Estimation of brain tissue response by electrical stimulation in a subject-specific model implemented by conductivity tensor imaging

Nitish Katoch; Youngsung Kim; Bup Kyung Choi; Sang Woo Ha; Tae Hoon Kim; Eun Ju Yoon; Sang Gook Song; Jin Woong Kim; Hyung Joong Kim

doi:10.3389/fnins.2023.1197452

Estimation of brain tissue response by electrical stimulation in a subject-specific model implemented by conductivity tensor imaging

Front Neurosci. 2023 May 23:17:1197452. doi: 10.3389/fnins.2023.1197452. eCollection 2023.

Authors

Nitish Katoch¹, Youngsung Kim², Bup Kyung Choi¹, Sang Woo Ha³, Tae Hoon Kim⁴, Eun Ju Yoon⁵, Sang Gook Song⁵, Jin Woong Kim⁵, Hyung Joong Kim¹

Affiliations

¹ Department of Biomedical Engineering, Kyung Hee University, Seoul, Republic of Korea.
² Office of Strategic R&D Planning (MOTIE), Seoul, Republic of Korea.
³ Department of Neurosurgery, Chosun University Hospital and Chosun University College of Medicine, Gwangju, Republic of Korea.
⁴ Medical Convergence Research Center, Wonkwang University Hospital, Iksan, Republic of Korea.
⁵ Department of Radiology, Chosun University Hospital and Chosun University College of Medicine, Gwangju, Republic of Korea.

Abstract

Electrical stimulation such as transcranial direct current stimulation (tDCS) is widely used to treat neuropsychiatric diseases and neurological disorders. Computational modeling is an important approach to understand the mechanisms underlying tDCS and optimize treatment planning. When applying computational modeling to treatment planning, uncertainties exist due to insufficient conductivity information inside the brain. In this feasibility study, we performed in vivo MR-based conductivity tensor imaging (CTI) experiments on the entire brain to precisely estimate the tissue response to the electrical stimulation. A recent CTI method was applied to obtain low-frequency conductivity tensor images. Subject-specific three-dimensional finite element models (FEMs) of the head were implemented by segmenting anatomical MR images and integrating a conductivity tensor distribution. The electric field and current density of brain tissues following electrical stimulation were calculated using a conductivity tensor-based model and compared to results using an isotropic conductivity model from literature values. The current density by the conductivity tensor was different from the isotropic conductivity model, with an average relative difference |rD| of 52 to 73%, respectively, across two normal volunteers. When applied to two tDCS electrode montages of C3-FP2 and F4-F3, the current density showed a focused distribution with high signal intensity which is consistent with the current flowing from the anode to the cathode electrodes through the white matter. The gray matter tended to carry larger amounts of current densities regardless of directional information. We suggest this CTI-based subject-specific model can provide detailed information on tissue responses for personalized tDCS treatment planning.

Keywords: conductivity tensor; current density; electric field; electrical stimulation; magnetic resonance imaging; transcranial direct current stimulation.