An efficient treatment strategy for histotripsy by removing cavitation memory

Area of Science:

• Biomedical Engineering
• Acoustic Physics
• Ultrasound Therapy

Background:

• Cavitation memory effects, caused by persistent bubble nuclei, lead to uneven tissue fractionation in histotripsy.
• This inhomogeneity necessitates more pulses for complete tissue homogenization, reducing treatment efficiency.

Purpose of the Study:

• To investigate if removing cavitation memory by increasing pulse intervals (Δt) improves histotripsy treatment efficiency.
• To determine if randomizing cavitation bubble formation leads to more homogeneous tissue disruption.

Main Methods:

• Histotripsy treatments were performed on red blood cell phantoms and ex vivo livers.
• Varying pulse intervals (Δt) from 2 to 200 ms were used to passively remove cavitation memory.
• High-speed photography visualized cavitation patterns in phantoms; ex vivo livers validated findings in real tissues.

Main Results:

• Increasing Δt exponentially decreased correlation between successive cavitation patterns, indicating memory removal.
• Longer Δt significantly reduced the number of pulses required for complete lesion fractionation.
• Homogeneous tissue fractionation with defined lesion boundaries was achieved at Δt ≥ 100 ms in ex vivo livers.

Conclusions:

• Passive removal of cavitation memory by increasing pulse intervals enhances histotripsy efficiency.
• Longer pulse intervals promote homogeneous tissue fractionation, leading to improved therapeutic outcomes.
• This strategy offers a method for more controlled and effective ultrasound-based tissue ablation.