Translational Medical Device Lab, National University of Ireland Galway, Galway, Ireland.
Physiol Meas. 2019 Apr 26;40(4):044005. doi: 10.1088/1361-6579/ab08ba.
A novel method for the imaging of static scenes using electrical impedance tomography (EIT) is reported with implementation and validation using numerical and phantom models. The technique is applicable to regions featuring symmetry in the normal case, asymmetry in the presence of a perturbation, and where there is a known, frequency-dependent change in the electrical conductivity of the materials in the region.
The stroke diagnostic problem is used as a motivating sample application. The head is largely symmetrical across the sagittal plane. A haemorrhagic or ischaemic lesion located away from the sagittal plane will alter this natural symmetry, resulting in a symmetrical imbalance that can be detected using EIT. Specifically, application of EIT stimulation and measurement protocols at two distinct frequencies detects deviations in symmetry if an asymmetrically positioned lesion is present, with subsequent identification and localisation of the perturbation based on known frequency-dependent conductivity changes. Anatomically accurate computational models are used to demonstrate the feasibility of the proposed technique using different types, sizes, and locations of lesions with frequency-dependent (or independent) conductivity. Further, a realistic experimental head phantom is used to validate the technique using frequency-dependent perturbations emulating the key numerical simulations.
Lesion presence, type, and location are detectable using this novel technique. Results are presented in the form of images and corresponding robust quantitative metrics. Better detection is achieved for larger lesions, those further from the sagittal plane, and when measurements have a higher signal-to-noise ratio.
Bi-frequency symmetry difference EIT is an exciting new modality of EIT with the ability to detect deviations in the symmetry of a region that occur due to the presence of a lesion. Notably, this modality does not require a time change in the region and thus may be used in static scenarios such as stroke detection.
报道了一种利用电阻抗断层成像（EIT）对静态场景进行成像的新方法，该方法通过数值和仿体模型进行了实施和验证。该技术适用于在正常情况下具有对称性、在存在扰动时具有非对称性以及在区域中存在已知的、频率相关的电导率变化的区域。
以中风诊断问题为例，作为一个有启发性的应用示例。头部在矢状面两侧基本对称。如果病变位置偏离矢状面，将会改变这种自然的对称性，从而导致可以通过 EIT 检测到的对称失衡。具体来说，如果存在位置不对称的病变，应用 EIT 刺激和测量方案在两个不同的频率下，可以检测到对称性的偏差，随后根据已知的频率相关电导率变化来识别和定位病变。使用解剖学上精确的计算模型，展示了使用具有频率相关（或独立）电导率的不同类型、大小和位置的病变来实现该技术的可行性。此外，还使用具有频率相关的扰动的现实实验头仿体来验证该技术，这些扰动模拟了关键的数值模拟。
使用这种新的技术可以检测到病变的存在、类型和位置。结果以图像和相应的稳健定量指标的形式呈现。对于较大的病变、距离矢状面更远的病变以及具有更高信噪比的测量，检测效果更好。
双频对称差异 EIT 是一种令人兴奋的 EIT 新模态，具有检测由于病变存在而导致的区域对称性偏差的能力。值得注意的是，该模态不需要区域时间变化，因此可用于中风检测等静态场景。
