Assessment of Cavitation From DEFINITY and DEFINITY RT

This study aimed to compare the size distributions of DEFINITY and DEFINITY RT microbubbles and to quantify their cavitation activity during infusion through a multi-sideport catheter in a flow phantom mimicking the human femoral vein exposed to 1.5 MHz therapeutic pulsed ultrasound.

Echo contrast agent size distributions were measured with an impedance-based particle counter before and after infusion through a multi-sideport catheter. The echo contrast agents were also insonified by 1.5 MHz ultrasound (1.0 MPa peak negative pressure, 10 Hz pulse repetition frequency, 3 ms pulse duration) after infusion in a 37°C circulating saline-filled flow phantom mimicking the human femoral vein. Passive cavitation imaging quantified stable and inertial cavitation activity during 30 min infusions.

The post-infusion number density of DEFINITY RT (3.8 ± 1.4 microbubbles/mL x10⁹) was approximately six times larger than non-expired DEFINITY (0.6 ± 0.2 microbubbles/mL x10⁹). DEFINITY RT (8.47 ± 0.99 µJ/mm³) exhibited a higher stable cavitation dose than both expired DEFINITY (3.33 ± 0.81 µJ/mm³) and non-expired DEFINITY (2.60 ± 0.63 µJ/mm³). The inertial cavitation dose for DEFINITY RT (7.881 ± 0.55 µJ/mm³) also exceeded both expired DEFINITY (1.48 ± 0.50 µJ/mm³) and non-expired DEFINITY (1.42 ± 0.13 µJ/mm³).

DEFINITY RT yielded the highest cavitation activity and non-expired DEFINITY spawned the least amount of cavitation. The observed differences further highlight that formulation and number density can affect the amount of stable and inertial cavitation activity.