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|Below you will find a short description of [#Magsgrads magnetometers and gradiometers], as well as our [#MEGsensors MEG sensor] and [#EEGlabels EEG electrode] layouts.||Below you will find a short description of [[#Magsgrads|magnetometers and gradiometers]], as well as our [[#MEGsensors|MEG sensor]] and [[#EEGlabels|EEG electrode]] layouts.|
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|The [#Elektamanuals Elekta manuals] are at the bottom.||The [[#Elektamanuals|Elekta manuals]] are at the bottom.|
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|Figures are from the Elekta Neuromag System [attachment:HardwareUser.pdf Hardware User's Manual].||Figures are from the Elekta Neuromag System [[attachment:HardwareUser.pdf|Hardware User's Manual]].|
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|[attachment:HardwareTechnical.pdf Hardware Technical Manual]||[[attachment:HardwareTechnical.pdf|Hardware Technical Manual]]|
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|[attachment:HardwareUser.pdf Hardware User's Manual]||[[attachment:HardwareUser.pdf|Hardware User's Manual]]|
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|[attachment:DataAcquisition.pdf Data Acquisition Manual]||[[attachment:DataAcquisition.pdf|Data Acquisition Manual]]|
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|[attachment:StimulusSystem.pdf Stimulus System Manual]||[[attachment:StimulusSystem.pdf|Stimulus System Manual]]|
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|[attachment:SensorTuner.pdf Sensor Tuner Manual]||[[attachment:SensorTuner.pdf|Sensor Tuner Manual]]|
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|[wiki:CbuMeg:StandardOperatingProcedures Standard Operating Procedures]||[[StandardOperatingProcedures|Standard Operating Procedures]]|
The Elekta Neuromag Vectorview System
The Elekta manuals are at the bottom.
Figures are from the Elekta Neuromag System Hardware User's Manual.
Our Vectorview systems contains 102 magnetometers and 204 planar gradiometers. Magnetometers consist of a single coil which measures the magnetic flux perpendicular to its surface. Planar gradiometers consist of a "figure-of-eight"-type coil configuration. The measured signal is the difference between the two loops of the "eight", or the spatial gradient. There are two orthogonal planar gradiometers at each location. This arrangement is illustrated in the following figure (black: magnetometer; grey and white: two gradiometers).
It has been shown that 3 sensors of these types at one location measure independent information (their "leadfields" are orthogonal). It is therefore more efficient than placing 3 sensors of the same type (e.g. magnetometers) close to each other (they would basically measure the same signal 3 times). Our sensor configuration therefore provides an optimal sampling of the magnetic field for a given number of sensors. The downside is that magnetometers and gradiometers often have to be treated differently during analysis or visualisation.
This is the whole sensor layout, including the sensor labels used by the Neuromag software:
We routinely use a 70-electrode EEG set-up (Easycap) in combination with our MEG recordings. This is the electrode layout: