胸部摄影自动曝光控制装置影像密度与焦-片距的相关性研究

目的:探讨胸部摄影AEC自动曝光控制下影像密度与焦-片距的相关性。方法:利用胸部摄影自动曝光控制装置,使用不同的焦-片距离,摄取正常的标准胸片24张,确定7个评价测试点,用密度计分别测量7个测试点的密度值。结果:肺野的密度与焦-片距离没有密切的相关性(r<0.811P>0.05只有气管分叉处的密度值与焦-片距之间有非常显著的负相关(r=-0.955P<0.01)。结论:考虑病人的吸收剂量和避免影像失真,摄影焦-片距的选择应与滤线栅的焦距相匹配。

A STUDY ON THE CORRELATION OF IMAGE DENSITY WITH FOCUS-FILM DISTANCE IN AUTOMATIC EXPOSURE CONTROL OF CHEST RADIOGRAPHY

Objective: To investigate the correlation of image density with focus-film distance in automatic exposure control(AEC) of chest radiography. Method: Taking the focus-film distance as a single varian, the 24 chest radiographs in various focus-film distance were selected according to AEC standard and we confirmed 7 evaluation points were selected and the density of each evaluation point were measured by densitometer. Results: It showed that the density of lung field was not closely correlated with the focus-film distance (all r<0.811, all P >0.05) except at the area of trachea branch (r<-0.955,P <0.01). Conclusion: Considering the absorbed dose of the patients and avoiding the image distortion, It is suggested that the selection of focus-film distance should be matched with the tube and grid.