Implications of dosimetry intercomparisons for standardization in neutron dosimetry for biological and medical applications

Neutron dosimetry intercomparisons are of great importance for adequate evaluation and comparison of biological and clinical results obtained at different research centres. The variations in the results obtained by participants in two international neutron dosimetry intercomparisons (INDI and ENDIP) for neutron and total kerma or absorbed dose are of the order of 7% to 8%. These variations seem to be in accordance with the relatively large systematic uncertainties quoted, which are attributed to insufficient knowledge of basic physical parameters. In order to determine the influence of the use of different values for the physical parameters such as anti W, kerma ratios and stopping power ratios, the responses of participants' dose meters were also compared. The variances of quoted kerma and absorbed dose values are of the same order of magnitude as those of instrument responses. This result implies that there are large systematic differences in measurement procedures applied by the different participants. Although adoption of uniform basic parameters is desirable, it seems more important to standardize the experimental techniques employed for the determination of absorbed dose. Within the framework of a CEC sponsored programme of CENDOS (collection and evaluation of neutron dosimetry data) a study of possible operational errors is being performed for a number of participants whose results showed large differences. The purpose of this special intercomparison is to solve existing discrepancies, to learn about detector characteristics and to decide on the appropriateness of different types of ionization chambers to be used as reference dose meters. (author)