Dowrick T, Blochet C, Holder D
Department of Medical Physics & Biomedical Engineering, University College London, London, UK.
Physiol Meas. 2016 Jun;37(6):765-84. doi: 10.1088/0967-3334/37/6/765. Epub 2016 May 20.
Electrical impedance tomography (EIT) could be used as a portable non-invasive means to image the development of ischaemic stroke or haemorrhage. The purpose of this study was to examine if this was possible using time difference imaging, in the anesthetised rat using 40 spring-loaded scalp electrodes with applied constant currents of 50-150 μA at 2 kHz. Impedance changes in the largest 10% of electrode combinations were -12.8% ± 12.0% over the first 10 min for haemorrhage and +46.1% ± 37.2% over one hour for ischaemic stroke (mean ± SD, n = 7 in each group). The volume of the pathologies, assessed by tissue section and histology post-mortem, was 12.6 μl ± 17.6 μl and 12.6 μl ± 17.6 μl for haemorrhage and ischaemia respectively. In time difference EIT images, there was a correspondence with the pathology in 3/7 cases of haemorrhage and none of the ischaemic strokes. Although the net impedance changes were physiologically reasonable and consistent with expectations from the literature, it was disappointing that it was not possible to obtain reliable EIT images. The reason for this are not clear, but probably include confounding effects of secondary ischaemia for haemorrhage and tissue and cerebrospinal fluid shifts for the stroke model. With this method, it does not appear that EIT with scalp electrodes is yet ready for clinical use.
电阻抗断层成像（EIT）可作为一种便携式非侵入性手段，用于对缺血性中风或出血的发展情况进行成像。本研究的目的是探讨在麻醉大鼠中使用40个弹簧加载头皮电极，以2kHz的频率施加50 - 150μA的恒定电流，通过时间差成像是否可行。对于出血，在最初10分钟内，最大的10%电极组合的阻抗变化为-12.8%±12.0%；对于缺血性中风，在一小时内为+46.1%±37.2%（每组n = 7，均值±标准差）。通过死后组织切片和组织学评估的病变体积，出血和缺血分别为12.6μl±17.6μl和12.6μl±17.6μl。在时间差EIT图像中，出血的7例中有3例与病变相符，而缺血性中风无一例相符。尽管净阻抗变化在生理上是合理的，且与文献预期一致，但无法获得可靠的EIT图像令人失望。其原因尚不清楚，但可能包括出血继发缺血的混杂效应以及中风模型中组织和脑脊液移位的影响。用这种方法，头皮电极的EIT似乎尚未准备好用于临床。
