High frequency characterisation of commercial contrast agents

Commercial contrast agents are designed to resonate at low megahertz frequencies. This paper focuses on the high frequency characterisation of three contrast agents Definity (Bristol-Myers Squibb, N. Billerica, MA, USA), SonoVue (Bracco International, Milan Italy) and Optison (Amersham Health, UK). Three linear array probes (L8-16, L10-22, L16-28) from a Diasus ultrasound scanner (Dynamic Imaging, Livingston, UK) were mounted over a tank lined with an acoustic absorber. The contrast agents were diluted to 0.067% with water and gently agitated. The agent was insonated over a period of 90 seconds and the radiofrequency data from the first and last frame of insonation were digitised and analysed. A region-of-interest of 256 data points was selected at 12 rum depth and the mean backscafter power measured over the bandwidth of the transducers and normalised to the ultrasound data collected from a reference reflector.

The peak negative pressures were measured for each of the probes at a distance of 12 min from the transducer using a 0.2 mm active element membrane hydrophone.

Maximum mean backscatter power for all agents was obtained from the first frame of insonation using the L8-16 probe at maximum power output. The mean backscatter power decreased rapidly over the 90 second insonaton period suggesting rapid destruction of the agents.