Bubble-Induced Color Doppler Feedback for Histotripsy Tissue Fractionation

Area of Science:

• Medical Physics
• Biomedical Engineering
• Acoustic Medicine

Background:

• Histotripsy therapy uses high-intensity ultrasound pulses to create cavitation bubble clouds, leading to tissue fractionation and liquefaction.
• Following cavitation, the coherent motion of residual nuclei can be detected using ultrasound color Doppler acquisitions.

Purpose of the Study:

• To investigate the characteristics of cavitation residual nuclei motion as real-time feedback for histotripsy tissue fractionation.
• To establish the correlation between bubble-induced color Doppler (BCD) metrics and the progression of histotripsy treatment.

Main Methods:

• Three experiments were conducted using agarose tissue phantoms and ex vivo porcine liver.
• Bubble-induced color Doppler (BCD) and particle image velocimetry (PIV) were used to monitor residual cavitation nuclei motion.
• Red blood cells (RBCs) were incorporated to quantify fractionation, and histological analysis validated BCD feedback in liver tissue.

Main Results:

• Both BCD and PIV demonstrated chaotic followed by coherent motion of residual nuclei, with velocity measurements showing good agreement.
• A monotonic increase in rebound time was observed with increased therapy dose, up to a saturation point.
• A strong linear correlation was found between RBC fractionation level and BCD peak rebound velocity, and similarly between BCD metrics and histological fractionation in liver.

Conclusions:

• Bubble-induced color Doppler (BCD) provides quantitative, real-time feedback on histotripsy treatment progression.
• The observed correlations suggest BCD is a valuable tool for monitoring and potentially guiding histotripsy therapies.