Development of forward-looking ultrasound transducers for microbubble-aided intravascular ultrasound-enhanced thrombolysis

In this paper, we report the development of miniaturized forward-looking transducers for microbubble-mediated intravascular ultrasound-enhanced thrombolysis (UET). UET has shown its efficacy for thrombo-occlusive disease by enhancing penetration of thrombolytic drugs into clots, reducing the required dose. In this study, we adopted a previously-developed forward-looking, stacked type transducer for thrombolysis treatment with low dose (approximately 0.4 μg/ml)-recombinant tissue-plasminogen activator (rt-PA). The 650 kHz-prototype transducer with a concave lens enabled a confined ultrasound beam despite the small aperture (diameter <;1.5 mm) with respect to the wavelength (2.2 mm), and peak-negative-pressure of 1.35 MPa with a corresponding mechanical index of 1.67 was achieved. In vitro thrombolysis tests using the developed transducer with microbubble infusion showed that local administration of low dose-recombinant tissue-plasminogen activator (rt-PA) results in a two-fold increase in average thrombolytic rate versus without rt-PA.