Biological dosimetry and Relative Biological Effectiveness (RBE)

Biological methods of dosimetry are needed when absorbed dose alone is inadequate for correlation with biological effect. This occurs when RBE is unknown or variable and sometimes when irradiation is non-uniform. Biological dosimetry is particularly useful with high-LET radiations such as fast neutrons, heavy ions and PI- mesons. The RBE of fast neutrons depends on many factors. The effects of neutron energy, dose level and n/γ ratio are discussed. Methods of predicting the effect of mixed radiations (n+γ) are analysed in some detail and compared with an experimental result. Mammalian cells have been used as dosimeters to check the validity of physical measurements of dose distributions from beams of fast neutrons and charged particles. This method has its greatest value in the design of filters for velocity modulation of heavy-ion beams. Finally a few comments are made about the use of chromosome aberrations in human lymphocytes, a method which has been found of great value in the assessment of radiation accidents. (author)