**Fig. 11.11.** Construction of the image surface for a source point at a volume conductor of arbitrary shape, illustrated in two dimensions. A one-to-one relation is established between points on the surface of the volume conductor and the image surface.

(A) Unit vectors are placed at the source location.

(B) By measuring the corresponding potentials at each surface point, the lead vector can be determined.

(C) The locus described by the family of lead vectors form the image surface.