Triple function IVUS: Diagnostic imaging, radiation force, and therapeutic for microbubble-based drug delivery

A prototype triple function intravascular ultrasound (IVUS) catheter, providing three operating frequencies, was designed, fabricated, and tested. The prototype was characterized by collecting one way acoustic output and beam profiles. The elongated acoustic radiation force (ARF) element has a center frequency of 3.6 MHz and a -6 dB fractional bandwidth of 38%. The therapeutic and imaging element (TIE) has a center frequency of 9 MHz and -6 dB fractional bandwidth of 47% with a width mode resonance of 1.9 MHz. The maximum recorded peak negative pressure at 1.5 MHz was 600kPa for the TIE. The displacement of microbubbles due to the ARF element was optically measured and compared to a 1-D microbubble displacement model. Average microbubble velocities of up to 0.6 m/s were measured using a single 280 kPa 20 cycle 3 MHz Gaussian ramped sinusoidal pulse. A wire target was imaged with the IVUS prototype in a wall-less flow phantom.