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The stability of source localization in a whole-head magnetoencephalography system demonstrated by auditory evoked field measurements
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10.1063/1.3641991
/content/aip/journal/jap/110/7/10.1063/1.3641991
http://aip.metastore.ingenta.com/content/aip/journal/jap/110/7/10.1063/1.3641991

Figures

Image of FIG. 1.
FIG. 1.

(Color online) The definition of subject’s head coordinate.

Image of FIG. 2.
FIG. 2.

(Color online) (a) The photo of a subject wearing the four localization coils on the vertex. (b) The relative positions of three anatomical landmarks (nasion, PAL, PAR) and four localization coils recorded by the tracking system are marked in the subject’s head coordinate.

Image of FIG. 3.
FIG. 3.

(Color online) (a) The magnetic field distribution generated from the localization coil 1 and recorded by the SQUID gradiometers. The magnetic field distribution can be used to inversely calculate the position of localization coil relative to SQUID sensors. (b) The calculated positions of four localization coils relative to SQUID sensors. The points are the calculated positions of four localization coils and the black circles are representative of SQUID sensors. (Top view). (c) After the coordinate transformation, the positions of three anatomical landmarks, four localization coils, and SQUID sensors are integrated and marked in the subject’s head coordinate. Also shown are the calculated positions of four localization coils relative to SQUID sensors in square configuration in (b), which are coincided with positions of four localization coils marked in the subject’s head coordinate. (Top view) (d) Incorporating with the subject’s virtual head constructed from the MRI data, the subject’s head position within the MEG helmet is precisely determined (front view).

Image of FIG. 4.
FIG. 4.

(Color online) (a) The butterfly plot and (b) the MGFP curve of the measured AEFs. Identifying from the MGFP curve, the peak latency of N100 m and P200 m are 100 ms and 203 ms after the onset of sound stimulus, respectively. The magnetic contour maps of N100 m and P200 m at the peak latency are shown in (c) and (d). In (c) the direction of magnetic fields in the left lower-contours and right-upper contours is away from the head while the direction of magnetic fields in the left upper-contours and right lower-contours points into the head. In (d) the direction of magnetic fields in the left lower-contours and right-upper contours points into the head while the direction of magnetic fields in the left upper-contours and right lower-contours is away from the head. The interval of the contour is 20 fT and the points are representative of SQUID sensors.

Image of FIG. 5.
FIG. 5.

(Color online) The calculated ECD locations of N100 m signal at the peak latency are marked on the subject’s MRI. (a) Coronal plane, (b) transverse plane, (c) sagittal plane at left temporal lobe, and (d) sagittal plane at right temporal lobe.

Image of FIG. 6.
FIG. 6.

(Color online) The calculated ECD locations of P200 m signal at the peak latency are marked on the subject’s MRI. (a) Coronal plane, (b) transverse plane, (c) sagittal plane at left temporal lobe, and (d) sagittal plane at right temporal lobe.

Image of FIG. 7.
FIG. 7.

(Color online) The averaged ECD positions and standard deviations of N100 m, which were calculated from 9 sets of AEF data, are shown on the (a) coronal plane and (b) transverse plane of subject’s MRI. The error bars show the ranges of one standard deviation.

Image of FIG. 8.
FIG. 8.

(Color online) (a) The schema of the phantom experiment setup. (b) A 2D magnetic contour map generated from the line segment at the vertex.

Tables

Generic image for table
Table I.

The errors between the calculated positions and actual positions of the line segment at the three test points.

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/content/aip/journal/jap/110/7/10.1063/1.3641991
2011-10-14
2014-04-18
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: The stability of source localization in a whole-head magnetoencephalography system demonstrated by auditory evoked field measurements
http://aip.metastore.ingenta.com/content/aip/journal/jap/110/7/10.1063/1.3641991
10.1063/1.3641991
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