Enhancement of static signal in large vessels using composite dual frequency pulses

A method for simultaneously pushing and imaging microbubbles is introduced. A programmable scanner with a broadband linear array was used to generate dual frequency pulses. For the range of flow velocities (2.65, 5.3, and 15.9 cm/s), microbubble concentrations (2.2 and 22 million/ml), and pushing frequencies (1.6, 3, 4, 6, 8 MHz), it was observed that the adherent microbubble signal in a 2 mm diameter vessel flow gelatin phantom reduced exponentially with increasing streaming velocities. Maximum adherent microbubble signal intensity was observed to scale with variations in the streaming microbubble concentration. The rate of increment in the adherent microbubble signal was found to be independent of the microbubble concentration. The adherent microbubble signal was maximized at the resonant frequency associated with the diameter corresponding to mean of the microbubble distribution. It was concluded that using the proposed dual frequency sequence, it may be feasible to use radiation force for optimizing the effect of targeted imaging and modulating drug delivery in large vessels with high shear rates.