Devices and techniques for permanent application of radioactive sources in the field of brachytherapy are described. In an embodiment, an implantable device for radiation therapy of pathological tissues directed toward the administration of radiation to tissue adjacent a cavity wall or surgical excision. The device may include an insertable member, such as a substantially cylindrical member, having at least two ends, a central section positioned between the ends, and a fixation element to retain the implantable device implanted in tissue at a desired position. The device may further include a radioactive source at least partially positioned within the insertable member and that is disposed to deliver radiation to a desired area.