Microbubble ultrasound contrast agent (UCA)

Microbubble ultrasound contrast agents are suspensions of gas-filled microbubbles (typically perfluorocarbon, sulfur hexafluoride, or nitrogen) encapsulated within shells made from lipids, proteins, or polymers. When injected intravenously, they remain confined within the vascular system due to their size, behaving as intravascular contrast agents. Upon exposure to ultrasound waves, microbubbles undergo volume oscillations at diagnostic frequencies (1–15 MHz), resonating and emitting sound at harmonic and sub-harmonic frequencies. The dramatic acoustic impedance mismatch between the gas in the microbubble and surrounding blood/tissue yields strong nonlinear reflection and scattering, greatly enhancing blood pool visualization by ultrasound. Higher acoustic pressure can cause inertial cavitation, leading to rapid bubble collapse and possible tissue microinjury, which is being explored therapeutically but carries safety considerations. These agents do not represent molecular targets for drug action but are increasingly used for molecular imaging and targeted delivery applications.

Other names

microbubble contrast agentultrasound microbubbleultrasound contrast microbubbleCEUS agent (contrast-enhanced ultrasound agent)