The histotripsy spectrum: differences and similarities in techniques and instrumentation

Area of Science:

• Biomedical Engineering
• Acoustic Physics
• Medical Devices

Background:

• Histotripsy is a non-thermal mechanical tissue ablation technique developed over the past two decades.
• It utilizes focused ultrasound pulses to induce bubble activity and acoustic streaming for tissue fractionation.

Purpose of the Study:

• To review the differences and similarities in physical mechanisms and bioeffects of various histotripsy methods.
• To correlate these mechanisms with optimal instrumentation and target clinical applications.

Main Methods:

• Comparison of four histotripsy methods: intrinsic threshold, shock-scattering, hybrid, and boiling histotripsy.
• Analysis of pulse duration (microseconds to milliseconds), ultrasound waveform, and acoustic pressures.
• Examination of the role of nonlinear propagation effects and shock waves.

Main Results:

• All histotripsy methods use focused ultrasound at low duty cycles to create bubble activity and acoustic streaming.
• Key differences lie in pulse duration, waveform, and required acoustic pressures.
• Instrument design (electronics, transducer characteristics) is dictated by the specific histotripsy method's requirements.

Conclusions:

• Optimized instrumentation combined with specific bioeffects enables targeted clinical applications for each histotripsy variant.
• Understanding the physical mechanisms is crucial for advancing histotripsy technology and its therapeutic uses.