研發應用於磁振造影導引乳房腫瘤熱治療之高頻超音波環形陣列探頭

Abstract

高強度聚焦性超音波(High-Intensity Focused Ultrasound, HIFU)是利用聲波傳遞的特性達到非侵入式治療腫瘤的效果。本研究針對乳房腫瘤開發了一套高頻高強度聚焦性環形超音波換能器，期望能針對頂部的乳房腫瘤產生聚焦效果，而對底部的乳房腫瘤能施以熱治療。 在HIFU換能器的材料選擇方面，使用的是複合壓電陶瓷，其具有降低聲阻抗且提高機電耦合係數的優點；換能器的尺寸為半徑100mm、聚焦半徑100mm、高25mm、工作頻率為2.5MHz，且將其環形超音波換能器分成16個單元。換能器的特性方面，對其量測壓電係數d33、聲阻抗以及電聲轉換效率，來驗證換能器的輸出效率以及穩定性。 目前所開發的高頻超音波環形換能器無法有效將電功率轉換成聲功率，不能達到HIFU等級的加熱效果，但仍能對組織加溫。另外在仿體實驗結果證實此環形超音波換能器能將能量集中在直徑6 cm的水膠之中心位置。

High Intensity Focused Ultrasound (HIFU) can achieve a non-invasive treatment using sound wave transmission to heat the desired region. In this study, we tried to develop a ring-shaped HIFU transducer for breast tumors to generate thermal lesions in the tip region of the breast and to execute thermal therapy in the bottom of the breast. Using piezocomposite material for ultrasonic transducer can lower the acoustic impedance as well as increase the electro-mechanical coupling factor. The size of transducer is 100 mm in radius, 100 mm in radius of curvature, 25 mm in height and 2.5 MHz in working frequency. The transducer consists of 16 elements. To verify the output efficiency and stability, we measured the piezoelectric parameter d33, acoustic impedance and electro-acoustic efficiency. At the present, the high frequency ring-shaped ultrasound transducer cannot reach the requirements for a HIFU, while it can heat fresh pork tissues. This ultrasound transducer can transmit the acoustic power to the center of a 6 cm gelatin phantom to effectively raise the temperature.