Radionuclides and bone - from 226Ra to 90Sr

Consideration is given to the toxicity of 226Ra and 90Sr and to the need for dosimetry that is relevant to the possibility of tumour induction by these radionuclides. The tissue at risk from bone seekers are identified and new methods are given of determining the absorbed dose in bone marrow and endosteal tissues. The calculations of energy deposition are based on measured distributions of path lengths through trabeculae and marrow spaces and are thus linked directly to the structure of individual bones. Results are given for various β emitters and for 226Ra α particles in both human and animal bone; they are considered in relation to radiobiology, radiation protection and the dose to infant bone from fall-out 90Sr. It is shown that bone structure affects the magnitude of the dose from any incorporated radionuclide and that differences in structure must be taken into account in translating the results of toxicity studies in animals to man.