Ultrasound-Guided Intravascular Sonothrombolysis With a Dual Mode Ultrasound Catheter: In Vitro Study

Thromboembolism in vessels often leads to stroke or heart attack and even sudden death unless brought under control. Sonothrombolysis based on ultrasound contrast agents has shown promising outcome in effective treatment of thromboembolism. Intravascular sonothrombolysis transducer was reported recently for unprecedented sonothrombolysis
in vitro
. However, it is necessary to provide an imaging guide during thrombolysis in clinical applications for optimal treatment efficiency. In this article, a dual mode ultrasound catheter was developed by combining a 16-MHz high-frequency element (imaging transducer) and a 220-kHz low-frequency element (treatment transducer) for sonothrombolysis
in vitro
. The treatment transducer was designed with a 20-layer PZT-5A stack with the aperture size of
$1.2\times1.2$
mm
²
, and the imaging transducer with the aperture size of
$1.2\times1.2$
mm
²
was attached in front of the treatment transducer. Both transducers were assembled into a customized 2-lm 10-Fr catheter.
In vitro
experiment was carried out using a bovine blood clot. Imaging tests were conducted, showing that the backscattering signals can be obtained with a high signal-to-noise ratio (SNR) for the 16-MHz imaging transducer. Sonothrombolysis was performed successfully that the volume of clot was reduced significantly after the 30-min treatment. The size changes of clot were observed clearly using the 16-MHz M-mode imaging during the thrombolysis. The findings suggest that the proposed ultrasound-guided intravascular sonothrombolysis can be enhanced since the position of treatment transducer can be adjusted with the target at the clot due to the imaging guide.