Development of a Passive Cavitation Detector for Therapeutic Ultrasound Applications

• Main Authors: Chang, Hsin-Yun, 張馨云
• Other Authors: Chen, Jung-Chih
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/hh8hgq

碩士 === 國立交通大學 === 生醫工程研究所 === 107 === Acoustic cavitation has been shown to play key role in therapeutic ultrasound applications. Cavitation activity in High-Intensity Focus Ultrasound (HIFU) treatment significantly enhances the absorption of the acoustic energy, effectively accelerates heating the focal region in the tissue. And the bubbles activity of inertial cavitation tends to grow unstable, it may cause potentially undesirable focal damage. To ensure the safety, we endeavor to construct a real-time and low-cost Passive Cavitation Detection (PCD) for monitoring and controlling cavitation activity during HIFU treatmants. The goal of this study is to develop a PCD with high sensitivity and wide bandwidth. The transducer contains three parts, which are piezoelectric ceramic, matching layer, and a backing layer. Piezoelectric layer is PZT-5A. The matching layer is composed of anodic aluminum oxide (AAO) template filled with Epotek 301 epoxy, so that the piezoelectric with matching layer can match the acoustic resistance of water or tissue and improve the efficiency of sound energy conversion. In addition, Titanium is selected as a backing layer material and bonded to the piezoelectric layer. Titanium has a high acoustic impedance coefficient. It can absorb the sound waves radiated from the piezoelectric ceramic and reduce the influences of backing noise. Using the PiezoCAD simulation, it is known that this design can effectively improve the receiving bandwidth and sensitivity of PCD. The 1 MHz PCD developed by this research institute can effectively receive the cavitation effect signal induced by the 2 MHz HIFU transducer. It can determine whether there is a cavitation effect at different voltage outputs. Keyword: HIFU, Cavitation, Passive Cavitation Detection, Anodic Aluminum Oxide, PZT-5A