Calibration of a Coil Array Geometry Using an X-Ray Computed Tomography

Sensor layout of biomagnetic measurement systems is measured using a multiple coil array that generates a magnetic signal. However, the results of the sensor array measurement included the error of the coil array because the coil array was not calibrated. In this article, we proposed a calibration method to obtain the effective geometry and uncertainty of the coil array. The calibration was performed based on the X-ray computed tomography (CT) measurements and numerical analysis of the position and shape of the coils. The differences between the designed and calibrated coil array geometries were 0.6 mm, 0.7°, and 0.3 mm with respect to the center position, orientation of the normal vector, and radius of the coils, respectively. The uncertainty of the calibration was 0.3 mm and 1.7° in terms of the dimension and orientation, respectively. We measured the sensor array layout of a magnetoencephalography (MEG) system using a calibrated coil array geometry. The source localization accuracy of the MEG system was improved compared with that of the sensor array layout obtained using the designed coil array geometry. We revealed the necessity of calibrating the coil array, regardless of the precision of the fabrication.