[Use of the micronucleus test for biological dosimetry in cases of homogeneous or non-homogeneous exposure to ionizing radiations].

The dose effect relationship after homogeneous irradiation and the effect on the Poisson distribution of adding non-irradiated blood and thereby simulating non homogenous accidental exposure were studied for dicentric aberrations and micronuclei in lymphocytes exposed in vitro to 60Co gamma irradiation. The dose effect relationship for both parameters was of the linear quadratic type with the micronuclei responding slightly less to radiation than the dicentrics but a greater number of cells can easily be screened for micronuclei than for dicentrics. Except for one dose level in micronuclei, no deviations from the Poisson distribution were observed, after homogeneous tradition, but such a deviation was evident when non-irradiated blood was added to the irradiated one. With the help of the method of the "contaminated Poisson distribution" the proportion as well as the dose of the exposed blood could be approximately estimated. In order to test the suitability of the micronucleus test in vivo, both dicentrics and micronuclei were determined in patients treated for seminoma to an abdominal field. The data showed a consistent increase in both parameters without a significant difference between patients. The increase of both types of anomalies corresponded about to that expected from the size of the field exposed. The data from micronuclei appear, therefore, about as reliable for biological dosimetry as those from dicentrics for biological dosimetry after homogeneous and non-homogeneous exposure to ionizing radiations.