A device for directing energy to a target volume of tissue includes an antenna assembly and an elongated body member. The elongated body member includes a proximal end portion and a distal end portion, wherein the proximal and distal end portions define a longitudinal axis. The elongated body member has a chamber defined therein that extends along the longitudinal axis, and a body wall surrounding the chamber. An antenna assembly is disposed in the chamber. The elongated body member also includes an opening in the body wall to allow energy radiated from the antenna assembly to transfer into the target volume of tissue.