Abstract
Background:Pulmonary fibrosis (PF) occurs in the majority of patients with SSc and is a leading cause of SSc-related death. SSc related PF has heterogeneous disease progression: many patients will have a chronic, indolent course while others may develop the progressive, life-threatening disease.Objectives:The objective of this study is to investigate the discrimination performance of quantitative CT indexes in identifying the parenchymal differences between the SSc and the control groups. We also aimed to demonstrate the correlation among quantitative indexes (QI), spirometric pulmonary function tests, and visual CT scores in patients with PF.Methods:A total of 135 SSc patients (female 87.4%; age, 50±13 years), 41 of whom had pulmonary fibrosis (PF), and 38 healthy subjects (female 89.5%; age, 52±6 years) were enrolled. All participants underwent volume thin-section CT in the supine position at full inspiration and spirometry. Quantitative indexes (QIs) were obtained using dedicated software for the segmentation of the lung (Vital Images Vitrea Workstation; Version 7.12.3.133). QIs included total lung volume (TLV), low attenuation (LA) volume (-1020 HU<pixel<-920 Hounsfield units [HU]), medium attenuation (MA) volume (-920 HU<pixel<-920 HU), and high attenuation (HA) volume (-720<pixel<0 HU). The global extent of pulmonary parenchymal abnormality was measured semiquantitatively by visual scoring (VS) and functional lung volume was derived. The functional lung volume, total MA volume, and ratio of total MA to total lung volume were assumed as the indexes of normal lung parenchyma.Results:MA volumes, HA volumes, total lung volumes and the ratio of MA volume to total lung volume differed significantly between the patients with PF, patients without PF, and the control group. In the PF group, FVC showed significant correlation with functional lung volume (r=0.45, p=0.014) and total MA volume (r=0.48, p=0.009); DLCO showed significant correlation with VS of normal lung parenchyma (r=0.65, p<0.001), functional lung volume (r=0.53, p=0.006), total MA volume (r=0.54, p=0.005) and ratio of total MA to total lung volume (r=0.42, p=0.031). The functioning lung volume obtained by VS and total MA volume showed excellent correlation (r=0.78, p<0.001).Conclusion:Quantitative indexes measured by soft-ware differentiated the patients with PF from the patients without PF and healthy subjects. The indexes used to evaluate the normal lung parenchyma showed a good correlation with pulmonary function test results. Quantitative indexes can be used as an objective complementary tool for the evaluation of the lung areas unaffected by PF.Table 1.Quantitative Indexes of CT in the Control, SSc without PF and SSc with PF GroupsControlSSc without PFSSc with PFpRight lung LA volume (ml)372±375420±446254±3080.102Right lung MA volume (ml)1230±4081377±441987±451<0.001Right lung HA volume (ml)531±152494±177625±2150.004Left lung LA volume (ml)342±370367±383221±2710.089Left lung MA volume (ml)1014±3831170±433805±402<0.001Left lung HA volume (ml)563±176516±251620±2890.037Total lung LA volume (ml)712±736827±959517±6530.119Total lung MA volume (ml)2212±8632548±8621756±850<0.001Total lung HA volume (ml)1072±3431009±4061290±5220.005Total lung volume (ml)3996±12374385±12563563±12360.002Mean lung density (HU)-799±61.4-798±63-730±75<0.001Total MA volume/Total lung volume0.55±0.120.59±0.130.49±0.150.002Figure 1.Segmentation of lung parenchymaDisclosure of Interests:None declared
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