Abstract: This disclosure is directed to a catheter having a dual node multiray electrode assembly at the distal end of the catheter body. The dual node multiray electrode assembly includes a proximal multiray array with a plurality of spines connected at one end, each spine having at least one ablation electrode, and a distal node. The dual node multiray electrode assembly may have an expanded configuration and a collapsed configuration wherein the spines are arranged generally along a longitudinal axis of the catheter body. The distal node may be configured to be deployed within a vessel and the proximal multiray array may be configured to engage tissue forming an ostium of the vessel with the ablation electrodes. In some embodiments, the relative distance between the proximal multiray array and the distal node is adjustable.