大鼠死后肌肉组织电阻抗幅值和相位角变化推断死后间隔时间的研究

目的研究大鼠死后皮下肌肉组织电阻抗幅值和相位角的变化规律，探讨生物电阻抗技术推断中晚期PMI的价值。方法利用四电极阻抗测量系统测量20只大鼠死后4种不同环境温度皮下肌肉组织电阻抗幅值和相位角，并用Excel及MATLAB对所得的离散阻抗数据进行处理。结果（1）所有死亡大鼠皮下肌肉组织的电阻抗幅值都呈现出相似的先升后降的变化趋势，且中、长期的下降部分有一定的线性变化趋势。电阻抗下降段斜率与温度的变化呈正相关关系，且在不同环境温度时，下降段斜率与PMI的相关性都较高，均大于0．97。因此，有可能利用这一线性关系推断中、晚期PMI。（2）所有死亡大鼠皮下肌肉组织的电阻抗相位角没有相似的变化规律，其变化杂乱无章。结论如果找出电阻抗幅值下降段起点、峰值、斜率这3者之间的确定关系，就可利用下降段的线性关系为推断中晚期PMI提供一定的判断依据。

Estimation of the postmortem interval by the magnitude and phase angle changes of musculature impedance in rat cadavers

Objective To investigate the role of the magnitude and phase angle changes of musculature impedance in rat cadavers,in order to evaluate the significance of middle and late PMI estimation by Bio-impedance measurement.Methods The magnitude and phase angle changes of musculature impedance in 20 rat cadavers at different temperature were measured by applying a four-electrode Bio-impedance measurement system.The discrete data was analyzed by Excel and MATLAB methods.Results(1) All endermic musculature impedance magnitude of rat cadavers presented the similar change,upgrading first,downgrading later,and the middle or late phase of downgrading showing some linear tendency.Meanwhile,the slope rate of the downgraded impedance was positively related with changes of temperature.The correlation of the slope rate for downgrade part from each group at different temperature to PMI was quite high,all over 0.97,which could be used to estimate PMI at middle or late stage.(2) All phase angle of endermic musculature impedance showed no regular change,the changes of which were in a great mess.Conclusion The linear relation of the downgraded part drawn from the definite correlation of beginning point,peak value and slope rate could be used to provide the evidence for estimating the middle and late stage of PMI.