許多組織在正常和異常狀態時會顯示出不同的電特性，為了延伸電阻抗系統於組織等級上之應用，需要驗證組織特徵及系統效能之可行性並加以改進，本研究使用電子電路模擬軟體和有限元素分析軟體，首先進行系統電路元件之探討分析，建立關鍵元件特性要求，以達到改進硬體設計，進而提升電阻抗影像系統之功能；其次，透過培養皿之相關結構模擬分析，以確定組織量測之精度要求。對於前者，本研究針對主要之兩種個電流源電路架構模擬分析，提出最適合系統的規格，從模擬與實際量測的結果可知，在系統載波頻率為19.53 kHz時，改良式Howland電路與三運算放大器回授式電路，其輸出阻抗分別可達到 2.82 M 及469 k ，在加入負載電阻從200 至2k 變化時，電流偏量之標準誤差分別為0.017% 及0.194%。從有限元素分析結果，也針對組織培養皿模型建構出三維模型包含電極位置與大小，組織液高度等，其測量誤差在組織液高度為1 cm 而有1% 的誤差和電極位置有0.5 mm時，分別為23.4 mV 及 23.8 mV。另外相較於窄電極，寬電極可提供較均勻的電流分佈及增加訊號雜訊比。整體而言，本研究建立具體之電阻抗影像系統在組織監測應用之可行分析技術基礎。

　Many tissues show the different electrical properties between the normal and malignant states. In order to extend the EIT in tissue level application, it needs to improve the performance of the EIT system and then to investigate its feasibility in measuring the tissue characteristics. In this study, the specifications of circuit components are investigated using circuit simulation and analysis software so as to understand the specification requirement for these components and to improve the EIT system performance. Secondly, the model of culturing dish and tissues are developed and simulated using finite element analysis software so as to assure the measurement precision of the tissue electrical property. For the former study, two types of current source circuit are studied and demonstrated. From the simulation and application results of the system operating in 19.53 kHz, the output impedances for enhanced Howland and 3-Op-amps-feedback types of current source are 2.82 M and 469 k, respectively. The standard deviations of these output current are 0.017% and 0.194%, respectively, as the resistance loads varying from 200  to 2 k. From the results of finite element analysis for 3D tissue culture model including the electrode position, electrode size, medium depth, etc, the measurement precisions are 23.4 mV and 23.8 mV, respectively for the depth of 1 cm with 1% error and electrode position with the deviation of 0.5 mm. As comparing with the narrow electrode, the wide electrode can provide a more uniform current distribution and have the signal-to-noise ratio. Above all, this thesis achieves the sound basis for the feasibility study of the application of EIT in monitoring tissue electrical property.

[1] D. Isaacson “Distinguishability of conductivities by electric current computed tomography,” IEEE Trans. Med. Imaging, vol. MI-5, pp. 92-95, 1986.
[2] J. G. Webster, Electrical Impedance Tomography, Adam, Hilger, 1990.
[3] F. Martini, Fundamentals of Anatomy and Physiology, second edition, N.J.: Upper Saddle River, USA, 1989.
[4] C. W. L. Denyer, Electronics for Real-time and Three-dimensional Electrical Impedance Tomographs, Doctoral dissertation, Oxford Brookes University, 1996.
[5] D. C. Barber and B. H. Brown, “Applied potential tomography,” J. Phys. E., vol. 17, pp. 723–733, 1984.
[6] J. Conway “Electrical impedance tomography for thermal monitoring of hyperthermia treatment: an assessment using in vitro and in vivo measurements,” Clin. Phys. Physiol. Meas., vol. 8, pp. 141-146, 1987.
[7] P. J. Le Pivert, P. Binder, and T. Ougier, “Measurement of intratissue bioelectrical low frequency impedance: A new method to predict per-operatively the destructive effect of cryosurgery,” Cryobiology, vol. 14, pp. 245–250, 1977.
[8] E. Gersing and M. Osypka, “On the frequency range necessary for a multifrequency tomography,” Innov. Tech. Biol. Med., vol. 15, 69-77, 1994.
[9] J. C. Newell, D. G.. Gisser and D. Isaacson, “An electric current tomography,” IEEE Trans. Biomed. Eng., vol. 35, pp. 828-833, 1988.
[10] D. G. Gisser, D Isaacson and J. C. Newell, “Theory and performance of an adaptive current tomography system,” Clin. Phys. Physiol. Meas., 9, Suppl. A, pp. 35-41, 1988.
[11] K. G. Boone and D. S. Holder, “Current approaches to analogue instrumentation design in electrical impedance tomography,” Physiol. Meas., vol. 17, pp. 229-247, 1996.
[12] D. M. Otten and B. Rubinsky, “Cryosurgical monitoring using bioimpedance measurements - a feasibility study for electrical. impedance tomography,” IEEE Trans. Biomed. Eng., vol. 47, pp. 1376–1381, 2000.
[13] R. V. Davalos, D. M. Otten, L. M. Mir and B. Rubinsky, "Electrical impedance tomography for imaging tissue electroporation," IEEE Trans. Biomed. Eng., vol. 51, pp. 761-767, 2004.
[14] C. F. Wu, Electrical Impedance Tomography Design for Tissue Electrical Property Application, Master Thesis, Institute of Biomedical Engineering, National Cheng Kung University, Taiwan, 2004.
[15] W. R. Lionheart, J Kaipio and C. N. McLeod, “Generalized optimal current patterns and electrical safety in EIT,” Physiol. Meas., vol. 22, pp. 85-90, 2001.
[16] J. J. Huang, The Human Body Electrical Impedance Measurement and Analysis System with Temperature Compensation, Doctoral dissertation, Institute of Biomedical Engineering, National Cheng Kung University, Taiwan, 2001.
[17] F. H. Wu, Electrical Impedance Image Reconstruction Using DSP, Master Thesis, Institute of Biomedical Engineering, National Cheng Kung University, Taiwan, 1998.
[18] I. Basarab-Horwath, J. Piotrowski and P. M. McEwan, “Calculated measures of performance in electrical impedance tomography using a finite-element model,” Physiol. Meas., vol. 16, pp. 263-271, 1995.
[19] A. S. Ross, G. J. Saulnier, J. C. Newell and D. Isaacson, “Current source design for electrical impedance tomography,” Physiol. Meas., vol. 24, pp. 509-516, 2003.
[20] G. Cusick, D. S. Holder, A, Birkett and K. G. Boone, “A system for impedance imaging of epilepsy in ambulatory human subjects,” Innov. Tech. Biol. Med., vol.15, pp. 34-39, 1994.
[21] H. X. Wang, C. Wang and W. L. Yin, “Optimum design of the structure of the electrode for a medical for a medical EIT system,” Meas. Sci. Technol., vol. 12, pp. 1020-1023, 2001.
[22] K. S. Cheng, D. Isaacson, J. C. Newell and D. G. Gisser, “Electrode models for electric current computed tomography,” IEEE Trans. Biomed. Eng., vol. 36, pp. 918-923, 1989.
[23] D. J. Nowicki and J. G. Webster, “A one op-amp current source for electrical impedance tomography,” Proc. of Annu. Conference on Engineering in Medicine and Biology, 11 pt 2:457-458, Nov 9, 1989.