An antenna system for tissue ablation includes an energy transmission member, a conductive hollow coil member coupled to the energy transmission member, and a fluid cooling system coupled to the conductive hollow coil member for providing a flow of cooling fluid through a member lumen of the conductive hollow coil member for cooling the conductive hollow coil member. In some examples, at least one of the antenna body, a choke member, and a hybrid choke member includes the conductive hollow coil member. In some examples, the hybrid choke member includes a choke portion wound around a portion of the energy transmission member, an antenna body portion wound around a portion of the energy transmission member, and an insulator portion extending between the choke portion and the antenna body portion. In some examples, the antenna system includes a sheath extending over the energy transmission member and the conductive hollow coil member.
