An electrode assembly for a catheter system has a longitudinal axis, a proximal end and a distal end. Multiple struts extend coextensively with each other from the proximal end to the distal end of the electrode assembly. Each strut carries an electrode spaced longitudinally from the proximal end of the electrode assembly. The longitudinal spacing of one electrode from the proximal end of the electrode assembly is different from the longitudinal spacing of another electrode from the proximal end of the electrode assembly. The electrode assembly is configurable between a collapsed configuration and an expanded configuration, with the electrodes being transversely spaced from the longitudinal axis of the electrode assembly a greater distance in the expanded configuration than in the collapsed configuration. In the expanded configuration, the electrodes are transversely spaced from the longitudinal axis of the electrode assembly approximately the same distance.
