ICRU Report No. 45 is the first of two reports addressed to clinical neutron dosimetry. The report focuses on standardization of the dosimetry procedures used in support of the clinical applications of fast neutrons. It has been recognized that the comparison of the clinical results of fast neutron therapy at different institutions is compromised by difficulties in comparing the technical irradiation conditions.
This is true even though institutions use the methods for determining the absorbed dose and kerma of fast neutrons recommended in ICRU Report 26, Neutron Dosimetry for Biology and Medicine. As a result, ICRU Report 45 provides guidance on the values of parameters and experimental techniques to be employed with the aim of standardization of the dosimetry procedures. Since radiation quality is important, a major section of the report treats experimental methodology and results of energy spectrum measurements of clinical neutron beams that yield information necessary for the characterization of the radiation quality. This is followed by a review of the dosimetric methods available for clinical neutron dosimetry. Beam characteristics are treated next, with coverage of such matters as output, dose build-up, depth dose and penumbra. A treatment of experimental and theoretical methods for determination of absorbed dose distributions concludes the report. Biological problems, such as the dependence of relative biological effectiveness on the neutron energy spectrum and the relative contribution of gamma rays to the absorbed dose, are to be treated in the second report of the series.