Controlled Hyperthermia With High-Intensity Focused Ultrasound and Ultrasound Contrast Agent Microbubbles in Porcine...

Area of Science:

• Medical Imaging
• Acoustic Physics
• Biomedical Engineering

Background:

• High-intensity focused ultrasound (HIFU) is a non-invasive therapeutic technology.
• Microbubbles are used as contrast agents and to enhance ultrasound effects.
• Optimizing HIFU for targeted tissue heating is crucial for therapeutic applications.

Purpose of the Study:

• To investigate microbubble-enhanced temperature elevation using HIFU.
• To evaluate the effects of different acoustic pressures and injection methods (local vs. vascular).
• To assess HIFU-induced hyperthermia in ex vivo porcine liver under ultrasound guidance.

Main Methods:

• Ex vivo porcine liver samples (perfused and non-perfused) were used.
• High-intensity focused ultrasound (HIFU) was applied at varying acoustic pressures (0.6-3.5 MPa).
• Contrast microbubbles were administered via local or vascular injections, with temperature monitored by thermocouple and ultrasound imaging.

Main Results:

• At lower pressures (0.6-1.2 MPa) in non-perfused liver, microbubbles significantly increased temperature elevation via inertial cavitation.
• At higher pressures (2.4-3.5 MPa), tissue cavitation dominated, yielding similar temperature increases with or without injected microbubbles.
• Microbubble use consistently enlarged the heated area across all tested pressures.
• In perfused liver, only local microbubble injections achieved significant temperature enhancement.

Conclusions:

• Local microbubble injections optimize HIFU-induced hyperthermia by increasing microbubble concentration and heated area.
• This approach allows for greater temperature elevation at lower acoustic pressures, potentially reducing side effects.
• Microbubble-enhanced HIFU shows promise for targeted thermal therapies, particularly with localized administration.