By application of the conditional Logistic regression model, the factors influencing iron deficiency anemia in preschool children from 3 to under 7 years old have been analysed. To estimate the mode parameters, Newton-Raphson iterative method has been used. By 81 matched groups of 1:4 paired case-control and among seventeen hazard factors, five significant factors contained in the model are as follows: eating less meat, fewer vegetables and fruits, having a poor appetite and cooking with aluminium utensils.

Objective To explore the relationship between image quality and different exposure intensity of digital radiography(DR).Methods Using a contrast-detail phantom Cdrad 2.0,observers evaluated images on the monitots when exposure parameters were 90 kV and mAs ranged from 0.5 to 16.0 mAs.Then calculate image quality figure(IQF),and ANOVA was used to analyze the difference of IQF under different radiation dose in 8 subjects.Results (1)When exposure parameters were 90 kV and mAs altered from 0.5 to 8.0 mAs.the IQF observed on the monitor was reduced,and the minimal value was 38.54±2.82.When mAs changing from 8.0 to 16.0 mAs.IQF observed on the monitor was increased,and the maximum was 44.33±2.35.(2)Under the different exposure condition,the difference of IQF values were statistically significant(F=60.35,P＜0.01).Conclusions With the increased exposure intensity,the image quality on monitor increased.When mAs was 8.0 mAs,image quality was the optimum When mAs was more than 8.0 mAs,the image quality on monitor reduced.