Source localization in an inhomogeneous physical thorax phantom

The influence of lung inhomogeneities on focal source localizations in elec trocardiography (ECG) and magnetocardiography (MCG) is investigated. A realistically shaped physical thorax phantom with cylindrical lung inhomo geneities is used for electric and magnetic measurements. The lungs are mod elled with a special ionic exchange membrane which allows different conduct ivity compartments without influencing the free ionic current how. The dipo lar current sources are composed of platinum wire and located at different depths and directions between the lung inhomogeneities. We localized the cu rrent dipoles with different boundary element method (BEM) models, based on electrical data and simultaneous electrical and magnetic data. Our results indicate the possibility of superadditive information gain by combining el ectrical and magnetic data for source reconstructions. We found a significant influence of the inhomogeneities on both the calcula ted source location and the calculated sourer strength. Mislocalizations of up to 16 mm and wrong dipole strengths of up to 52% were obtained when the lung inhomogeneities were not taken into account for source localization. Dipoles parallel to the lungs showed a larger localization error in depth t han dipoles perpendicular to the lungs. We conclude that the incorporation of lung inhomogeneities will improve sou rce localization accuracy in ECG and MCG.