電阻抗斷層掃描系統－新式醫學成像技術

Electrical Impedance Tomograph-A New Medical Imaging Technique

鄭國順(Kuo-Sheng Cheng) ； 盧宜裕(Yi-Yu Lu) ； 陳政宇(Cheng-Yu Chen)

《科儀新知》 151期 (2006/04) Pp. 68-75

https://doi.org/10.29662/IT.200604.0008

摘要

電阻抗斷層掃描系統是透過體表電極組，應用外加電流與測量電壓方式，經由重建演算法而建構出橫截面電阻係數（電導係數）或介電係數之影像成像系統，可以提供內部電氣特性之影像。本系統之硬體設計包括(1)數位振盪電路，(2)電流產生電路，(3)數位控制電路，(4)電壓量測電路和(5)電極組。採用電路模組化、多電流通道與多頻率為設計理念加以實現，便於往後測試與檢修；具有多頻率15kHz、30kHz、80kHz以及10kHz與80kHz頻率混合的等正弦波載波訊號之設計。整體系統之完成規格為32電極數，最大電流可以設定範圍為±5mA(rms)，類比／數位轉換解析度是12位元，取樣頻率為312kHz，可量測電壓範圍為±4V(rms)，最大負載阻抗是800W，所需要供應電源為±12V、5V。最後使用單步牛頓－拉夫遜法影像重建演算法重建假體影像，證明系統可行性。

並列摘要

Electrical impedance tomograph is a system that produces the electrical impedance image of the cross section of the body based on the application of current and measurement of voltage from the periphery. The impedance may be represented as two parameters such as resistivity (conductivity) and permittivity. It provides the electrical property of the tissue inside the body. The hardware design of this system includes (1) oscillator circuit, (2) current generator, (3) digital control circuit, (4) voltage measurement circuit, and (5) electrode array. The design is based on the modularized circuit, multi-current channels, and multi-frequency concept for better system testing and maintenance. The frequency for the carrier signal of proposed system may be set to be 15 kHz, 30 kHz, 80 kHz, and the combined 10 kHz and 80 kHz. The specifications of the whole system may be summarized as that it has 32 electrodes, the maximal current is ±5 mA (rms), each current generators has 12-bit resolution in current setting, the sampling rate is 312 kHz, the input voltage range is ±4 V (rms), and the maximal load resistance is 800 W. The needed voltage supplies are ±12 V and 5 V. Finally, it is demonstrated to produce resistivity image for the phantom using one-step Newton-Raphson based image reconstruction algorithm.