POS0892 QUANTITATIVE CT INDEXES: PROMISING TOOLS FOR OBJECTIVE ASSESSMENT OF PULMONARY FIBROSIS IN SYSTEMIC SCLEROSIS
Authors: D. Temiz Karadağ, O. Cakir, S. Şan, A. Yazici, A. Cefle
Journal: Annals of the Rheumatic Diseases (2021)

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&lt;pixel&lt;-920 Hounsfield units [HU]), medium attenuation (MA) volume (-920 HU&lt;pixel&lt;-920 HU), and high attenuation (HA) volume (-720&lt;pixel&lt;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&lt;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&lt;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 Groups Control SSc without PF SSc with PF p Right lung LA volume (ml) 372±375 420±446 254±308 0.102 Right lung MA volume (ml) 1230±408 1377±441 987±451 &lt;0.001 Right lung HA volume (ml) 531±152 494±177 625±215 0.004 Left lung LA volume (ml) 342±370 367±383 221±271 0.089 Left lung MA volume (ml) 1014±383 1170±433 805±402 &lt;0.001 Left lung HA volume (ml) 563±176 516±251 620±289 0.037 Total lung LA volume (ml) 712±736 827±959 517±653 0.119 Total lung MA volume (ml) 2212±863 2548±862 1756±850 &lt;0.001 Total lung HA volume (ml) 1072±343 1009±406 1290±522 0.005 Total lung volume (ml) 3996±1237 4385±1256 3563±1236 0.002 Mean lung density (HU) -799±61.4 -798±63 -730±75 &lt;0.001 Total MA volume/Total lung volume 0.55±0.12 0.59±0.13 0.49±0.15 0.002 Figure 1. Segmentation of lung parenchyma Disclosure of Interests: None declared