Magnetoencephalography (MEG) is the measurement of extracranial magnetic fields generated by intracellular electric currents in the brain. It offers the possibility to locate discrete sources 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 hours-long measurement sessions will not be tolerated. An accurate electromagnetic MEG sensor position measuring system is proposed for development in Phase I. The same technology will be used to establish the coordinate system and measure the head shape parameters required to solve the source location probelm. Phase II will build on these results to develop an improved patient/sensor positioning apparatus suitable for clinical use.
