Temperature change near microbubbles within a capillary network during focused ultrasound

Area of Science:

• Biomedical Engineering
• Acoustic Physics
• Medical Imaging

Background:

• Preformed gas bubbles enhance ultrasound energy absorption, suggesting their use in ultrasound treatments.
• In vivo studies show increased tissue temperature with bubbles, but microscopic temperature distribution remains uninvestigated.

Purpose of the Study:

• To simulate heat transfer between bubbles and tissue during focused ultrasound.
• To investigate the microscopic temperature distribution induced by microbubble oscillations.

Main Methods:

• Simulated microbubble oscillations within a rat cortical microvascular network.
• Used microbubble oscillation power density as input for the Pennes bioheat transfer equation.
• Mapped temperature solutions onto vascular data to create 3D temperature maps.

Main Results:

• Simulations showed high temperatures near bubbles and slow temperature rise in surrounding tissue.
• Heating increased with bubble frequency and insonation pressure, exhibiting a frequency-dependent peak.
• Induced temperature elevations were nonuniform, potentially impacting bio-effects.

Conclusions:

• Microbubble-induced heating is highly localized and dependent on frequency and pressure.
• Understanding these nonuniform temperature distributions is critical for effective therapeutic ultrasound planning.
• Further research can optimize bubble-enhanced ultrasound treatments by characterizing parameter effects.