Quantitative CT assessment of pulmonary vascular structural changes in connective tissue disease patients without interstitial lung abnormalities

Background and objective To investigate changes in pulmonary vascular quantity and structure in patients with connective tissue disease (CTD) who have no interstitial lung abnormalities, to characterize quantitative pulmonary vascular differences in CTD without radiological ILD. Methods This study included CTD patients who underwent chest high-resolution CT (HRCT) at our institution between January 2013 and June 2025. Radiologists excluded those with interstitial lung abnormalities, resulting in a cohort of CTD patients without interstitial lung disease (CTD-nonILD). Artificial intelligence–based quantitative CT software (AVIEW) was used to assess vascular parameters, including total vessel number (Ntotal), number of small vessels (<5 mm 2 , NCSA5), mean vessel diameter (VDmean), total vessel area (VAtotal), total lung blood volume (TBV), and blood volume of small vessels (BV5)—at 6, 9, 12, 15, and 18 mm from the pleura in the whole lung and individual lobes. Parameters were compared with healthy controls. Results At the whole-lung level, N total was significantly higher in CTD-nonILD patients at 6 mm and 9 mm depths (P < 0.05), with no significant differences at deeper zones (P > 0.05). VD mean , BV 5 , and BV 5 /TBV were significantly elevated in both whole lung and all lobes (P < 0.05). NCSA5 increased markedly at 6 mm depth but decreased at 12, 15, and 18 mm (P < 0.05). In upper lobes, N CSA5 was significantly higher at 6 mm (P < 0.05); no significant difference was seen in lower lobes (P > 0.05). Conclusion CTD patients exhibit early pulmonary microvascular remodeling, characterized by peripheral proliferation of small vessels accompanied by relative small-vessel reduction in deeper parenchymal zones in CTD patients without radiological interstitial lung disease.