A filler material comprising an energy intercepting element. In an embodiment, an energy intercepting element may attenuate, redirect, concentrate, or otherwise modify the properties of intercepted energy, e.g. the incoming energy flux. In an embodiment an energy intercepting element may be changed, for example generating secondary electrons, and/or secondary radiation, by intercepted energy. Also disclosed is a method comprising introducing a filler material composition into a cavity within a tissue in a patient's body, wherein the filler material includes an energy intercepting element(s) for intercepting energy and directing an energy source at the filler material.