Magnetoencephalography with diversely oriented and multicomponent sensors

To locate endocranial current sources, a magnetoencephalography (MEG) system usually measures the magnetic field at many points around the skull with an array of radial sensors. Despite the success of using radial components of the field, we show that using nonradial components may potentially also be beneficial. We demonstrate some benefits of using diversely oriented and multicomponent sensors to measure the nonradial components. A framework is provided for analyzing the accuracy of a system that estimates the location and direction of a current dipole inside a spherical skull. The framework is then used to determine the effect on accuracy of varying the orientations of sensors in an array and, as a consequence, it is found that the radial orientations commonly used in practice are suboptimal for locating dipoles near the array's center. A diversely oriented array that improves performance is presented. We show how a single multicomponent sensor can locate a dipole, and derive a simple algorithm for locating a dipole near the sensor.