RESUMO
OBJECTIVE: To estimate the biological dose by the chromosome aberration analysis in a victim suffered in the radioactive source-loss accident in Nanjing City. METHODS: Peripheral blood sample of the victim was collected 6 days after radioactive exposure. Individual radioactive biological dose was estimated by identifying the aberration of the dicentrics plus centric rings in the metaphase chromosome of cells. The distribution of chromosome aberration was tested by the Poisson distribution. Impure Poisson distribution was used to estimate the radiation dose. RESULTS: Among the 353 cells observed at metaphase,75 aberration of dicentrics plus centric rings were found,43 cells had 1 aberration and 7 cells had 2 aberrations. Moreover,there were 3 multi-aberration cells with 3,4 and 11 aberrations respectively. The average individual radiation dose was estimated to be 1. 52 Gy,which was consistent with the clinical diagnosis as mild acute bone marrow radiation disease. The Poisson distribution u test revealed that the patient suffered from nonhomogeneous radiation.By the impure Poisson distribution test,the radiation exposure proportion of the whole body was estimated to be 55% and the average dose was 3. 02 Gy. CONCLUSION: The biological dose estimation was successfully performed,the results showed that this was a case of nonhomogeneous irradiation.
RESUMO
A survey of 420 exposures of mammography was performed with the parameters recorded. Entrance skin air kerma (ESAK) was measured and the mean glandular dose (MGD) was calculated according to the Dance's formula. Correlation analysis showed that several factors could affect the MGD level. Mann-whitney test and Non-parametric ANOVA analyses were used to compare the MGD level grouped by view type and radiographic systems. No significant difference was found in MGD between the craniocaudal (CC) group and the mediolateral oblique (MLO) group. The MGD level was higher in the CR group than in the other two groups. MGD was positively correlated with the compressed breast thickness (CBT). MGD varied with the half value layer (HVL) and increased first then decreased. The mean MGD level in China is about 1.6 mGy and is lower than the guidance level in the International Basic Safety Standards (IBSS).