ABSTRACT
Objective To investigate the changing curve of mean lung density (MLD)in normal preschool children based on CT quantitative measurement.Methods Chest CT data of 409 preschool children were reviewed retrospectively from the "digital lung"database.A computerized algorithm based on the "digital lung"was applied to all examinations in a batch manner.The MLD values of total lung,right lung,left lung and each lobe were obtained automatically.Results There was no correlation between the gender and MLD,however a moderately negative correlation was found between the age of month and MLD (P＜0.05).No significant difference of MLD was found between genders of the same age of month group,except in left lower lobe of 49-60 months of age (P=0.043). The MLD was decreased gradually with age (P＜0.05).Conclusion There is not a statistical difference in MLD between the preschool boys and preschool girls of the same age of month.With the growth of preschool children,the MLD is gradually decreased.