Candoo Systems instrument

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MEG System – Brief Description, Its Advantages and Difference from EEG System

Both MEG and EEG systems are used to monitor the brain activity but still, there are some differences between these two sensing devices. MEG is a functional neuroimaging technique used for mapping brain activity by recording magnetic field produced naturally in the brain. Whereas EEG is an electrophysiological monitoring method used to measure the activity of the brain by recording the electrical fields. If you also want to purchase MEG/EEG sensors you can ask the local distributor, who provides remarkable magnetic sensing devices, MEG/EEG consulting and magnetic field site surveys. 

Let’s discuss in detail about MEG systems and how is it different from the EEG and MRI:

What is an MEG System?

Magnetoencephalography (MEG) is a non-invasive sensor used for investigating the human brain activity. It is capable of measuring ongoing brain activity on a millisecond-by-milliseconds basis and for this very sensitive magnetometers are used.

How Does MEG Scanner Works?

At the cellular level, individual neurons in the brain have electrochemical characteristics that cause the flow of electrically charged ions through a cell. As the neuromagnetic signals that are produced by the net effect of the slow ionic current flow are very small. For effective working MEG sensors require (SQUID) superconducting quantum interference device is kepy in a big liquid helium cooling unit which is set at approximately -269 degrees C. This is necessary to do as it helps SQUID devices in detecting and amplifying magnetic fields generated by neurons effectively.

Advantages of MEG Over EEG and fMRI Systems:

MEG has more benefits than fMRI and EEG. As MEG provides timing as well as spatial information about brain activity. fMRI(Functional Magnetic Resonance Imaging or functional MRI )measures the oxygenation of the blood flowing near the active neurons and the activity of the brain is reflected indirectly by fMRI signals. While MEG signals are obtained directly from neuronal electrical activity and are able to show absolute neuronal activity.

The main advantage of MEG system is that signal produced can be recorded in sleeping subjects; however, this is not the case with the fMRI system. With fMRI there is no involvement of head movements during recording, while in MEG measurement one can move their heads within the MEG helmet.

Moreover, MEG sensors provide more accurate spatial localization of neural activities than EEG, a complementary method of recording brain activity. So all MEG/EEG consulting companies prefer to choose these devices rather than other sensing instruments.

Most importantly, MEG provides a right temporal information about the brain activation with sub-millisecond precision. Whereas fMRI and EEG measurement provide a poor temporal information.

Difference between MEG and EEG Systems:

MEG and EEG are closely related but you will still find some differences, which are as follow -

EEG detects the electric signals generated by the neural currents instead of the corresponding magnetic fields.

Most important difference is that the skull and the tissue around the brain gets affected with the magnetic fields when monitored by MEG which is much less than they get affected with the electrical impulses measured by EEG scanners.

MEG results in better spatial resolution, as magnetic fields are less distorted by tissues of different conductivity as compared to the electric potential measured with electroencephalography (EEG).

Data interpretation is easier in MEG and it detects only tangential current. Whereas EEG detects both radial and tangential currents.

MEG primarily detects intracellular currents whereas EEG is sensitive to extracellular volume currents.

You have the complete information about the MEG and EEG systems, so whenever you visit a MEG/EEG consulting companies for buying sensing devices you can judge the difference and can choose a right device according to your need.

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How does Fluxgate Magnetometer work?

You must be aware of the fact that magnets create a magnetic field. And earth has a magnetic field, similarly, a current flowing in a wire also has a magnetic field. However, did you ever know that our brain and heart also generates a field around itself? Even a fluxgate magnetometer has a magnetic field around it. However, there is a difference between a magnetic field generated by a magnet and by brain and heart is in the magnitude of magnetic.

To your surprise, we are surrounded by magnetic fields. Earth also has its own magnetic field, although it is relatively small in comparison to others.

Defining Magnetometer

It is a device that measures magnetic fields. It has the capability with a sensor that measures flux density. It refers to sensors used for sensing magnetic areas or measures magnetic field with the help of one or more sensors.

The flux of the magnet is directly proportion to magnetic field strength, and thus it detects the fluctuation in the earth’s field.

Defining Fluxgate

A fluxgate magnetometer is a magnetic field sensor used for vectormagnetic field. Its range is appropriate for measuring earth’s field and is capable of resolving until the limit of 10000. It was traditionally used for compass work and navigation along with metal detection and prospecting. However, in today’s world of silicon, its importance is fading.

It can be categorized into two types – magnetometer with rode cores and ring cores. The fluxgate uses a highly permeable core, which concentrates on the magnetic field that needs to be measured. The core is saturated magnetically in opposite direction with help of a suitable axis. This is done with a help of an excitation coil driven by a square waveform.

How does Magnetometer work?

The magnet is distorted by magnetic flux lines thus, some materials are said to be magnetic in nature. Such materials create distortion in the earth’s magnetic flux that forms around it. The instrument analyzes these distortions.

A magnetometer job is to measure magnetic flux density at the point where the sensor is located. Magnetic field reduces in intensity with the cube of the distance from the object. The distance of that can be detected by this instrument is directly proportionate to the cube root of the magnetometer’s sensitivity.

Here are the types found:

1.      Vector Magnetometer measures the flux density value of a specific direction in 3-dimensional space.

2.      Scalar Magnetometer measures only the magnitude of the vector through the sensor, without considering the direction.   

    

The flux of change from Faraday’s law that is proportionate to the magnetic field – an ordinary sensor can be used for this. This technique is used for various kinds of experiments and studies, based on which many results are taken. Fluxgate magnetometer is also used for research around the world.  

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