Transient cavitation in tissues during ultrasonically induced hyperthermia

Area of Science:

• Medical physics
• Biomedical engineering
• Oncology

Background:

• Hyperthermia therapy uses heat to treat cancer.
• Ultrasonic heating is a method for hyperthermia.
• Understanding cavitation during ultrasonic heating is crucial for safety and efficacy.

Purpose of the Study:

• To investigate transient cavitation in tissues during ultrasonic hyperthermia.
• To determine the power thresholds for cavitation in tissues.

Main Methods:

• Utilized an isospherical array of ultrasonic transducers for hyperthermia.
• Conducted in vitro and in vivo studies.
• Detected transient cavitation by identifying the first half-order subharmonic of ultrasound.

Main Results:

• Transient cavitation was confirmed in tissues during ultrasonic heating.
• Cavitation thresholds in tissue required 75 +/- 8 W/cm2 applied power.
• This power level exceeds that needed for therapeutic hyperthermia (43-45°C).

Conclusions:

• Transient cavitation occurs in tissues during clinical ultrasonic hyperthermia.
• Higher power levels are needed to induce cavitation than for therapeutic heating.
• Further research may be needed to mitigate cavitation effects during treatment.