中文摘要

組織的病變、退化或改變通常與其黏彈性的變化有關，目前組織材質特性的量測大多為離體實驗與侵入性的方法，其精確度及信賴度通常被質疑。超音波為非侵入性、無傷害且安全性無顧慮的科技，由於電子訊號處理科技的快速進步及醫療成本的考量，利用超音波來評估量化軟組織的特性，是近年來最熱門且具潛力的方法。有關都卜勒超音波研發皆使用射頻功率放大器，其價格昂貴，提供之電壓有限，僅使用到射頻功率放大器的一小部份頻率範圍，而且消耗功率更是遠小於射頻電路系統，因此本研究之目的為發展一套可應用於量測組織聲學特性及黏彈係數的脈波超音波系統之激發放大器。
本研究之設計包含操作界面、前級激發訊號產生、訊號放大、隔離限制器等模組。操作界面：系統初期設計以操作界面來模擬GPIB所輸出控制訊號，主要控制參數包含訊號頻率、脈波重複頻率、脈波數目。前級激發訊號產生：將操作界面輸出之控制訊號產生激發超音波探頭之前級控制。訊號放大（功率放大器）：將訊號放大至設定電壓，並輸出足夠功率以驅動超音波探頭。隔離限制：在脈波式都卜勒超音波系統中，每顆探頭同時作為發射及接收端，為防此激發訊號與回波訊號進入後級放大器中，故需要此模組來隔離發射和回波訊號。
目前己完成各模組功能、整合、測試；操作界面已完成處理鍵盤輸入、LCDM顯示、PRF訊號產生、系統設定值輸出及系統與探頭間開關之控制。前級激發控制訊號可依輸入設定（訊號頻率、脈波數目及PRF）產生激發控制訊號。訊號放大驅動為本系統設計中最為挑戰的部份，電源供應器或高頻高壓放大電路，皆經過數次不同之設計製作而成，目前己能產生3.5、5、7.5 MHZ三組頻率且振幅可達270 VP－P之輸出訊號，但輸出訊號前後段有波形失真之情況，因關鍵元件尚未取得，期能早日改進解決。隔離限制器模組採用二極體電路設計，可將激發訊號與探頭回波訊號確實隔離，達成系統設計的目的。
系統目前己針對輸出訊號之準確度及訊號雜訊比完成初步測試，結果顯示輸出訊號之中心頻率誤差範圍在0.1MHz內，電壓振幅可達275V。在訊號雜訊比方面，雖初步測試結果SNR值不盡理想，但此為電路雛型初期設計，未來可透過電路改善或其他設計架構等不同方式來改善。
本研發系統部份尚待加強改進，但未來可朝下列幾個方向擴充與發展：（1）將前級激發訊號產生模組電路設計改良為可調頻式輸出，以增加輸出訊號範圍，（2）實際應用於脈波式都卜勒超音波量測黏彈特性系統中並量測、分析本系統之效能，（3）將系統擴大，增加儀器放大器，建立整套杜卜勒超音波系統，（4）將本研發系統應用實現於其他連續式超音波系統。

Abstract
The viscoelastic properties are critical to specific function for each living organ and fundamental in biomechanical modeling of tissue behavior. Currently invasive methods are often used to measure biomechanical properties in vitro, which are deviated from those in living status and difficult to be applied in practice. During the last decade, sonoelasticity has being studied by the Doppler ultrasonic technology with low frequency tissue vibration. It seems to be prospective in developing non-invasive, in vivo measuring technology for viscoelasticity. The RF power amplifier, which is high frequency, power output and cost, is improperly applied to excite the ultrasonic transducers (UTS) with frequency at MHz order. The purpose of this research is to design a power transmitter system specified for a pulsed Doppler ultrasonic measuring system.
The system design consists of interface control (IC), burst signal generator (BSG), power amplifier (PA) and isolated limiter (IL) modules. The IC unit is developed for signal frequency, pulse repetitive frequency and number setting. The BSG is to generate pre-stage excited signal for the UTS, according to the setup from IC unit. Then the PA is designed for output voltage and power amplification to directly excite the UTS. The IL circuit design is used diodes to isolate the input transmitting signal to and the reflective signal from the UTS.
The prototyped power transmitter system has been developed completely with system component calibration. The IC unit has provided functions with keyboard input, LCDM display, PRF signal generation and output relay control. The PA provides maximally output signal of 270VP-P with 3.5, 5 and 7.5 MHz to excite the UTS. The calibration results show that there is signal distortion appearing in the forward and backward parts of each PRF signal. An improved method is to look into better IC component. The calibration of whole system indicates that the output standard error of central frequencies of 3.5, 5 and 7.5 MHz is within 0.1 MHz range. The results also show that maximal SNR (signal to noise ratio) is 53dB with minimal at 26dB. The system SNR is expected to be improved by circuit design.
The future system research and development are recommended as following: (1) improved BSG design to provide adjustable frequency setting; (2) to implement the system in the pulsed Doppler ultrasonic measuring system (replace the conventional RF power amplifier) to non-invasive, in vivo measuring for soft tissue’ viscoelasticity; and (3) to expand system design and development for the application of conventional ultrasonic instrumentation.

