Ultrastructural Analysis of Volumetric Histotripsy Bio-effects in Large Human Hematomas

Area of Science:

• Medical Devices
• Acoustic Technology
• Surgical Innovation

Background:

• Large soft tissue hematomas pose significant clinical challenges.
• Current treatments for hematomas are often painful and invasive.
• Pulsed high-intensity focused ultrasound (HIFU) histotripsy shows promise for non-invasive hematoma liquefaction.

Purpose of the Study:

• To assess the efficiency and speed of volumetric histotripsy for liquefying large human hematomas in vitro.
• To evaluate different histotripsy pulse parameters for optimal liquefaction.
• To determine the suitability of the resulting lysate for fine-needle aspiration.

Main Methods:

• Large human hematoma phantoms were created and treated with histotripsy using varying pulse durations (10, 2, and 0.4 ms) and amplitudes.
• Ultrasound guidance and a 1.5-MHz transducer were used for exposures.
• Liquefaction volume, speed, and lysate characteristics (cytology, ultrastructure) were analyzed.

Main Results:

• Histotripsy created uniform liquid-filled voids with sharp edges in all exposures.
• Liquefaction speed increased with shorter pulses and higher amplitudes, reaching up to 2.62 mL/min.
• Lysate analysis showed homogenized blood cells and fibrin fragments, with most <20 μm, suitable for aspiration.

Conclusions:

• Volumetric histotripsy is an effective and rapid method for in vitro human hematoma liquefaction.
• Shorter, higher-amplitude pulses enhance liquefaction speed.
• The resulting homogenized lysate is amenable to clinical fine-needle aspiration, reducing clogging risks.