A high-resolution computational localization method for transcranial magnetic stimulation mapping

Shinta Aonuma; Jose Gomez-Tames; Ilkka Laakso; Akimasa Hirata; Tomokazu Takakura; Manabu Tamura; Yoshihiro Muragaki

doi:10.1016/j.neuroimage.2018.01.039

A high-resolution computational localization method for transcranial magnetic stimulation mapping

Neuroimage. 2018 May 15:172:85-93. doi: 10.1016/j.neuroimage.2018.01.039. Epub 2018 Jan 28.

Authors

Shinta Aonuma¹, Jose Gomez-Tames¹, Ilkka Laakso², Akimasa Hirata³, Tomokazu Takakura⁴, Manabu Tamura⁵, Yoshihiro Muragaki⁵

Affiliations

¹ Nagoya Institute of Technology, Department of Electrical and Mechanical Engineering, Nagoya, Aichi, 466-8555, Japan.
² Aalto University, Department of Electrical Engineering and Automation, Espoo, FI-00076, Finland.
³ Nagoya Institute of Technology, Department of Electrical and Mechanical Engineering, Nagoya, Aichi, 466-8555, Japan. Electronic address: ahirata@nitech.ac.jp.
⁴ Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, 162-8666, Japan.
⁵ Faculty of Advanced Techno-Surgery, Institute of Advanced Biomedical Engineering and Science, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, 162-8666, Japan; Department of Neurosurgery, Neurological Institute, Tokyo Women's Medical University, Shinjuku-ku, Tokyo, 162-8666, Japan.

PMID: 29360575
DOI: 10.1016/j.neuroimage.2018.01.039

Abstract

Background: Transcranial magnetic stimulation (TMS) is used for the mapping of brain motor functions. The complexity of the brain deters determining the exact localization of the stimulation site using simplified methods (e.g., the region below the center of the TMS coil) or conventional computational approaches.

Objective: This study aimed to present a high-precision localization method for a specific motor area by synthesizing computed non-uniform current distributions in the brain for multiple sessions of TMS.

Methods: Peritumoral mapping by TMS was conducted on patients who had intra-axial brain neoplasms located within or close to the motor speech area. The electric field induced by TMS was computed using realistic head models constructed from magnetic resonance images of patients. A post-processing method was implemented to determine a TMS hotspot by combining the computed electric fields for the coil orientations and positions that delivered high motor-evoked potentials during peritumoral mapping. The method was compared to the stimulation site localized via intraoperative direct brain stimulation and navigated TMS.

Results: Four main results were obtained: 1) the dependence of the computed hotspot area on the number of peritumoral measurements was evaluated; 2) the estimated localization of the hand motor area in eight non-affected hemispheres was in good agreement with the position of a so-called "hand-knob"; 3) the estimated hotspot areas were not sensitive to variations in tissue conductivity; and 4) the hand motor areas estimated by this proposal and direct electric stimulation (DES) were in good agreement in the ipsilateral hemisphere of four glioma patients.

Conclusion(s): The TMS localization method was validated by well-known positions of the "hand-knob" in brains for the non-affected hemisphere, and by a hotspot localized via DES during awake craniotomy for the tumor-containing hemisphere.

Keywords: Brain mapping; Brain tumor; Direct electrical stimulation; Hotspot; Transcranial magnetic stimulation; Volume conductor model.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Brain / diagnostic imaging*
Brain Mapping / methods*
Evoked Potentials, Motor / physiology
Female
Humans
Image Interpretation, Computer-Assisted / methods*
Magnetic Resonance Imaging / methods
Male
Middle Aged
Transcranial Magnetic Stimulation / methods*