Use of anisotropic modelling in electrical impedance tomography; Description of method and preliminary assessment of utility in imaging brain function in the adult human head
Use of anisotropic modelling in electrical impedance tomography; Description of method and preliminary assessment of utility in imaging brain function in the adult human head
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DOI：
10.1016/j.neuroimage.2008.07.023
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发表时间：
2008-11-01
期刊：
影响因子：
5.7
通讯作者：
Holder, David S.
中科院分区：
文献类型：
--
作者：
Abascal, Juan-Felipe P. J.;Arridge, Simon R.;Holder, David S.
电阻抗断层扫描（EIT）是一种成像方法，其使得能够从多个阻抗测量产生对象的体积电导率图。它有可能成为一种便携式非侵入性成像技术，特别是在成像脑功能。精确的数值正演模型可用于改善图像重建，但到目前为止，采用了各向同性组织电导率的假设。这可能会引入不准确性，因为身体组织，特别是头部成像中的白色物质和颅骨等身体组织是高度各向异性的。本研究的目的是，第一次，开发一种方法，将各向异性的正向数值模型EIT的头部和评估的情况下，线性重建的一个例子的人的头部的图像质量的改善。从结构MRI中产生具有头皮、颅骨、CSF和脑段的成人头部的真实有限元模型（FEM）。根据同一受试者的扩散张量MRI估计大脑的各向异性，并根据结构信息估计头骨的各向异性。提出了一种在正演模型中考虑各向异性的方法及其在图像重建中的应用。通过产生前向数据，然后使用灵敏度矩阵方法进行线性重建，在计算机模拟中评估重建图像质量的改善。参考电导率的各向异性和各向同性正演模型之间的平均边界数据差异为50%。在图像重建中使用正确的各向异性FEM，而不是各向同性FEM，纠正了24 mm的误差，在成像中，位于海马体的10%的电导率降低，改善了大脑深处的电导率变化的定位，并由于癫痫4-17 mm，总体上，导致图像质量的大幅改善。这表明在用于图像重建的数值模型中并入各向异性可能改善EIT图像质量。(c)2008年爱思唯尔公司All rights reserved.
Electrical Impedance Tomography (EIT) is an imaging method which enables a volume conductivity map of a subject to be produced from multiple impedance measurements. It has the potential to become a Portable non-invasive imaging technique of particular use in imaging brain function. Accurate numerical forward models may be used to improve image reconstruction but, until now, have employed an assumption of isotropic tissue conductivity. This may be expected to introduce inaccuracy, as body tissues, especially those such as white matter and the skull in head imaging, are highly anisotropic. The purpose of this study was, for the first time, to develop a method for incorporating anisotropy in a forward numerical model for EIT of the head and assess the resulting improvement in image quality in the case of linear reconstruction of one example of the human head. A realistic Finite Element Model (FEM) of an adult human head with segments for the scalp, skull, CSF, and brain was produced from a structural MRI. Anisotropy of the brain was estimated from a diffusion tensor-MRI of the same subject and anisotropy of the skull was approximated from the structural information. A method for incorporation of anisotropy in the forward model and its use in image reconstruction was produced. The improvement in reconstructed image quality was assessed in computer simulation by producing forward data, and then linear reconstruction using a sensitivity Matrix approach. The mean boundary data difference between anisotropic and isotropic forward models for a reference conductivity was 50%. Use of the correct anisotropic FEM in image reconstruction, as opposed to an isotropic one, corrected an error of 24 mm in imaging a 10% conductivity decrease located in the hippocampus, improved localisation for conductivity changes deep in the brain and due to epilepsy by 4-17 mm, and, overall, led to a substantial improvement on image quality. This suggests that incorporation of anisotropy in numerical models used for image reconstruction is likely to improve EIT image quality. (c) 2008 Elsevier Inc. All rights reserved.