Effects of frequency on bubble-cloud behavior and ablation efficiency in intrinsic threshold histotripsy

Abstract

Objective. Histotripsy is a non-thermal focused ultrasound ablation method that destroys tissue through the generation of a cavitation bubble cloud. Previous work studying intrinsic threshold histotripsy has shown that dense bubble clouds can be formed by a single-cycle pulse when the negative pressure exceeds an intrinsic threshold of ∼25–30 MPa, with the ablation efficiency dependent upon the size and density of bubbles within the cloud. This work investigates the effects of frequency on bubble-cloud behavior and ablation efficiency in intrinsic threshold histotripsy. Approach. A modular transducer was used to expose agarose tissue phantoms to 500 kHz, 1 MHz, or 3 MHz, histotripsy pulses. Optical imaging was used to measure the bubble-cloud dimensions, bubble density, and bubble size. The effects of frequency on ablation efficiency were also investigated by applying histotripsy to red blood cell (RBC) phantoms. Main results. Results revealed that the bubble-cloud size closely matched theoretical predictions for all frequencies. The bubble density, which is a measure of the number of bubbles per unit area, was shown to increase with increasing frequency while the size of individual bubbles within the cloud decreased at higher frequencies. Finally, RBC phantom experiments showed decreasing ablation efficiency with increasing frequency. Significance. Overall, results demonstrate the effects of frequency on histotripsy bubble-cloud behavior and show that lower frequency generates more efficient tissue ablation, primarily due to enhanced bubble expansion.

Experimental and Computational Investigation of Clustering Behavior of Cyclodextrin–Perfluorocarbon Inclusion Complexes as Effective Histotripsy Agents

“…However, it is worth noting that PFH-containing NCCs formed more well-defined, dense, and localized bubble clouds, whereas PFP-containing NCCs had a more scattered cavitation outside of the main bubble cloud, particularly under the 1:1 ratio condition. This finding indicates that PFH-containing NCCs are better candidates for generating precise and efficient NMH ablation. , It should also be noted that βCD PFH NCCs with the 1:1 ratio display a bubble behavior comparable to that of the 1:5 analogue, demonstrating that both combinations result in effective agents for generating well-defined, dense, and precise histotripsy bubble clouds that are needed for the precise ablation of tissues using NMH. , …”

“…This finding indicates that PFH-containing NCCs are better candidates for generating precise and efficient NMH ablation. 13,50 It should also be noted that βCD PFH NCCs with the 1:1 ratio display a bubble behavior comparable to that of the 1:5 analogue, demonstrating that both combinations result in effective agents for generating well-defined, dense, and precise histotripsy bubble clouds that are needed for the precise ablation of tissues using NMH. 13,50 ■ CONCLUSIONS This study investigated computationally and experimentally the interaction of 8 CD with 2 PFC derivatives to discover the most efficient NMH agents.…”

“…13,50 It should also be noted that βCD PFH NCCs with the 1:1 ratio display a bubble behavior comparable to that of the 1:5 analogue, demonstrating that both combinations result in effective agents for generating well-defined, dense, and precise histotripsy bubble clouds that are needed for the precise ablation of tissues using NMH. 13,50 ■ CONCLUSIONS This study investigated computationally and experimentally the interaction of 8 CD with 2 PFC derivatives to discover the most efficient NMH agents. Initially, computational investigations were performed to understand the inclusion complex formation of each CD derivative with either of the PFCs, and it was concluded that all CD derivatives form inclusion complexes with PFCs, except αCD and HMγCD.…”

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.…”

Research progress and clinical evaluation of histotripsy: a narrative review

“…The size and the degree of the ablation applied to lesions produced by cavitation cloud histotripsy, along with its therapeutic efficacy, depend on pulse duration, operating frequency, PRF, and the number of pulses (32)(33)(34). Under high PRF conditions, the pulse interval is shorter than the time taken for bubble dissolution (21,23).…”