#$%^&*AU2010201870B220120426.pdf#####ABSTRACT A method of manufacturing a radiotherapy device is disclosed. The method comprises providing a probe having a surface, positioning the surface in a flux of a radionuclide, and collecting nuclei of the radionuclide on or beneath the surface. The surface is positioned and the nuclei are collected in a manner such that decay chain nuclei and alpha particles of the radionuclide are emitted outside the surface.