Interaction of Microbubbles with Ultrasound

Area of Science:

• Cardiology
• Biomedical Engineering
• Medical Imaging

Background:

• Clinical need for bedside myocardial perfusion studies is high.
• Microbubbles are investigated as intravascular tracers for echocardiography-based perfusion imaging.
• Understanding microbubble-acoustic field interactions is crucial for optimizing this technique.

Purpose of the Study:

• To elucidate the complex interactions of microbubbles within an acoustic field for echocardiography.
• To evaluate different echocardiographic imaging modalities for myocardial perfusion assessment using microbubbles.
• To determine the most promising technique for reproducible myocardial perfusion evaluation.

Main Methods:

• Investigated microbubble behavior under varying acoustic pressures (low, medium, high).
• Compared traditional gray scale, second harmonic, and harmonic power Doppler echocardiography.
• Evaluated pulse inversion imaging with stabilized microbubbles (SonoVue trade mark) in vitro.

Main Results:

• Microbubble signal intensity depends on acoustic pressure, showing linear backscatter, harmonic resonance, and spontaneous acoustic emission.
• Second harmonic imaging showed some success but faced challenges with signal overlap.
• Harmonic power Doppler was sensitive but limited by attenuation.
• Pulse inversion imaging demonstrated superiority over harmonic power Doppler in vitro.

Conclusions:

• Microbubble interactions with acoustic fields are pressure-dependent and complex.
• Pulse inversion imaging shows significant potential for sensitive and robust myocardial perfusion assessment.
• Further human studies are required to establish myocardial contrast echocardiography as a reproducible diagnostic technique.