| PrefaceSmall airway diseases are common respiratory diseases which mainly involved the airways 3mm or less in diameter, the vast of them represent bronchioles. Abnormalities of the small airways may originate within these airways themselves or result from extension of diseases involving either the larger bronchi or the lung parenchyma. HRCT can completely demonstrate the subtle structure and the abnormal changes or signs of small airways and provide the morphologic bases for diagnosing small airway diseases, HRCT is currently the best imaging technique for assessment of small airway diseases, it s a common sign is Mosaic attenuation that dont only objectively reflect the site, range and extent of small airway diseases but also proximately estimate the functional abnormalities. In this study, we collected 50 patients who have Mosaic attenuation on HRCT of lung, 32 of them performed expiratory CT scans. By measuring the extent of Mosaic attenuation on HRCT and low attenuation on expiratory CT scans and correlate them with the results of pulmonary function test (PFTs) , we want to discuss its correlation and evaluate the clinical significance.Materials and methodsThe study collected 50 cases who have Mosaic attenuation on HRCT scans of lung , 10 cases as normal contrast group. All cases were examined with thin - section spiral CT, scanned from the apex to right diaphragm top in one breathing hold during stationary breathing. Speed 0. 5s/round, data collection thickness 0. 5mm, reconstruction thickness 1.0mm, interval 10mm and all scans were reconstructed with a high spatial frequency algorithm, Subjective analysis of the findings was performed at WW:1500HU, WL: -800HU for observing the airway and lung parenchyma. In 32 of 50 cases, end - expiratory scans were obtained at three selected levels; the aortic arch, the cari-na, 5.0cm below the carina.CT scans were reviewed independently by two chest radiologist for determining the presence of Mosaic attenuation on HRCT, and their extent, three semiquantitative scores were obtained , they are Mosaic score , low attenuation score and low attenuation score on expiratory scans. In all cases, pulmonary function tests were performed within the same week that the HRCT were obtained , the relative parameters were recorded as follow: forced expiratory volume at one second (FEV,) , forced expiratory flow at 25% VCCFEF25% ) , forced expiratory flow at 50% VC ( FEF50% ) , forced expiratory flow at 75% VC ( FEF75% ) , forced expiratory flow at 25 - 75% VC ( FEF25-75%). In-terobserver agreement on semiquantitative scores was assessed using kappa statistic, the correlation of semiquantitative scores with each PFTs were evaluated by nonparametric test (Spearman rank correla-r tion).ResultsIn 50 patients, the mean of Mosaic score was 6.74+4.15 ( range 1 -20) , the mean of low attenuation score was 4. 24 +2. 32(range 1 -11) , the mean of low attenuation score on expiratory scans was 8. 41+3. 96(range 2 - 16), the mean of FEV, was 77. 04%+ 18. 69 (range 35% - 125% ) , the mean of FEV25% was 61. 12% + 20. 80 (range 21% - 130% ) , the mean of FEV50% was 64. 4% + 26. 91 (range 19% - 131%) the mean of FEV75% was 59. 76% +23. 82 (range 14% - 132% ) , the mean of FEV25-75% was 63. 98% +24. 21 ( range 21% - 132% ) . the correlation of Mosaic score, low attenuation score, low attenuation scoreon expiratory scans with each PFTs are respectively by nonparametric test ( Spearman rank correlation) , we found the coefficients of these scores with FEF25% are better than others (rs= -0.4675, -0.6125, -0.7211, respectively ,all p<0. 001).Discussion1. HRCT findings of small airway diseases and the pathgenesis of mosaic attenuationsmall airway diseases are a series of commonly chronic respiratory diseases that mainly involved the airway which diameter is 3mm or less than 3mm, the vast majority of which represent brochioles. Abnormalities of the small airway may originate within these airways themselves or result from extension of diseases involving either the lar...
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