Witkowska-Wrobel Anna, Aristovich Kirill, Crawford Abbe, Perkins Justin D, Holder David
Medical Physics and Biomedical Engineering, University College London, UK.
Medical Physics and Biomedical Engineering, University College London, UK.
Neuroimage. 2021 Jul 1;234:117972. doi: 10.1016/j.neuroimage.2021.117972. Epub 2021 Mar 20.
Intracranial EEG is the current gold standard technique for localizing seizures for surgery, but it can be insensitive to tangential dipole or distant sources. Electrical Impedance Tomography (EIT) offers a novel method to improve coverage and seizure onset localization. The feasibility of EIT has been previously assessed in a computer simulation, which revealed an improved accuracy of seizure detection with EIT compared to intracranial EEG. In this study, slow impedance changes, evoked by cell swelling occurring over seconds, were reconstructed in real time by frequency division multiplexing EIT using depth and subdural electrodes in a swine model of epilepsy. EIT allowed to generate repetitive images of ictal events at similar time course to fMRI but without its significant limitations. EIT was recorded with a system consisting of 32 parallel current sources and 64 voltage recorders. Seizures triggered with intracranial injection of benzylpenicillin (BPN) in five pigs caused a repetitive peak impedance increase of 3.4 ± 1.5 mV and 9.5 ± 3% (N =205 seizures); the impedance signal change was seen already after a single, first seizure. EIT enabled reconstruction of the seizure onset 9 ± 1.5 mm from the BPN cannula and 7.5 ± 1.1 mm from the closest SEEG contact (p<0.05, n =37 focal seizures in three pigs) and it could address problems with sampling error in intracranial EEG. The amplitude of the impedance change correlated with the spread of the seizure on the SEEG (p <<0.001, n =37). The results presented here suggest that combining a parallel EIT system with intracranial EEG monitoring has a potential to improve the diagnostic yield in epileptic patients and become a vital tool in improving our understanding of epilepsy.
颅内脑电图是目前用于手术中癫痫灶定位的金标准技术，但它可能对切线偶极子或远处的癫痫源不敏感。电阻抗断层成像（EIT）提供了一种新方法来提高覆盖范围和癫痫发作起始部位的定位。EIT的可行性此前已在计算机模拟中进行了评估，结果显示与颅内脑电图相比，EIT检测癫痫的准确性有所提高。在本研究中，通过在癫痫猪模型中使用深部和硬膜下电极的频分复用EIT实时重建了数秒内细胞肿胀引起的缓慢阻抗变化。EIT能够在与功能磁共振成像（fMRI）相似的时间进程中生成癫痫发作事件的重复图像，但没有其显著局限性。使用由32个并行电流源和64个电压记录器组成的系统记录EIT。在5头猪中通过颅内注射苄青霉素（BPN）引发癫痫发作，导致重复的峰值阻抗增加3.4±1.5 mV和9.5±3%（N = 205次癫痫发作）；在单次首次癫痫发作后即可观察到阻抗信号变化。EIT能够在距BPN插管9±1.5 mm和距最近的立体定向脑电图（SEEG）接触点7.5±1.1 mm处重建癫痫发作起始部位（p<0.05，3头猪中有37次局灶性癫痫发作），并且它可以解决颅内脑电图中的采样误差问题。阻抗变化的幅度与癫痫发作在SEEG上的扩散相关（p <<0.001，n = 37）。此处呈现的结果表明，将并行EIT系统与颅内脑电图监测相结合有潜力提高癫痫患者的诊断率，并成为增进我们对癫痫理解的重要工具。
