A 9-Fr Endovascular Therapy Transducer With an Acoustic Metamaterial Lens for Rapid Stroke Thrombectomy

Large vessel occlusion (LVO) stroke, in which major cerebral arteries such as the internal carotid and middle cerebral arteries supplying the brain are occluded, is the most debilitating form of acute ischemic stroke (AIS). The current gold standard treatment for LVO stroke is mechanical thrombectomy; however, initial attempts to recanalize these large, proximal arteries supplying the brain fail in up to 75% of cases, leading to repeated passes that decrease the likelihood of success and affect patient outcomes. We report the design, fabrication, and testing of a $3\times 3$ mm forward-treating ultrasound (US) transducer with an acoustic metamaterial lens to dissolve blood clots recalcitrant to first-pass mechanical thrombectomy in LVO stroke. Due to the lens with microscale features, the device was able to produce a $2.3\times $ increase in peak negative pressure (PNP) (4.3 versus 1.8 MPa) and $2.4\times $ increase in blood clot dissolution rate ( $5.43~\pm ~0.89$ versus $2.23~\pm ~0.41$ mg/min) with 90% mass reduction after 30 min of treatment. In this small endovascular form factor, the acoustic metamaterial lens increased the acoustic output from the transducer while minimizing the US energy delivered to the surrounding areas outside of the treatment volume.