VectorviewDescription - Meg Wiki
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The Elekta Neuromag Vectorview System

Below you will find a short description of magnetometers and gradiometers, as well as our MEG sensor and EEG electrode layouts.

The Elekta manuals are at the bottom.

Figures are from the Elekta Neuromag System Hardware User's Manual.

Technical description

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).

MagsGrads.jpg

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:

SensorLayout.jpg

SensorLabeling.jpg

We routinely use a 70-electrode EEG set-up (Easycap) in combination with our MEG recordings. This is the electrode layout:

ElectrodeLayout.jpg

Elekta Manuals

Hardware Technical Manual

Hardware User's Manual

Data Acquisition Manual

Stimulus System Manual

Sensor Tuner Manual

Standard Operating Procedures

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