WHAT IS MEG?: MEG Site Example

A Clinical MEG Laboratory

University of Alabama, Birmingham

An MEG laboratory is a highly sophisticated integrated suite of components for recording and analyzing extremely small magnetic signals in a clinical environment. The system is manufactured and integrated at the 4-D Neuroimaging factory and installed in the hospital as a turn-key, stand-alone system.

The largest component of an MEG laboratory is the Magnetically Shielded Room (MSR). The MSR is constructed from a material called µ-metal (mostly nickel), and provides an extremely effective shield against environmental magnetic noise (cars, electrical power lines, etc.). The MSR is normally covered with paneling on the outside to provide a pleasant atmosphere, or it has a wall built around it to integrate the MSR into the clinical environment.

The electronics systems necessary for recording magnetic activity from the patient are located outside the MSR. These systems include the MEG amplification and data-acquisition system, EEG recording system (typically included) and stimulation system controllers.

Also located outside the MSR are the computer console used by the operator to perform the study and various computer workstations for analyzing the data.

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The patient enters the MSR through the MSR door, which resembles a vault door, but opens and closes easily with a pneumatic assist. It can be opened from either the inside or outside. Housed in the MSR is the MEG sensor, which is comprised of an array of detector coils cooled with liquid helium (-269∫ C) and contained within an insulating Dewar. All devices and materials within the MSR must be non-magnetic and must not produce magnetic fields that could interfere with the recordings. The interior of the MSR is lit and has a quiet, soothing atmosphere. During an MEG study, the patient is comfortably positioned within the MSR on the patient support system, in either a seated or supine position. While in the MSR the patient is monitored by closed circuit monitor and intercom at all times.

For most clinical studies, the support system is configured as a bed, and the patient lies on the bed in a supine position. The sensor is rotated into position such that the detector array surrounds the patientís head. A head and neck support further ensures patient comfort. In many studies, the patient is encouraged to sleep. This is generally successful.

Once the data has been collected and the patient has been dismissed, the technologist and physician analyze the data using one of the workstations supplied with the MEG system, or other computer systems. The MEG system is normally tied in with the hospital information network so that MRI images and other diagnostic information are available.

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