Time-reversal techniques in ultrasound-assisted deep vein thrombosis treatment: Technology development and in vitro evaluation.

We describe a thrombolysis method that combines time-reversal acoustic (TRA) focusing with an AngioJet thrombectomy catheter to improve the dissolution of thrombus in the treatment of deep venous thrombosis (DVT). Commercially available ultrasound-assisted DVT systems have been shown to accelerate thrombolysis by up to 40% and reduce the amount of thrombolytic drug required for treatment by 50%–70%. Current ultrasound-assisted DVT treatments utilize a specially designed intravascular catheter with therapeutic ultrasound transducer on the tip and side. Additionally, MRI guided high intensity focused ultrasound systems have shown to rapidly lyse thrombus. We describe a novel TRA focusing system that is used to infuse fluids into the thrombus while simultaneously exposing the clot to safe levels of 1-MHz ultrasound energy. The system includes a combined infusion catheter-hydrophone, a ten-channel ultralow-output impedance amplifier, a broad-band ultrasound resonator, and MATLAB-based, TRA control and user-interface. TRA allows easy focusing of ultrasound therapy to the catheter tip from an external source, without complex phase-correction and array design. The system has been tested in vitro in a DVT phantom model, and results show that it provides 1-mm spatial resolution focusing. We present results in using TRA focusing to lyse bovine blood clots in the physiological size DVT phantom.