MRI-guided sonothrombolysis of rabbit carotid artery

Abstract

The potential of magnetic resonance imaging-guided focused ultrasound (MRgFUS) combined with the thrombolytic drug recombinant tissue plasminogen activator (rt-PA) to dissolve clots in the carotid of a New Zealand rabbit in vivo is evaluated. A spherically focused transducer of 5-cm diameter, focusing at 10 cm and operating at 1 MHz, was used. A pulsed ultrasound protocol was used that maintains a tissue temperature increase of less than 1 C in the clot (called safe temperature). MRgFUS has the potentials to dissolve clots that are injected in the carotid of rabbits in vivo. It was found that the time needed for opening the carotid artery using ultrasound and rt-PA was decreased compared with just using rt-PA. The time needed for opening the artery decreases with increasing acoustic intensity. With an intensity of 20 W/cm2 (spatial average temporal average), which is not causing artery heating, the time needed to completely open the artery was 70 minutes. The proposed protocol was monitored using magnetic resonance angiography every 1 minute.