Modeling electrical impedance in brain tissue with diffusion tensor imaging for functional neurosurgery applications.

Area of Science:

• Neuroscience and Biomedical Engineering
• Medical Imaging and Computational Modeling

Background:

• Electrical impedance measurements were historically used for intraoperative brain tissue differentiation but were superseded by advanced imaging.
• Current limitations include a lack of established tissue-impedance relationships and verified parameters for human brain impedance modeling.

Purpose of the Study:

• To address the need for experimentally verified parameters for non-invasive, high-resolution intracerebral impedance prediction using advanced imaging and modeling.
• To refine finite element method (FEM) model parameters by comparing predictions with intraoperative impedance measurements in human brains.

Main Methods:

• Utilized FEM to simulate single- and dual-electrode impedance measurements through canonical and patient-specific diffusion tensor imaging (DTI)-based brain models.
• Compared simulated impedance predictions with 308 intraoperative single-electrode impedance measurements from five deep brain stimulation (DBS) patients.
• Calibrated model coefficients using experimental data to refine human brain impedance modeling parameters.

Main Results:

• DTI-FEM models showed similar performance for single- and dual-electrode configurations.
• Single-electrode impedance measurements demonstrated significant spatial variation even in white matter, influenced by factors like white matter density.
• Calibrated model predictions reliably estimated intraoperative measurements (R=0.784±0.116), and an updated slope coefficient (k=0.0649) for the DTI conductance model was derived for human brains.

Conclusions:

• This study presents the first comparison of impedance estimates from imaging-based models with in vivo experimental measurements in human brain tissue.
• Accurate, non-invasive, imaging-based impedance prediction holds significant potential for functional neurosurgery, including tissue mapping and intraoperative electrode localization for DBS.