生物電阻抗是一種電阻抗測量技術，極具臨床應用潛力，也可以發展成為身體內部組織電特性成像。由於組織電特性會隨著頻率有所變化，不同頻率之電阻抗變化可以提供不同資訊，因此多頻率的生物電阻抗測量有其重要性。為了滿足多元化臨床應用，故本研究主要是研發出一套具有擴充性的多頻率生物電阻抗測量系統，其三個主要的部份，一為硬體設計，二為軟體設計，三則為系統效能驗證。在硬體架構的設計包含三個部份，(1)系統主要裝置，(2)延伸式通道切換裝置，與 (3)電極設計。軟體功能上主要分為三個主要部份，(1)阻抗測量參數設定，(2)系統校正，與(3)數據擷取。本論文所研發系統的特性綜合如下，系統的總諧波失真 (THD) 約為0.5%，而增益因子 (gain factor)的變異係數則低於0.1%以下。阻抗測量實驗結果，與Agilent 4263B 阻抗測量儀比較，在測量精密電阻方面，其最大差異誤差低於2%；在三元件模型測量方面，其最大差異低於1.5%；在電極裝置誤差測試方面，其最大誤差也低於3%。在組織的多頻率測量上，本系統比阻抗測量儀提供更多的頻率測量點。綜合上述，本系統具有實際臨床應用的能力，同時在測量組織的電特性也能提供阻抗頻譜資訊；系統具有下列特點，(1)多頻率測量，(2)可擴充性架構，(3)開發成本低，(4)具可攜性，與(5)電腦圖形控制介面。

Bioimpedance technology is a kind of impedance measurement technology, and has great potential in clinical applications. It can also be developed for imaging the electrical property inside the body. Due to the property of tissues, the impedance may vary with the frequency of measuring signal. Thus, the multi-frequency impedance measurement plays an important role in characterizing the electrical property of tissues. For multiple clinical applications, the multi-frequency bioimpedance measuring system with extensibility is developed in this thesis. There are three main parts in this study, which are (1) hardware design, (2) software design, and (3) system performance evaluation and testing. The hardware design includes (1) main device for impedance measurement, (2) external device switch, and (3) electrode design. The software program includes (1) measurement parameter settings, (2) system calibrations, and (3) data acquisition. The performances for the developed system are summarized as follows. The total harmonic distortion (THD) is below 0.5%. The coefficient of variation about gain factor error is smaller than 0.1%. The experimental results of bioimpedances are also compared with the Agilent 4263B LCR meter. For the standard resistor measurement, the maximal percentage difference between the proposed system and LCR meter is within 2%. For a three-element model measurement, the maximal percentage of difference is below 1.5%. The maximal error of electrode re-placement is lower than 3%. Above all, this developed system can provide more points of measuring frequency in comparison with the LCR meter in bioimpedance spectroscopy. From the experimental results, it is demonstrated that the proposed system may be used for a variety of clinical applications. In summary, the proposed system has the following advantages: (1) the multi-frequency measurement capability, (2) the extensible system architecture, (3) low development cost, (4) good portability, and (5) control software with friendly GUI.

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