A low-cost system for coil tracking during transcranial magnetic stimulation

Abstract

Purpose Accurate coil placement over a target area is critical during transcranial magnetic stimulation (TMS), as small deviations can alter testing outcomes. Accordingly, frameless stereotaxic systems (FSS) are recommended for reliable coil placement during TMS applications. However, FSS is not practical due to the cost associated with procuring such systems. Therefore, the purpose of this study was to develop a low-cost TMS coil tracking approach using simple webcams and an image processing algorithm in LabVIEW Vision Assistant. Methods A system was created using two webcams, retroreflective markers, and computer stereovision, for tracking the TMS coil over a target area. Accuracy of the system was validated in both the global and local reference frames, while repeatability was measured within- and between-days for placement of the TMS coil over the target area relative to the head. The feasibility of our system was also verified by collecting motor evoked potentials (MEPs) of first dorsal interosseous muscle from human subjects. Results The results of this study indicated that the system was highly accurate and repeatable, and could track the coil position with < 5mm error and orientation < 1.1° error from the target. We also observed larger and more consistent MEPs when stimulating the brain using feedback from the coil tracking system than when the examiner attempted to stimulate without any feedback. Conclusion The findings suggest that webcam-based coil tracking is a feasible low-cost solution to track coil positions during TMS procedures.

The Effects of Stimulator, Waveform, and Current Direction on Intracortical Inhibition and Facilitation: A TMS Comparison Study

“…Furthermore, a rather small sample size may have restrained us from detecting effects with low effect sizes. Lastly, we did not use a coil tracking system, which may improve coil positioning (Washabaugh and Krishnan, 2016). Although, for motor-cortex centered SICI assessments hand-held and navigated approaches have shown to result in comparable reliability (Fleming et al, 2012).…”

Stimulation Parameters Used During Repetitive Transcranial Magnetic Stimulation for Motor Recovery and Corticospinal Excitability Modulation in SCI: A Scoping Review

“…This may be due to the high cost of the currently available systems. Some easy-to-use and costless alternatives have been proposed and seem to provide reliable results (Cincotta et al, 2010;WashaBaugh and Krishnan, 2016;Rodseth et al, 2017;Ambrosini et al, 2018). These systems can help the systematic reporting of hotspot coordinates and monitor coil shifts across the session (Corp et al, 2020;Corp et al, 2021).…”

Devices and Technology in Transcranial Magnetic Stimulation: A Systematic Review

“…In order to provide more precise positioning of the coil, camera-based infrared (IR) systems with 2D (stereo) [ 122 ] and 3D configurations [ 123 ] have been proposed. These consist of two or three cameras placed at a fixed location, which record the TMS treatment; sets of passive (IR reflectors [ 45 , 48 ], QR codes [ 123 ], etc.…”