We aim to develop a nanodroplet (ND)-mediated intravascular ultrasound (US) transducer for deep vein thrombosis treatments. The US device, having an efficient forward directivity of the acoustic beam, is capable of expediting the clot dissolution rate by activating cavitation of NDs injected onto a thrombus. We designed and prototyped a multi-pillar piezoelectric stack (MPPS) transducer composed of four piezoelectric stacks. Each stack was made of five layers of PZT-4 plates, having a dimension of 0.85 × 0.85 × 0.2 mm³. The transducer was characterized by measuring the electrical impedance and acoustic pressure, compared to simulation results. Next, in-vitro tests were conducted in a blood flow mimicking system using the transducer equipped with an ND injecting tube. The miniaturized transducer, having an aperture size of 2.8 mm, provided a high mechanical index of 1.52 and a relatively wide focal zone of 3.4 mm at 80 V_pp, 0.96 MHz electric input. The mass-reduction rate of the proposed method (NDs + US) was assessed to be 4.1 and 4.6 mg/min with and without the flow model, respectively. The rate was higher than that (1.3–2.7 mg/min) of other intravascular ultrasound modalities using micron-sized bubble agents. The ND-mediated intravascular sonothrombolysis using MPPS transducers was demonstrated with an unprecedented lysis rate, which may offer a new clinical option for DVT treatments. The MPPS transducer generated a high acoustic pressure (~3.1 MPa) at a distance of approximately 2.2 wavelengths from the small aperture, providing synergistic efficacy with nanodroplets for thrombolysis without thrombolytic agents.

我们的目标是开发一种纳米液滴（ND）介导的血管内超声（US）换能器，用于深静脉血栓形成的治疗。 US 装置具有有效的声束前向方向性，能够通过激活注射到血栓上的 ND 的空化来加快血栓溶解速度。我们设计并制作了由四个压电堆栈组成的多柱压电堆栈 (MPPS) 传感器原型。每个堆叠由五层 PZT-4 板制成，尺寸为 0.85 × 0.85 × 0.2 mm ³ 。通过测量电阻抗和声压并与仿真结果进行比较来表征换能器。接下来，使用配备 ND 注射管的传感器在血流模拟系统中进行体外测试。该小型化传感器的孔径尺寸为 2.8 mm，在 80 V _pp 、0.96 MHz 电输入下提供了 1.52 的高机械指数和 3.4 mm 的相对较宽的焦区。所提出的方法（NDs + US）的质量减少率在有和没有流动模型的情况下分别评估为 4.1 和 4.6 mg/min。该速率高于使用微米级气泡剂的其他血管内超声模式（1.3-2.7 毫克/分钟）。使用 MPPS 换能器的 ND 介导的血管内声溶栓具有前所未有的溶解率，这可能为 DVT 治疗提供新的临床选择。 MPPS 换能器在距小孔径约 2.2 个波长的距离处产生高声压（约 3.1 MPa），与纳米液滴在无需溶栓剂的情况下提供溶栓协同功效。