Antenna systems and methods of use

An antenna system for tissue ablation includes an energy transmission member, a conductive hollow coil member, and a fluid cooling system. The energy transmission member has an inner conductor, an outer conductor, and a dielectric layer between the inner and outer conductors. A portion of the dielectric layer extends distally of a distal end of the outer conductor. The conductive hollow coil member includes a member lumen within a length of the conductive hollow coil member. The conductive hollow coil member is coiled around the portion of the dielectric layer and is separate from the inner conductor. The conductive hollow coil member extends along an entire length of the outer conductor of the energy transmission member. The fluid cooling system is coupled to the conductive hollow coil member for providing a flow of a cooling fluid through the member lumen for cooling the conductive hollow coil member.