應用於超音波熱治療之多陣元聚焦換能器及溫度控制器設計

Design of a Multi-Element Ultrasound Transducer and a Temperature Controller for HIFU Thermal Therapy

邱俊彥(Chun-Yen Chiu)

指導教授 ： 朱堃誠

義守大學/醫學院/生物醫學工程學系/碩士(2016年)

摘要

高強度聚焦超音波(HIFU)為非侵入式腫瘤治療的一種手段，其是利用超音波的聚焦特性將能量聚焦到腫瘤細胞，使細胞產生瞬間高溫，造成不可逆的破壞而達到治療效果。為使得超音波產生合理聚焦，本研究設計一多陣元超音波幾何聚焦系統，利用電腦模擬選擇最適當的系統參數，以最少的陣元數目來達到合理聚焦。根據模擬結果，本研究建置了由32個陣元所組成的球面換能器，其操作頻率為1 MHz，陣元的直徑為1.0 cm。經由微型水聽器進行聲場量測，用於評估換能器所得的超音波聲場。結果顯示，該系統確實能夠在系統的幾何中心產生焦點。此外，為了使確保腫瘤的燒灼效果，溫度的控制是必需的。本研究提出一套基於模糊理論的溫度控制器，用來控制焦點的溫升曲線，使焦點能在設定的時間內達到指定溫度。

關鍵字

高強度聚焦超音波 ； 幾何聚焦 ； 溫度控制

並列摘要

High-intensity focused ultrasound (HIFU) thermal therapy is a non-invasive means for tumor therapy. The concept is the use of thermal effect of focused ultrasound to produce a local high temperature region at the tumor tissue and resulting in irreversible damage. To ablate a deep-seated tumor, a large scale transducer is needed to compensate the attenuation of ultrasound at the propagation pathway. Owing to the technical limitation, it is difficult to fabricate a large scale, single element HIFU transducer. In this study, a large scale, geometerical ultrasound focusing system via appropriate arrangement of plane transducers on a spherical surface has been developed. Several parameters were investigated, such as the number and the diameter of transducer elements and the distribution of these transducers. Simulation results show that the proposed geometrical focusing system could result in an appropriate focused ultrasound field for HIFU thermal therapy. According to the simulation results, a 25 cm focusing ultrasound transducer with 32 elements, operated at 1 MHz has been developed. Experimental results indicate that, geometrical focusing technique could be an alternative way to substitute for large scale, single element transducer. Furthermore, temperature controller is important during HIFU treatment. A fuzzy controller was proposed to dynamically control temperature elevation. Simulation results suggest that the proposed fuzzy controller is feasible to control the temperature elevation within a prescribed time, even if blood perfusion varies with time.

並列關鍵字

HIFU ； Thermal therapy ； Fuzzy controller

參考文獻

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