THE CLINICAL RBE AND MICRODOSIMETRIC CHARACTERIZATION OF RADIATION QUALITY IN FAST-NEUTRON THERAPY

High-LET radiation therapy using fast neutrons is being applied regula rly at several centres worldwide and in the future, other types of rad iation qualities, such as protons and heavier ions and boron neutron c apture therapy (BNCT) are likely to be used. The neutron beams used ar e of considerably varying energy and thus considerable variations in t he relative biological effectiveness (RBE) have been found. At present , no generally accepted method exists for the quantitative specificati on of these differences in radiation quality for clinical purposes. Th is is in clear discrepancy with the accuracy requirements in clinical dosimetry. An approach is presented which is based on a single paramet er radiation quality characterization determined in combined microdosi metric and radiobiological experiments. It is shown that the method ca n meet the accuracy requirements of clinical dosimetry and that it is applicable within a concept of formalized procedure of clinical practi ce and experience ('clinical RBE').