Limits...
Using a motion capture system for spatial localization of EEG electrodes.

Reis PM, Lochmann M - Front Neurosci (2015)

Bottom Line: It acquires 3D coordinates of each electrode and automatically labels them.Each electrode has a small reflector on top of it thus allowing its detection by the cameras.The measurement was quickly performed and all positions were captured.

View Article: PubMed Central - PubMed

Affiliation: Department of Sports and Exercise Medicine, Institute of Sport Science and Sport, Friedrich-Alexander-University Erlangen-Nuremberg Erlangen, Germany.

ABSTRACT
Electroencephalography (EEG) is often used in source analysis studies, in which the locations of cortex regions responsible for a signal are determined. For this to be possible, accurate positions of the electrodes at the scalp surface must be determined, otherwise errors in the source estimation will occur. Today, several methods for acquiring these positions exist but they are often not satisfyingly accurate or take a long time to perform. Therefore, in this paper we describe a method capable of determining the positions accurately and fast. This method uses an infrared light motion capture system (IR-MOCAP) with 8 cameras arranged around a human participant. It acquires 3D coordinates of each electrode and automatically labels them. Each electrode has a small reflector on top of it thus allowing its detection by the cameras. We tested the accuracy of the presented method by acquiring the electrodes positions on a rigid sphere model and comparing these with measurements from computer tomography (CT). The average Euclidean distance between the sphere model CT measurements and the presented method was 1.23 mm with an average standard deviation of 0.51 mm. We also tested the method with a human participant. The measurement was quickly performed and all positions were captured. These results tell that, with this method, it is possible to acquire electrode positions with minimal error and little time effort for the study participants and investigators.

No MeSH data available.


Related in: MedlinePlus

On top, a slice of the fiberglass sphere CT scan. The solid yellow arrow points at a sectioned electrode with a reflector on top. On the bottom, images of the sphere's reconstructed surface. On the left, and on the right a close up of an electrode. The pictures shows the reconstructed surface of the sphere and electrodes, obtained from the scan slices. The areas of red text are coordinates that are displayed when an investigator clicks on a part of the digitized model, in this case the top surface of the reflector markers. On the right, we can see the electrode with its reflector and corresponding displayed coordinates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4403350&req=5

Figure 6: On top, a slice of the fiberglass sphere CT scan. The solid yellow arrow points at a sectioned electrode with a reflector on top. On the bottom, images of the sphere's reconstructed surface. On the left, and on the right a close up of an electrode. The pictures shows the reconstructed surface of the sphere and electrodes, obtained from the scan slices. The areas of red text are coordinates that are displayed when an investigator clicks on a part of the digitized model, in this case the top surface of the reflector markers. On the right, we can see the electrode with its reflector and corresponding displayed coordinates.

Mentions: Next, we proceeded with data collection. We scanned the sphere with a calibrated Siemens Somatom Definition AS X-Ray Computerized Tomograph (Siemens AG, Erlangen, Germany). For the CT scan we used the HeadSpiral 0.6 mm H70h protocol that resulted in 318 slices. This provided a very clean, artifact free imaging of the sphere. The top picture of Figure 6 shows one slice of the sphere resultant from the scan. Afterwards, in a room nearby, we collected data using the SSDEL method with 8 cameras as previously described in Section 2. The system was calibrated by means of wand calibration. Data was collected using the Track Manager software with 100 Hz sample rate and 10 s capture time.


Using a motion capture system for spatial localization of EEG electrodes.

Reis PM, Lochmann M - Front Neurosci (2015)

On top, a slice of the fiberglass sphere CT scan. The solid yellow arrow points at a sectioned electrode with a reflector on top. On the bottom, images of the sphere's reconstructed surface. On the left, and on the right a close up of an electrode. The pictures shows the reconstructed surface of the sphere and electrodes, obtained from the scan slices. The areas of red text are coordinates that are displayed when an investigator clicks on a part of the digitized model, in this case the top surface of the reflector markers. On the right, we can see the electrode with its reflector and corresponding displayed coordinates.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4403350&req=5

Figure 6: On top, a slice of the fiberglass sphere CT scan. The solid yellow arrow points at a sectioned electrode with a reflector on top. On the bottom, images of the sphere's reconstructed surface. On the left, and on the right a close up of an electrode. The pictures shows the reconstructed surface of the sphere and electrodes, obtained from the scan slices. The areas of red text are coordinates that are displayed when an investigator clicks on a part of the digitized model, in this case the top surface of the reflector markers. On the right, we can see the electrode with its reflector and corresponding displayed coordinates.
Mentions: Next, we proceeded with data collection. We scanned the sphere with a calibrated Siemens Somatom Definition AS X-Ray Computerized Tomograph (Siemens AG, Erlangen, Germany). For the CT scan we used the HeadSpiral 0.6 mm H70h protocol that resulted in 318 slices. This provided a very clean, artifact free imaging of the sphere. The top picture of Figure 6 shows one slice of the sphere resultant from the scan. Afterwards, in a room nearby, we collected data using the SSDEL method with 8 cameras as previously described in Section 2. The system was calibrated by means of wand calibration. Data was collected using the Track Manager software with 100 Hz sample rate and 10 s capture time.

Bottom Line: It acquires 3D coordinates of each electrode and automatically labels them.Each electrode has a small reflector on top of it thus allowing its detection by the cameras.The measurement was quickly performed and all positions were captured.

View Article: PubMed Central - PubMed

Affiliation: Department of Sports and Exercise Medicine, Institute of Sport Science and Sport, Friedrich-Alexander-University Erlangen-Nuremberg Erlangen, Germany.

ABSTRACT
Electroencephalography (EEG) is often used in source analysis studies, in which the locations of cortex regions responsible for a signal are determined. For this to be possible, accurate positions of the electrodes at the scalp surface must be determined, otherwise errors in the source estimation will occur. Today, several methods for acquiring these positions exist but they are often not satisfyingly accurate or take a long time to perform. Therefore, in this paper we describe a method capable of determining the positions accurately and fast. This method uses an infrared light motion capture system (IR-MOCAP) with 8 cameras arranged around a human participant. It acquires 3D coordinates of each electrode and automatically labels them. Each electrode has a small reflector on top of it thus allowing its detection by the cameras. We tested the accuracy of the presented method by acquiring the electrodes positions on a rigid sphere model and comparing these with measurements from computer tomography (CT). The average Euclidean distance between the sphere model CT measurements and the presented method was 1.23 mm with an average standard deviation of 0.51 mm. We also tested the method with a human participant. The measurement was quickly performed and all positions were captured. These results tell that, with this method, it is possible to acquire electrode positions with minimal error and little time effort for the study participants and investigators.

No MeSH data available.


Related in: MedlinePlus