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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

Image of the Human volunteer sitting during image acquisition wearing a modified 64 Channel actiCAP EEG cap.
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Figure 7: Image of the Human volunteer sitting during image acquisition wearing a modified 64 Channel actiCAP EEG cap.

Mentions: We measured electrodes positions from a volunteer to test this method feasibility in acquiring electrode positions from a human head. Data collection from the volunteer was approved by the ethics committee of the Friedrich-Alexander University Erlangen-Nürnberg. We also obtained written informed consent from the volunteer before conducting this experiment. The system acquired electrodes positions from the human volunteer wearing a modified 64 Channel actiCAP EEG cap (Figure 2), plus reference, ground electrode and three anatomic reference markers. An expert placed the anatomic reference reflective markers on the volunteer's head by accurately palpating the area and identifying the mastoid process and the tragus. During image capturing, we used a sample rate of 100 Hz for 10 s. All points were captured without noise. As the reader can observe on Figure 7 the volunteer was sitting on a chair during the measurement. We can also see one of the anatomic reference markers and that are no free electrode cables interfering with image acquisition. We proceeded to reference the coordinates to the head coordinate system and co-registering the obtained points with the volunteer's individual anatomy by using the reference anatomic points in the procedure explained earlier in Section 2.


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

Reis PM, Lochmann M - Front Neurosci (2015)

Image of the Human volunteer sitting during image acquisition wearing a modified 64 Channel actiCAP EEG cap.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: Image of the Human volunteer sitting during image acquisition wearing a modified 64 Channel actiCAP EEG cap.
Mentions: We measured electrodes positions from a volunteer to test this method feasibility in acquiring electrode positions from a human head. Data collection from the volunteer was approved by the ethics committee of the Friedrich-Alexander University Erlangen-Nürnberg. We also obtained written informed consent from the volunteer before conducting this experiment. The system acquired electrodes positions from the human volunteer wearing a modified 64 Channel actiCAP EEG cap (Figure 2), plus reference, ground electrode and three anatomic reference markers. An expert placed the anatomic reference reflective markers on the volunteer's head by accurately palpating the area and identifying the mastoid process and the tragus. During image capturing, we used a sample rate of 100 Hz for 10 s. All points were captured without noise. As the reader can observe on Figure 7 the volunteer was sitting on a chair during the measurement. We can also see one of the anatomic reference markers and that are no free electrode cables interfering with image acquisition. We proceeded to reference the coordinates to the head coordinate system and co-registering the obtained points with the volunteer's individual anatomy by using the reference anatomic points in the procedure explained earlier in Section 2.

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