1. A system for estimating a volume of activation using a set of electrical stimulation settings, the system comprising: a processor configured to: receive electric field data and the set of electrical stimulation settings for use with a non-cylindrically symmetrical implanted leadwire; apply the electric field data and the set of electrical stimulation settings to a volume of activation estimation model to determine a value for each of one of more locations for each of a plurality of neural elements, wherein the volume of activation estimation model either 1) does not use as input a plurality of sets of values of an electrical field at different points in time, 2) includes only linear equations generated based on observed functioning of a model that uses differential equations, or 3) does not use more than one differential equation; output an indication of an estimated volume of activation based on the values for each of the one or more locations for each of the neural elements; and initiate a signal to convey the set of electrical stimulation settings to an implanted pulse generator to transmit signals via a leadwire for stimulation of patient tissue according to the set of electrical stimulation settings.