Resonance frequency of microbubbles in small blood vessels

Ultrasound contrast agents have the potential to be used for selective tissue and cell targeting, because they act as localized acoustic energy absorbers and emitters. Gas bubbles are more active as acoustic energy absorbers when they work at their natural oscillation frequency. Mathematical modeling suggests that the resonance frequency is strongly affected by the presence of boundaries represented by the blood vessel and it is in general lower than its free value. When microbubbles operate at their natural frequency, they absorb, and therefore emit, more energy. This localized energy may be used for many therapeutic purposes. The knowledge of the resonance frequency may allow specific diameter vessels to be targeted with minimal impact on the other vessels and surrounding tissues.