Abstract: The objective was to investigate the pattern of evolution of severe acute respiratory syndrome(SARS)on Chest radiographs.Chest radiographs of 54 SARS patients were analyzed retrospectively.Pulmorary lesions in different location,shape,number,area and density were observed in different period of time.Initial chest radiographs showed unilateral involvement(33 of 54 cases,6 cases of them evolved to bilateral involvement on the following chest radiographs)and bilateral involvement(21cases).Lower lung field(64.82%)and middle lung zone(94.44%)were more commonly involved.The evolution of shape of lesions included three patterns,the pattern of patchy opacities-shaggy cloudy shadow-increase of focal interstitial markings-absolutely absorption was found in most patients(64.82%).The evolution of number of lesions included five patterns,among which unifocal involvement(40.74%)was the most common pattern.Three patterns of evolution of lesion area were recognized:one-peak pattern(79.63%),two-peak pattern(12.96%)and progressive deterioration pattern(7.41%).The evolution of lesion density included four patterns:one-peak pattern(57.69%),two-peak pattern(29.49%),three-peak pattern(7.69%)and progressive deterioration(5.13%)pattern.Significant difference was found in disease course and the largest lesion proportion to the whole lung in different types of evolution.Conclusion To some extent,the radiographic evolution of SARS is regular and the radiographic evolution can suggest the prognosis of SARS patients.

Key words: SARS, chest radiographs, pneumonia