Oscillation of single microbubbles at room versus body temperature

The dynamic behavior of ultrasound contrast agents (UCAs) is normally studied at room temperature (~21degC) although clinical usage of the agents is at ~37degC. This paper investigates the influence of such temperature difference on the dynamic behavior of commercial agents SonoVue (Bracco) and Definity (Lantheus Medical Imaging). Using an in vitro optical setup, microbubbles were submersed in a water reservoir at room temperature or body temperature and insonified with 1.7 MHz ultrasound pulses having 10 kPa to 80 kPa amplitude. Radial excursion was resolved using the ultrafast-framing camera Brandaris-128. SonoVue microbubbles that were resonant (diameter ~4 mum) showed higher radial excursion at the higher temperature, up to a factor of 2. This factor was at most 1.5 for Definity. Both agents showed about 2-fold decrease of acoustic onset level when heated to body temperature.