CALCULATION OF ELECTRICAL POTENTIALS ON THE SURFACE OF A REALISTIC HEAD MODEL BY FINITE-DIFFERENCES

We present a method for the calculation of electrical potentials at th e surface of realistic head models from a point dipole generator based on a 3D finite-difference algorithm. The model was validated by compa ring calculated values with those obtained algebraically for a three-s hell spherical model. For a 1.25 mm cubic grid size, the mean error wa s 4.9% for a superficial dipole (3.75 mm from the inner surface of the skull) pointing in the radial direction. The effect of generator disc retization and node spacing on the accuracy of the model was studied. Three values of the node spacing were considered: 1, 1.25 and 1.5 mm. The mean relative errors were 4.2, 6.3 and 9.3%, respectively. The qua lity of the approximation of a point dipole by an array of nodes in a spherical neighbourhood did not depend significantly on the number of nodes used. The application of the method to a conduction model derive d from MRI data is demonstrated.