Dual-beam histotripsy: a low-frequency pump enabling a high-frequency probe for precise lesion formation

Area of Science:

• Acoustics
• Biomedical Engineering
• Ultrasound Technology

Background:

• Histotripsy uses ultrasound pulses to fractionate tissue by generating bubble clouds.
• Bubble cloud formation depends on peak negative pressure exceeding a medium-specific threshold.
• Precise control over lesion generation is crucial for therapeutic applications.

Purpose of the Study:

• To investigate a dual-beam histotripsy method for precise lesion generation.
• To explore the use of a low-frequency pump pulse and a high-frequency probe pulse.
• To determine the feasibility of controlling lesion size and shape through pulse manipulation.

Main Methods:

• A dual-frequency (500-kHz and 3-MHz) array transducer was employed.
• Sub-threshold pump and probe ultrasound pulses were applied to phantoms and tissue.
• The constructive interference of peak negative pressures was analyzed.
• Lesion formation was observed based on varying pulse amplitudes and propagation directions.

Main Results:

• Dual-beam histotripsy successfully generated dense bubble clouds and lesions when pump and probe pulses constructively interfered above the threshold.
• The smallest reproducible lesion size was influenced by the relative amplitude of the pump and probe pulses, with a higher probe proportion yielding smaller lesions.
• Altering the probe pulse's propagation direction relative to the pump pulse modified the lesion shape.

Conclusions:

• The dual-beam histotripsy approach enables precise control over lesion generation by combining sub-threshold ultrasound pulses.
• This method is advantageous for treatments in highly attenuative and aberrative media, such as transcranial therapy, due to the pump pulse's robustness and the probe pulse's precision.
• The technique offers potential for targeted tissue ablation with improved accuracy and safety.