MCG inverse solution: influence of coil size, grid size, number of coils, and SNR

Model studies were used to assess quantitatively the influence of gradiometer coil size, number of measurement points, size of measurement grid and signal-to-noise ratio (SNR) on the accuracy of the inverse solution from a magnetocardiogram. The human torso was modeled by an infinite half-space and the inverse solution was calculated by a moving dipole procedure. The most crucial parameter for inverse solution accuracy is the SNR. Up to a coil radius of 4 cm, the increasing SNR balances the loss due to field averaging, and the inverse solution is improved accordingly. A reasonable number of measurement points is about 15; using more points does not improve the inverse solution appreciably. in multichannel systems, grid size is limited by the size of the dewar. It is found that grid size is not crucial in the inverse solution; optimum size is an area of approximately 200-300 cm ².