Respiratory function data are useful for the evaluation of lung disease. To develop a new method of computer analysis for screening chest radiography that would provide respiratory kinetics automatically, we quantified and analyzed the movement of pulmonary markings and the changes in lung density during respiration. In this study, we obtained fluoroscopic chest images of a healthy volunteer during respiration using an image intensifier(I. I.) fluoroscopy system. We analyzed the vector of the movement of pulmonary markings and measured the regional mean density of sequential chest images during respiration. The movement of pulmonary markings in the upper lung field was less than that in the lower lung field. Variation in the phase density curve of the upper lung field was less than that of the lower lung field. Our results indicate that changes in density were regular and were synchronized with respiration. This computerized method may aid radiologists in the evaluation of lung diseases such as chronic obstructive pulmonary disease (COPD), where abnormal respiratory change in density occurs as a result of air trapping.
