Efficacy and safety of spot heating and ultrasound irradiation on in vitro and in vivo thrombolysis models

The feasibility of transcranial sonothrombolysis has been demonstrated, although little is known about the relationships between thermal or mechanical mechanisms and thrombolytic outcomes. Therefore, the present study aims to reveal the effect and safety of temperature and ultrasound through in vitro and in vivo thrombolysis models. Artificial clots in microtubes were heated in a water bath or sonicated by ultrasound irradiation, and then clots weight decrease with rising temperature and sonication time was confirmed. In the in vitro thrombotic occlusion model, based on spot heating, clot volume was reduced and clots moved to the distal side, followed by recanalization of the occlusion. In the in vivo study, the common carotid artery of rats was exposed to a spot heater or to sonication. No brain infarct or brain blood barrier disruption was shown, but endothelial junctional dysintegrity and an inflammatory response in the carotid artery were detected. The present spot heating and ultrasound irradiation models seem to be effective for disintegrating clots in vitro, but the safety of the in vivo model was not fully supported by the data. However, the data indicates that a shorter time exposure could be less invasive than a longer exposure.