMH methods tested in red blood cell tissue phantoms, likely due that to reduced bubble expansion at the lower pressure levels [33]. When compared with data from our previous work with conventional histotripsy, PMH at a p − of 12.3 MPa showed less bactericidal activity after 1 scan than what was observed for conventional histotripsy at a higher pressure of 47.6 MPa [15].…”

Growth and Collapse of an Isolated Bubble Driven by a Single Negative Histotripsy Cycle in Agarose Gel: Stress, Strain, and Strain Rate Fields

“…Until our work integrating single-bubble dynamics modeling and cavitation experiments to determine viscoelastic properties at high rates [29], previous studies [23], [30], [36] had to rely on values originating from quasi-static measurements. An additional modeling uncertainty pertaining to the composition of the material is the initial radius sizeor the nucleus/nidus size, as evidenced by the wide range of values assumed for histotripsy bubbles in different media [23], [47], [48]. Our choice to initialize our simulations using the stress-free radius is consistent with past observations that the gel is likely to fracture due to the large stretch during explosive bubble growth [30]; we note that the calculated stresses and strains are dependent upon this quantity.…”

DNA Release from Complex Plant Tissue using Focused Ultrasound Extraction (FUSE)

“…For all focused ultrasound experiments, high-speed optical imaging was done using a machine- vision camera (Blackfly S 3.2MP Mono USB3 Vision, FLIR Integrated Imaging Solutions, Richmond, BC, Canada) that was aligned with the focal zone of the transducer using a 100 mm F2.8 Macro lens (Tokina AT-X Pro, Kenko Tokina Co., LTD, Tokyo, Japan) and backlit by a custom- built pulsed LED strobe light capable of high-speed triggering with 1 µs exposures. As done in previous studies, the camera and the strobe light were triggered individually by the amplifier box, with the camera shutter opening at the time of pulse generation and the strobe acting as the shutter [27, 28]. The camera was triggered to capture one image every 50 th pulse.…”