Boiling Histotripsy Using Dual-Frequency Protocol on Murine Breast Tumor Model and Promotes Immune Activation.

Histotripsy is an ultrasound-guided, noninvasive, nonthermal ablation therapy that can mechanically lyse target tissues. There have been no reports of enhanced histotripsy for large-volume triple-negative breast cancer (TNBC). This study aims to verify the ability of a novel approach of dual-frequency mode combined with two-stage millisecond-length ultrasound pulses (DF-TS) to accelerate the treatment of murine subcutaneous 4T1 tumors and determine immune changes after treatment. A custom-designed 1.1-/2.2-MHz two-element confocal-annular array was used to treat approximately 6-mm tumors under ultrasound guidance and real-time monitoring. Two-stage millisecond-length ultrasound pulses were used to generate approximate cuboid ablation volumes (diagonal 5-6 mm) within each tumor, with a dose of 100 pulses/point. Immune effects were characterized by changes of pro-inflammatory cytokine levels and infiltration levels of immune cells. In all targeted treatment areas, bubble cloud activity was visualized by ultrasound monitoring. The novel protocol resulted in elliptical and controllable sized lesions, reducing the number of scanning points, and was generally well tolerated. After treatment, tumor growth experienced a seven-day stagnation period, the survival period of mice was prolonged, and the levels of pro-inflammatory cytokines and immune cell infiltration increased. This study demonstrates that DF-TS boiling histotripsy (BH) has a noninvasive, efficient, and precise ablation ability for TNBC and potentially enhances immune responses.

Ultrasound image segmentation using Gamma combined with Bayesian model for focused-ultrasound-surgery lesion recognition.

This study aims to investigate the feasibility of combined segmentation for the separation of lesions from non-ablated regions, which allows surgeons to easily distinguish, measure, and evaluate the lesion area, thereby improving the quality of high-intensity focused-ultrasound (HIFU) surgery used for the non-invasive tumor treatment. Given that the flexible shape of the Gamma mixture model (GΓMM) fits the complex statistical distribution of samples, a method combining the GΓMM and Bayes framework is constructed for the classification of samples to obtain the segmentation result. An appropriate normalization range and parameters can be used to rapidly obtain a good performance of GΓMM segmentation. The performance values of the proposed method under four metrics (Dice score: 85%, Jaccard coefficient: 75%, recall: 86%, and accuracy: 96%) are better than those of conventional approaches including Otsu and Region growing. Furthermore, the statistical result of sample intensity indicates that the finding of the GΓMM is similar to that obtained by the manual method. These results indicate the stability and reliability of the GΓMM combined with the Bayes framework for the segmentation of HIFU lesions in ultrasound images. The experimental results show the possibility of combining the GΓMM with the Bayes framework to segment lesion areas and evaluate the effect of therapeutic ultrasound.

Ultrasound-guidedin vivohistotripsy in rabbit kidneys using millisecond-length two-stage ultrasound pulses combined with fundamental and second harmonic superposition.

Objective.Histotripsy is a non-invasive focused ultrasound ablation method that can mechanically disintegrate tissues. This study aims to verify that ultrasound-guided histotripsy using millisecond-length two-stage ultrasound pulses combined with fundamental and second harmonic superposition can enhance treatment in rabbit kidneysin vivo. Approach.Rabbit kidneys (n = 10) were treated using a custom-designed 1.1/2.2 MHz two-element confocal-annular array, with lateral and axial full width at half-maximum pressure dimensions of approximately 1.0 and 6.0 mm. Two-stage ultrasound pulses were applied: stage 1 used 60-80 pulses with a pulse duration of 6 ms and a pulse repetition frequency of 10 Hz. Meanwhile, stage 2 consists of 2-4 periods, each period consists of a concentrated pulse train of localized high DC of 6% and an off-time of 3-5 s, with an average DC of 1%-1.5%. B-mode ultrasound imaging was used to guide and monitor the boiling and cavitation bubbles.Main results.Ultrasound-guided treatment was successful in all rabbits, and the ablation rate is about seven times that of single-frequency combined two-stage pulses, achieving enhanced histotripsy. The regular elliptical lesions with dimensions of 10.6 ± 0.8 mm × 3.9 ± 0.6 mm (axial × lateral) were generated, and a large-volume lesion was generated by multi-point treatment. The size of most lysates was about 2.5µm. Histologically, lesions were completely homogenized and well demarcated between treated-untreated areas. There was no apparent damage to critical structures surrounding lesions. Nonlinear simulations revealed that it may be the interaction between shock front and the cavitation and boiling bubbles generated by the dual-frequency effect enhanced the treatment efficiency.Significance.The novel histotripsy could improve treatment efficiency and generate regular elliptical lesions with controllable shape and axial dimensions, which may be a useful tool in treating renal cell carcinoma.

Non-Cavitation Targeted Microbubble-Mediated Single-Cell Sonoporation.

Sonoporation employs ultrasound accompanied by microbubble (MB) cavitation to induce the reversible disruption of cell membranes and has been exploited as a promising intracellular macromolecular delivery strategy. Due to the damage to cells resulting from strong cavitation, it is difficult to balance efficient delivery and high survival rates. In this paper, a traveling surface acoustic wave (TSAW) device, consisting of a TSAW chip and a polydimethylsiloxane (PDMS) channel, was designed to explore single-cell sonoporation using targeted microbubbles (TMBs) in a non-cavitation regime. A TSAW was applied to precisely manipulate the movement of the TMBs attached to MDA-MB-231 cells, leading to sonoporation at a single-cell level. The impact of input voltage and the number of TMBs on cell sonoporation was investigated. In addition, the physical mechanisms of bubble cavitation or the acoustic radiation force (ARF) for cell sonoporation were analyzed. The TMBs excited by an ARF directly propelled cell membrane deformation, leading to reversible perforation in the cell membrane. When two TMBs adhered to the cell surface and the input voltage was 350 mVpp, the cell sonoporation efficiency went up to 83%.