【1】 Yoshiki Yamakoshi, Junichi Sato, and Takuso Sato, “ Ultrasounic Imaging of Internal Vibration of Soft Tissue under Forced Vibration ,” IEEE Trans. on ultrasonic, ferroelectrics, and frequency control society, Vol. 37, No. 2, pp.45-53, MARCH, 1990.
【2】 T. A. Krouskop, D. R. Dougherty, F. S. Winson, “ A pulsed Doppler ultrasonic system for making noninvasive measurements of the mechanical properties of soft tissue,” J. Rehabilitation Research and Development Vol. 24, No. 2, pp.1-8, Spring, 1987.
【3】 Halliday et al., “Fundamentals of Physics 4th Edition” John Wiley & Sons, Inc.
【4】 Krautkramer, “Ultrasonic Testing of Materials” Springer-Verlag Berlin Heidelberg New York 1969.
【5】 Douglas A. Christensen, “Ultrasonic Bioinstrumentation”, 1988.
【6】 K. Kirk Shung, “Principles of Medical Imaging”, Academic Press, Inc. 1992..
【7】 K Kirk Shung, Gary A. Thieme Edited, “Ultrasound Scattering in Biological Tissues”,CRC Press, Inc, 1993.
【8】 Sophocles J. Orfanidis, “Introduction to signal processing”, Prentice Hall International Editions, 1996.
【9】 Ping He, “Acoustic Attenuation Estimation for Soft Tissue from Ultrasound Echo Envelope Peaks”, IEEE Trans. Ultrasonics, Ferroelectrics, and frequency Control.” Vol. 36, No. 2, MARCH 1989.
【10】 黃鐵強,“臨片杜卜勒心臟超音波學光譜與彩色血流影像”, 合記圖書出版社,pp.4-12,1991.
【11】 DONLAND W.BAKER,“Pulse Ultrasonic Doppler Blood-Flow Sensing”, IEEE Trans. On sonics & ultrasonic, Vol. Su-17, No. 3, JULY 1970.
【12】 Chuen-Ru Hou,” Design and Development of A Pulsed Wave Doppler Ultrasonic System for Measuring the Viscoelasticity of Soft Tissue”, National Cheng Kung University, 2002
【13】 Lewis F.Brown, ”Design Considerations fo Piezoelectric Polymer Ultrasound Transducers”, IEEE Transactions on Ultrasonics, Ferroelectrics, and frequency control, vol. 47,no 6, November 2000.
【14】 David H.Evans,W.Norman McDicken, “Doppler Ultrasound Physics ,Instrumentation and Signal Processing” ,John Wiley & Sons Ltd,1989,2000.
【15】 . Y. C. Fung, “Biomechanics mechanical properties of living tissue,” New York；Springer-Verlag, 1981.
【16】 H.L. Oestreicher, “Field and Impedance of an Oscillating Sphere in a Viscoelastic Medium With an Application to Biophysics”, J. Acoustic Soc. Am, vol. 23,pp. 707-714,1951.
【17】 R.J. Dickinson and C.R. Hill ,”Measurement of Soft Tissue Using Correlation Between A-Scan”, Ultrasound Med. Biol. ,vol. 8,pp263-277, 1982.
【18】 J.C. Birnholz and E.E Farrell, ”Fetal Lung Development: Compressibility As a Measure of Maturity”, Radiology, vol. 157,pp. 495-498,1985.
【19】 Y. Yamakoshi and T. Sato, “Ultrasonic Imaging of Internal Vibration of soft Tissue Under Forced Vibration”, IEEE Trans. Ultrason. Ferroel. Freq. Control, vol.17,pp.45-53.
【20】 R.M. lerner and K.J. Parker, “Sono-elasticity in Ultrasonic Tissue Characterization and Echographic Imaging”, In Proc. 7th Eur. Comm. Workshop, J.M. thijssen , ed., October 1987,Nijmegen,The Netherlands.
【21】 T.A. Krouskop, D.R. Dougherty and S.F. Levinson, ”A Pulsed Doppler Ultrasonic System for Making Nonivasive Measurements of the Mechanical Properties of Soft Tissue”, J. Rehabil. Res. Dev., vol. 24, pp1-8,1987.
【22】 S.F Levinson, Masahiko shinagawa and T. Sato, ”Sonoelastic Determination of human Skeletal Muscle Elasticty”, J. Biomechnics, vol.28, pp.1145-1154,1995
【23】 Adel S. Sedra,Kenneth C. Smith, 曹恆偉,林浩雄合譯,“微電子電路（下）”,台北圖書有限公司,1992.
【24】 黃明煌,“類比積體電路應用”,全華科技圖書有限公司,1987
【25】 徐天佑,“電子裝置與電路理論（下）”,超級科技圖書股份有限公司,1989
【26】 陳連春,“電源電路設計要領”,建興出版社, 1995
【27】 簡章華,“轉換式電源供給器”,全華科技圖書公司, 1985
【28】 鄭振東,“轉換式電源穩定器設計要訣“,建興出版社, 1997
【29】 鈴木雅臣,陳連春譯,“FET/電功率MOS切換電路”,建興出版社,1999.
【30】 鈴木雅臣,陳連春譯,“電晶體電路設計應用鐵則”,建興出版社,1998.
【31】 林容益,“CPLD數位電路設計發展應用”,全華科技圖書股份有限公司, 1999.
【32】 謝沐田,“高低頻變壓器設計”,全華出版社,1999.
【33】 Reuben Lee, Leo Wilson, Charles E.Carter著,黃文良、趙世文、王志浩譯,“電子變壓器及電路”,全華出版社,1997.
【34】 吳一農,"單晶片8051實務",松崗出版社,1999.
【35】 上靖光電 文字型LCD 16*2 Data Sheet,1998年.
【36】 袁帝文,王岳華,“高頻電路設計”,高立圖書有限公司,民國86年
【37】 張煜,“電子儀表與測量“,東華書局,民國79年.
【38】 蘇奕肇，“音頻用儀器與量測技術”，全華科技圖書股份有限公司，民國88年