title: Comments on the 60Co graphite/air stopping-power ratio used in the AAPM TG21 protocol.
mesh_terms: D002244:Carbon; D003037:Cobalt Radioisotopes; D006108:Graphite; D006801:Humans; D011874:Radiometry / Q000295:instrumentation*
chemical_list: D003037:Cobalt Radioisotopes; D002244:Carbon; D006108:Graphite