Chengzhi Shi - Ultrasound for Brain Imaging and Therapy

The development of acoustic metamaterials and the resulted manipulation of ultrasound wave propagation have led to many important technologies that can potentially be applied in medical diagnostics and therapy such as transcranial ultrasound, enhanced cavitation effect for histotripsy and thrombolysis, and noninvasive kidney stone management. In this talk, we will focus on two metamaterial applications in medical imaging and therapy: transcranial imaging enabled by non-Hermitian complementary acoustic metamaterial (NHCMM) and fast sonothrombolysis through vortex ultrasound induced shear stress. High-resolution transcranial imaging using noninvasive high-frequency ultrasound is challenging due to the impedance mismatch between skull and soft tissues and the intrinsic loss because of the porous skull. The development of active NHCMM can compensate the transmission loss resulting from both effects simultaneously that enhances transcranial transmission for high-resolution imaging. For the treatment of blood clots, sonothrombolysis has been demonstrated to be effective. However, the treatment usually last for more than 15 hours when treating a large clot, which is undesirable for the patient and surgeon and can sometimes become life threatening for severe cases of cerebral venous sinus thrombosis (CVST). The active metasurface generated vortex ultrasound induces contactless shear stress in the blood clot that drastically enhances fibrinolysis in blood clots that remarkably reduce the required treatment time with low risk of hemorrhage, especially in treating large, completely occluded, acute clots. Such capability makes the vortex ultrasound based endovascular sonothrombolysis a life-saving tool for severe cerebral venous sinus thrombosis, which has an increasing trend among young patients due to the COVID-19 pandemic.