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A numerical model of a human torso was used to study and compare the effect of outer torso, lung, and intracavitary blood mass boundaries on the body surface distribution of electric potential and normal component of magnetic field due to a single current dipole placed at various locations in the heart. Results are presented in the form of isopotential and isofield maps and are also compared to the maps of a dipole in a semi-infinite homogenous model in the context of single dipole inverse solutions. The inclusion of the boundaries has a large effect on the magnitudes of the maps and modest effects on their topology. The electric and magnetic maps show similar responses to the boundaries for X (leftward) and Y (upward) directed dipoles. The electric maps of Z (back-to-front) dipoles are comparatively unaffected by the boundaries, unlike the magnetic maps of Z dipoles, to which the outer boundary makes a substantial contribution. The results indicate electric and magnetic maps have complementary sensitivities for certain dipole components in the presence of realistic boundaries.
Date of Publication: Sept. 1988