Idiopathic Pulmonary Fibrosis: Correlation Between Thin-section MSCT Findings And Pulmonary Function Test Results

Objective: To determine the correlation between thin-section MSCT findings and pulmonary function test results from patients with idiopathic pulmonary fibrosis (IPF).Methods: 30 cases with clinical and/or pathologically proved idiopathic pulmonary fibrosis. There were 15 man and 15 women aged 35⁷0 years (mean age 56.6±9.1). All patients underwent thin-section MSCT and HRCT scan was performed in 16 of them. Pulmonary function test for each patients was performed at the same day of CT scan. Thin-section MSCT scans were assessed for the presence and anatomic distribution of ground-glass attenuation (including air-space consolidation), reticular structures (including lobular septal thickening, intralobular septal thickening, bronchovascular bundles accentuated, subpleural lines), honeycombing, emphysema, traction bronchiectasis and pleural thickening. Then the extent of abnormal parenchyma was scored at six pre-selected levels: apex of lung (origins of great vessels), aortic arch, tracheal carina, hilum of lung, right inferior pulmonary vein, 1cm above the dome of the right hemidiaphragm. The values of pulmonary function tests included: vital capacity (VC), total lung capacity (TLC), residual volume (RV), ratio of residual volume to total lung capacity (RV/TLC), forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory volume in one second /forced vital capacity (FEV1), diffusion capacity for carbon monoxide of lung (DLCO), DLCO co rrected for alveolar volume (DLCO/VA), partial pressure of oxygen in arterial blood (PaO₂), partial pressure of carbon dioxide in arterial blood (PaCO₂), alveolar-arterial oxygen difference (P(A-a)O₂), et al. The correlation between thin-section MSCT score and the values of pulmonary function tests was examined using the Spearman rank correlation coefficient.Results: Of 30 cases, 24 had ground-glass attenuation (including air-space consolidation), 29 had lobular septal thickening, 26 had intralobular septal thickening, 28 had bronchovascular bundles accentuated, 4 had subpleural lines, 24 had honeycombing, 8 had emphysema, 22 had traction bronchiectasis, 14 had pleural thickening. The highest is lobular septal thickening (96.7%), the lowest is pleural thickening (14.2%). A predominant peripheral distribution was seen in lobular septal thickening (89.7%), intralobular septal thickening (84.6 % ), honeycombing (83.3 % ). A predominant peribronchovascular distribution was seen in bronchovascular bundles accentuated (92.9%). The pulmonary function tests of all patients revealed restrictive ventilatory defect. 15 of them were slight and the other 15 were moderate. All patients had diffuse function defect. 4 of them were slight, 14 were moderate, 12 were marked. There were 10 case with reduction of PaO2, 3 cases with elevation of PaCO2, 16 cases with elavation of P(A-a)O2. The total scores in thin-section CT of the slight restrictive ventilatory defect were 8¹4 (mean 11.00±1.89). The total scores in thin-section MSCT of the moderate restrictive ventilatory defect were 13²4 (mean 18.13±3.27). The total scores in thin-section MSCT of the slight diffuse function defect were 8¹0 (mean 9.25±0.96). The total scores in thin-section MSCT of the moderate diffuse function defect were 8¹8 (mean 12.36±2.34). The total scores in thin-section MSCT of the marked diffuse function defect were 14²4 (mean 18.92±3.00). The analytic results showed reticular structures negatively correlated with FVC (r=-0.623, p<0.001) and FEV1 (r=-0.472, p=0.009), honeycombing negtively correlated with FVC (r=-0.450, p=0.013), DLCO negatively correlated with reticular structures (r=-0.606, p<0.001) and honeycombing (r=-0.661, p<0.001), DLCO/VA negatively correlated with reticular structures (r=-0.385, p=0.036), honeycombing (r=-0.408, p<0.001) and traction bronchiectasis (r=-0.474, p=0.008), emphysema positively correlated with the staging of ventilatory defect (r=0.411, p=0.024) and diffuse function defect (r=0.400, p=0.029), traction bronchiectasis negatively correlated with DLCO (r=-0.392, p=0.032) and DLCO/VA (r=-0.474, p=0.008), positively correlated with the staging of diffuse function defect (r=0.466, p=0.009), air-space consolidation positively correlated with the staging of diffuse function defect (r=0.376, p=0.041), reticular structures negatively correlated with PaO2 (r=-0.430, p=0.018) and positively with P(A-a)O2 (r=0.416, p=0.022), The total scores in thin-section CT negatively correlated with VC (r=-0.646, p<0.001), TLC (r=-0.661, p<0.001), RV (r=-0.415, p=0.023), FVC (r=-0.624, p<0.001), FEV1 (r=-0.483, p=0.007), DLCO (r=-0.732, p<0.001), DLCO/VA (r=-0.504, p=0.005), positively correlated with the staging of ventilatory defect (r=0.843, p<0.001) and diffuse function defect (r=0.838, p<0.001).Conclusions: Thin-section MSCT can provide significant information for the assessment of the pathologic severity of idiopathic pulmonary fibrosis. Reticular structures and honeycombing correlate with the extent of fibrosis. Groud-glass attenuation correlated with the extent of alveolitis. There is good correlation between thin-section MSCT findings and pulmonary function tests results. Evaluation of thin-section MSCT signs conduces to predict the pulmonary function. Thin-section MSCT combined with pulmonary function tests can predict the progression , long term survival and response to therapy.