Applications of multipole expansion.

With use of a homogeneous torso model, dipole and quadrupole sensitivity was determined for unipolar leads from many sites on the thoracic surface. Representatives of non-dipolar maps were obtained from the sensitivity of each of unipolar leads to the 5 rectangular components of the quadrupole. Over-all sensitivity to the quadrupole or the magnitude of the lead tensor was calculated from the measurements and mapped over the torso surface. This map indicates relative proximity of the thoracic surface and gives a theoretical basis for the selection of electrode locations in the surface mapping technique.