Magnetoencephalography (MEG) is the measurement of extracranial magnetic fields generated by intracellular electric currents in the brain. It offers the possibility to locate discrete source of normal and pathological electrical activity with three-dimensional accuracy of a few millimeters. Current applications include epileptogenic foci localization, evoked response studies, and cognitive processing research. MEG promises to become an important noninvasive spatial imaging modality that reveals dynamic electrical function of the brain. This project addresses a major source of uncertainty in locating the volume of brain tissue responsible for the measured fields, namely the difficulty in accurately positioning the MEG sensor with respect to the skull. The current positioning systems are too imprecise and so slow and difficult to use that they limit the feasibility of MEG for many of the most promising applications where hour-long measurement sessions will not be tolerated. All aspects of the problem are addressed. These include a gantry to position and support the MEG senor, a combined patient support table and chair, means to accurately read the sensor position relative to the head, and a text fixture (phantom) to verify system performance.
