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Scope:
Development of a PC based EEG System to monitor brain activity during an f-MRI (functional MRI) scan.
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Description:
There are numerous systems of EEG recorders available, such as strip chart recorders and even PC based acquisition system. These “conventional” system are not designed to work under the extreme conditions that occur during an MRI scan. A static magnet field of about 3 Tesla is present among transient noise produced by the actual scan. The electrodes attached to the human body and their connection wire are exposed to these harsh EMI conditions.It is almost impossible to produce usable signals under these conditions with conventional systems.
Theory:
In order to monitor electrical brain activity produced during an f-MRI scan, special measures have to be taken. In order to be able to recover the usable signal levels contaminated with noise created by the MRI Scanner, a special algorythm needs to be used to mathematically filter out the signals of interest. This technique requires a high precision trigger mechanism for the data acquistion to assure a phase stabilized recording.