Integration of a dual-mode catheter for ultrasound image guidance and HIFU ablation using a 2-D CMUT array

Image-guided high-intensity focused ultrasound (HIFU) is widely used not only for non-invasive therapy but also for a precise approach for tissue ablation. Most HIFU systems use piezoelectric transducers, which are typically bulky due to active cooling, and separate imaging and HIFU transducers, and are therefore impractical for catheter-based applications. Taking advantage of a single 2-D capacitive micromachined ultrasonic transducer (CMUT) array, we developed a dual-mode catheter that can switch between ultrasound imaging mode and HIFU ablation mode. The catheter is equipped with an application-specific integrated circuit (ASIC) and a 32 × 32-element 2-D CMUT array. Both ASIC and CMUT are flip-chip bonded to a custom-designed flexible printed circuit board (flex PCB) via 100-μm and 80-μm solder balls. Then, the flex legs are folded and terminated with pads for a micro zero insertion force (μZIF) connector, allowing easy assembly replacement without the extra cost of coaxial cable assembly. Next, the micro-coaxial cables are assembled at the end of the μZIF connectors. After integration with a 3-D printed tip and encapsulating with polydimethylsiloxane (PDMS), the catheter is finalized in a 22-mm diameter shaft. We successfully validated the functionality of both modes of the dual-mode catheter in oil. We are currently preparing the test for an animal study.

影像引导高强度聚焦超声（HIFU）不仅广泛用于非侵入性治疗，还用于组织消融的精确方法。大多数HIFU系统使用压电换能器，由于主动冷却，其通常体积庞大，并且成像和HIFU换能器是分开的，因此对于基于导管的应用不实用。利用单个二维电容式微加工超声换能器（CMUT）阵列，我们开发了一种双模导管，它可以在超声成像模式和HIFU消融模式之间切换。该导管配备有专用集成电路（ASIC）和一个32×32元件的二维CMUT阵列。ASIC和CMUT都通过100μm和80μm的焊球倒装芯片键合到定制设计的柔性印刷电路板（柔性PCB）上。然后，将柔性引脚折叠并用微零插入力（μZIF）连接器的焊盘端接，从而无需同轴电缆组装的额外成本即可轻松进行组装更换。接下来，将微同轴电缆组装在μZIF连接器的末端。在与3D打印的尖端集成并用聚二甲基硅氧烷（PDMS）封装后，导管最终制成直径为22mm的轴。我们在油中成功验证了双模导管两种模式的功能。我们目前正在为动物研究准备测试。