FACTORS AFFECTING THE ACCURACY OF THE BOUNDARY-ELEMENT METHOD IN THE FORWARD PROBLEM .1. CALCULATING SURFACE-POTENTIALS

A comprehensive review of factors affecting the accuracy of the bounda ry element method (BEM) for calculating surface potentials is presente d. A relative-error statistic is developed which is only sensitive to calculation errors that could affect the inverse solution for source p osition, and insensitive to errors that only affect the solution for s ource strength. The factors considered in this paper are: numerical ap proximations intrinsic to the BEM, such as constant-potential versus l inear-potential basis functions and sharp-edged versus smooth-surfaced volumes; aspects of the volume conductor including the volume shape, density of surface elements, and element shape; source position and or ientation; and effects of ''refinements'' in the numerical methods. Th e effects of these factors are considered in both smooth-shaped (spher es and spheroids) and sharp-edged (cubes) volume conductors. This repr esents the first attempt to assess the effects of many of these factor s pertaining to the numerical methods commonly used in fields such as electrocardiography (ECG) and electroencephalography (EEG). Strategies for obtaining the most accurate solutions are presented.