[en] Experimental data on the neoplastic transformation of C3H 10T1/2 cells measured at Casaccia after neutron and X-ray irradiation were used to determine neutron RBE values for the RSV-Tapiro fast reactor energy spectrum and for monoenergetic neutrons of 0.5, 1, and 6 MeV. In parallel, micro-dosimetric measurements provided the actual lineal energy distributions and related mean parameters for the reactor radiation. From these experiments, values of the neutron quality factor were derived for the reactor neutron energy spectrum and, in turn, for the other neutron energies tested. A mathematical expression giving a smooth dependence on neutron energy was also determined for the effective quality factor in the entire energy range examined. The results were compared with other proposals

[en] A total of twenty groups from nine countries participated in sessions of the European Neutron Dosimetry Intercomparison Project (ENDIP) which were held during 1975 at GSF, Munich-Neuherberg and TNO, Rijswijk. The data of all participants are collected, the analysis and evaluation of the results are given in the present report. Specific chapters deal with the experimental arrangements and monitoring results at GSF and TNO, characteristics of the dosimetry systems employed by the paticipating groups and the basic physical data and correction factors employed for the determination of kerma and absorbed dose. In general, the participants in ENDIP quote systematic uncertainties of 7 to 8% in the neutron and total kerma or absorbed dose, which are mainly attributed to inadequate knowledge of basic constants. The variations in the results obtained by different participants seem to be in accordance with the relative large systematic uncertainties quoted. In order to determine the influence of the use of different values for the physical parameters, the relative responses of the participants' dosimeters have also been compared. The variances of quoted kerma and dose values are of the same order of magnitude as those of instrument responses. This result indicates inconsistencies in experimental techniques employed by the participants for the determination of kerma and absorbed dose. A separate nonparametric analysis of the ENDIP results confirmed that there are considerable systematic differences. Recommendations for future studies on neutron dosimetry for biological and medical applications are given at the end of the report

[en] This report describes the results of neutron and gamma mixed-field dosimetry obtained by the Ispra Group in the framework of the European Neutron Dosimetry intercomparison Project (ENDIP). The experimental method and the formulation employed for the derivation of Kerma results are also present

[en] Problems encountered in modelling radiation carcinogenesis are examined in the light of the available experimental information and discussed in view of existing attempts. The role of endogenous and exogenous factors is considered. (author)

[en] The general aims of the work are the study of the biological effectiveness of low radiation doses in vitro and in vivo, also in terms of interaction mechanisms. The shape of the dose-effect relationship at low doses of different radiation qualities was studied for various modes of irradiation, and, in particular, the influence of dose rate and radiation quality as well as of important biological host factors was considered, using appropriate experimental model systems, including neoplastic transformation of immortalized cell lines, and life-shortening and tumor induction in experimental animals. (R.P.) 10 refs., 1 fig

[en] Experimental data for neoplastic transformation of CrH 1OT1/2 cells measured at Casaccia after neutron and X-ray irradiation have been used to determine neutron RBE values for the RSV-Tapiro fast reactor energy spectrum and for monoenergetic neutrons of 0.5, 1, and 6 MeV. In parallel, microdosimetric measurements have provided the actual lineal energy distributions and related mean parameters for the reactor radiation. From these experiments, values of the neutron quality factor were derived for the reactor neutron energy spectrum and, in turn, for the other neutron energies tested. A mathematical expression giving a smooth dependence on neutron energy was also determined for the effective quality factor in the entire energy range examined, and the results have been compared with other proposals. (Author)

[en] In this review, low-dose levels for high- and low-LET radiation are defined to be <5 cGy and <20 cGy, respectively, and the data of various long-term mouse studies performed at Centro Casaccia's laboratories are considered especially on the analysis of the available results of the dose regions within 17 cGy for neutrons and 32 cGy for X-rays. Particularly, mouse studies are described on treatment with single doses of 1.5 MeV neutrons or 250-kVp X-rays, with fractionated or acute doses of fission neutrons, with in utero single doses of fission neutrons or 250-kVp X-rays and with single doses of fission neutrons in another mouse strain. In all cases the analysis object considered is the animal-at-risk and ovary and solid neoplasms are discussed. Data seem to reinforce the idea that at low doses the effectiveness of ionizing radiation is in practice very low in inducing neoplasms in the laboratory mouse. (K.H.)

[en] The production of chromosomal aberrations resulting from X irradiation of peripheral human blood lymphocytes in the presence or absence of Angioconray-80%, an iodised contrast medium, was investigated. This experiment confirmed an enhanced radiation effect, which is essentially explained by the increase of absorbed dose due to the high photoelectric cross section of iodine for X rays. Nevertheless the cytotoxicity of contrast medium alone cannot be neglected, and at a 0.1 M concentration in unirradiated blood it produced chromosome damage equivalent to 0.5 Gy. The distributions of aberrations among the cells, with and without contrast medium, were analysed using two statistical tests of goodness-of-fit for the Poissonian distribution. The results are discussed mostly in terms of dose enhancement factors. (author)

[en] Experimental studies, when carried out under well controlled experimental conditions and planned to investigate specific endpoints, can provide reliable information on many aspects of the biological action of radiation. In particular, animal studies are suitable to help in determining the shapes of the dose-response relationships for tumour induction, and the influence of dose rate, and in understanding the species and strain dependence, as well as the effect of factors such as sex, age and hormonal status. All these variables can diversely influence the biological response to radiations of different qualities, and thus the RBEs. These aspects are examined and discussed in the paper, special attention being addressed to the tumour induction to response of the haemolymphopoietic tissue and of epithetial tissues, such as liver and ovary, which have shown an appreciable degree of susceptibility to radiation carcinogenesis. (author)

[en] The influence of neutron collimation on the shape of energy deposition spectra was investigated using a spherical walled proportional counter. Experimental dose averaged lineal energies were obtained and compared with theoretical values. The fractions of total absorbed dose corresponding to various intervals of linear energies were also deduced from the measured distributions. (orig.)