| It is critical to know and determine radiation dose when the acute and chronic victims exposed to radiation accident were classed, diagnosed and treated during dealing with radiation accident. Although present physics dosimetry both in veracity and reliability can meet the need on measurement of professional radiation dose of individual and work environment, it doesn't work well in special condition, such as biogenesis radiation accident, large scale study of radiation damage in crowd, and losing physics dosimetry etc. Therefore, it is very important to study a reliable biological measurement to estimate radiation dose and to evaluate late effect of cytogenetics. Up to now, cytogenetics technology is used as most of biological dosimetry. In this study, biological doses were estimated by using the yields of dicentrics plus rings (dic+r) and cytokinesis-block micronuclei (CBMN) in some victims exposed toaccident radiation, and late effect of cytogenetics was studied in the victims.Part one: Biological dose assessment by the analyses of chromosomal aberrations and CB micronuclei in 9 cases exposed to radiation accidentMethods: Biological dose assessment was performed by the analyses of chromosomal aberration and CB micronuclei for 7 victims ("A", "B", "C", "D", "E", "F" "G") in Xinxiang, one victim ("H") in Xuchang and one victim('T') in Kaifeng exposed accidentally to gamma-rays in Henan province. The individual radiation dose was estimated by the yields of dicentrics plus rings(dic+r) and CBMN. The well-distributed exposure or non-uniform one was tested by the Poisson distribution of dic+r. The slide preparation of chromosome and CBMN was performed by using the routine culture, and the cyt-B was added to the culture medium(a final concentration of 6 mg/L) after 44 hr-incubation at 37℃.Results:1. The equvalent whole body doses based on the standard dose-response curves established by the analyses of dic+r were estimated to be 5.09Gy(A), 2.61Gy(B), 2.49Gy(C), 0.89Gy(D), 0.70Gy(E), 0.58Gy(F), 0.08Gy(G), 1.41Gy(H)and 0.15Gy(I). These doses were very consistentwith the mean doses calculated from physical measurement and conformable to the clinical diagnosis.2. Using cytokinesis-block micronuclei(CBMN), the equivalent whole body doses for the 5 victims were estimated to be 0.97Gy(D), 0.74Gy(E), 0.58Gy(F), 1.43Gy(H)and 0.22Gy(I). These doses were were very consistent with the doses calculated by using the yields of dicentrics plus rings(dic+r) and conformable to the clinical diagnosis of 5 victims.Conclusion:1. The analysis of chromosomal aberrations is an extremely reliable in biological dosimetry. The radiations which "A", "C", and "H" were exposed to were heterogeneous while they were homogeneous for the other 6 victims.2. CBMN analysis is also an extremely reliable in biological dosimetry. Culturing sample and checking micronuclei were done as soon as radiation accident occurred. The best is within 7 days after accident occurred.Part two: Late Observation of Cytogenetics in victims exposed to 60Co Radiation AccidentMethods: Culture of lymphocyte, and slide preparation of chromosome and CBMN were the same as that of first part.Results:l.The following results of chromosomal aberrations and CBMN in 6 victims exposed to 60Co radiation accident in Xinxiang after 1-2 years. Frequencies of chromosomal aberrations and CBMN obviously decrease in the 6 victims. The Dic+r aberrations remained main proportion in 1 year after irradiation and evidently decreased after 2 years. 2. The analyses of chromosomal aberrations and micronuclei were performed in 3 victims exposed to ^Co radiation accidnet in 6(7) years and 16(17) years after irradiation. Results showed that the frequencies of chromosomal aberrations in exposed victims were 4.29% in 6(7) years and 3.63% in 16(17) years after irradiation, respectively, and the difference was not significant in the two times follow-up study. Most of the chromosomal aberrations were acentric and dicentric chromosomes in first time follow-up study, and translocation, deletion and inversion chromosomes in second time follow-up one. The frequencies of micronuclei in exposed group were 4.17%o and 1.17%o in the two times follow-up study, respectively, and the rates of micronuclei in second time follow-up study were much lower than that in first one.Conclusion:1. The unstable type aberrations were gradually lost as time goes on, and the level of stable type aberration was of high degree.2. The analyses of stable chromosome aberrations is a important index to evaluate late effect of cytogenetics in radiation accident.
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