Noninvasive thrombolysis using histotripsy beyond the intrinsic threshold (microtripsy)

Area of Science:

• Biomedical Engineering
• Medical Physics
• Cardiovascular Research

Background:

• Histotripsy uses acoustic cavitation for noninvasive, image-guided thrombolysis.
• Traditional histotripsy with multi-cycle pulses risks vessel wall damage due to cavitation formation.
• Microtripsy, a new approach using single-cycle pulses, aims to confine cavitation within the vessel lumen.

Purpose of the Study:

• To investigate microtripsy for clot recanalization in an in vitro flow model.
• To test the hypothesis that microtripsy confines cavitation, preventing vessel wall contact.
• To evaluate the efficacy and safety of microtripsy in creating flow channels within clots.

Main Methods:

• Microtripsy applied using a 1-MHz transducer with single-cycle pulses (30 or 36 MPa peak negative pressure).
• Cavitation focus scanned through clots in a vessel phantom at 0.3 or 0.7 mm intervals.
• 3-D ultrasound imaging quantified channel dimensions; flow rates and debris particles were analyzed.

Main Results:

• Cavitation was consistently confined to the vessel lumen, avoiding vessel wall contact.
• Flow channels were successfully generated within clots, with diameters up to 60% of the vessel diameter.
• Restored flow rates reached up to 500 mL/min, with minimal (<10 μm) debris particles; 2 cm clots recanalized within 7 minutes.

Conclusions:

• Microtripsy demonstrates potential as a fast, precise, and effective noninvasive thrombolysis method.
• The technique successfully recanalizes clots by generating confined cavitation, minimizing risks of vessel damage and embolism.
• Optimizing parameters like peak negative pressure and scan interval enhances microtripsy's clot-busting capabilities.