Edd Jon F, Horowitz Liana, Rubinsky Boris
Department of Mechanical Engineering, University of California, Berkeley, CA 94720, USA.
IEEE Trans Biomed Eng. 2005 Apr;52(4):695-701. doi: 10.1109/TBME.2005.844042.
The temperature-dependent impedivity of rat liver, transverse abdominal muscle and full skin was determined in vitro as a function of frequency across the temperature range 5 degrees C to 37 degrees C and from 100 Hz to 10 kHz. This study was motivated by an increasing interest in using electrical impedance tomography (EIT) for imaging of cryosurgery and a lack of applicable data in the hypothermic range. Using a controlled-temperature impedance analyzer, it was found that as the temperature is reduced the resulting increase in tissue impedivity is more pronounced at low frequencies and that the beta dispersion, resulting from cell membrane polarization, shifts to lower frequencies. With these new data a simple case study of EIT of liver cryosurgery was examined, using a finite-element model incorporating the Pennes bio-heat equation, to determine the impact of this behavior on imaging accuracy. Overestimation of the ice-front position was found to occur if the EIT system ignored the effects of the low-temperature zone surrounding the frozen tissue. This error decreases with increasing blood perfusion and with higher measurement frequencies.
在5摄氏度至37摄氏度的温度范围内，以及100赫兹至10千赫兹的频率范围内，对大鼠肝脏、腹部横肌和完整皮肤的温度依赖性阻抗率进行了体外测定，该阻抗率是频率的函数。这项研究的动机是人们对使用电阻抗断层成像（EIT）进行冷冻手术成像的兴趣日益浓厚，以及在低温范围内缺乏适用数据。使用控温阻抗分析仪发现，随着温度降低，在低频时组织阻抗率的增加更为明显，并且由细胞膜极化引起的β色散向更低频率移动。利用这些新数据，使用一个包含佩恩斯生物热方程的有限元模型，对肝脏冷冻手术的EIT进行了一个简单的案例研究，以确定这种行为对成像准确性的影响。如果EIT系统忽略冷冻组织周围低温区的影响，会发现冰前沿位置被高估。随着血液灌注增加和测量频率提高，这种误差会减小。
