A microwave ablation antenna assembly includes an elongate body that extends from a first end to a second end thereof, and which defines therein a hollow inner volume and a longitudinal axis of the antenna. The ablation antenna assembly includes an applicator tip portion mounted on the second end of the elongate body, an elongate coaxial conductor assembly for connection to a source of microwave energy, a dipole tip portion that extends from the feed point of the coaxial conductor assembly towards the applicator tip, and a choke assembly with first and second choke conductors.