Efficient and robust identification of cortical targets in concurrent TMS-fMRI experiments

Area of Science:

• Neuroscience
• Medical Imaging
• Biophysics

Background:

• Concurrent transcranial magnetic stimulation (TMS) and functional magnetic resonance imaging (fMRI) allow non-invasive investigation of brain networks.
• Accurate localization of TMS targets is crucial for interpreting brain activity, particularly outside motor and visual areas.
• Current methods for TMS target localization are often time-consuming or require specialized equipment.

Purpose of the Study:

• To develop and validate a practical and precise method for identifying TMS coil positions and target cortical locations within an MRI scanner.
• To enable accurate correlation between TMS targets and blood-oxygen-level-dependent (BOLD) activation patterns.
• To facilitate real-time coil placement optimization and post-scan data quality control.

Main Methods:

• A novel marker processing procedure was developed for visualizing TMS coil position and target localization.
• The method was tested on data from 9 scan sessions to quantify precision and reliability.
• Validation was performed using concurrent TMS-fMRI experiments focused on motor network connectivity.

Main Results:

• The marker processing procedure demonstrated minimal variability in coil and target position estimates.
• The developed method accurately and reliably identifies TMS targets in the MR scanner.
• The procedure was successfully validated in TMS-fMRI experiments.

Conclusions:

• The efficient method accurately and reliably identifies TMS targets in the MR scanner, enhancing concurrent TMS-fMRI studies.
• This technique is valuable for optimizing coil placement during scans and for post-scan outlier identification.
• The method is broadly applicable for determining the position and orientation of MR-compatible hardware near the head.