A comparison of zero and first order Tikhonov regularization for an inhomogeneous volume

In this study, we examine the effects of tissue inhomogeneities on epicardial estimates when using zero-order Tikhonov and first-order Tikhonov regularization. Epicardial potentials measured during an in-vivo swine experiment were projected to 96 body surface locations using an inhomogeneous transfer matrix constructed using a finite-element model of the swine made from CT scans. It was assumed that the lungs, fat and remaining volume had conductivities of 50, 40 and 220 μmho/mm. The inverse estimates were then computed from the body surface potentials where noise had been added to simulate measurement errors. The inverses were computed using the same inhomogeneous transfer matrix used for the the forward projection, and with a homogeneous transfer matrix