A method and device for applying a radioactive source to a tissue site is disclosed. The device facilitates the precise placement of, for example, 125Iodine seeds relative to the surgical margin, assures the seeds remain fixed in their precise position for the duration of the treatment, overcomes the technical difficulties of manipulating the seeds through the narrow surgical incision, and reduces the radiation dose to the clinicians. The device incorporates the radioactive seeds into a fastening means, preferably surgical staples, used in the surgical procedure. In this way, the seeds are concurrently secured in position directly adjacent to the surgical resection and remain immobile.