Threshold-based quantitative CT lung volumes and clinical outcomes in idiopathic pulmonary fibrosis

Abstract

The primary objective of our study was to evaluate the correlation between threshold-based quantitative lung volumetric measurements obtained from thoracic computed tomography (CT) scans and clinical data in patients with idiopathic pulmonary fibrosis (IPF), and to demonstrate their impact on prognosis and mortality. Patients who underwent non-contrast thoracic CT at Ankara Bilkent City Hospital between January 2019 and December 2024 and exhibited a usual interstitial pneumonia pattern in the lung parenchyma were retrospectively screened. IPF patients meeting the inclusion criteria were enrolled, along with an equal number of age- and sex-matched control subjects without any chronic lung disease. Quantitative measurements of normally aerated lung volumes and fibrotic lung volumes were performed using the Thoracic VCAR (GE Healthcare) software, an artificial intelligence-based analysis package installed on a dedicated workstation. To ensure technical precision, all automated segmentations were manually reviewed by two experienced radiologists (intraclass correlation coefficient ≥ 0.90). All CT measurements were compared between the patient and control groups. Quantitative lung volume measurements of the patient group – including normally attenuated lung volume (NALV [l, %]), low-attenuation lung volume (LALV [%]), high-attenuation lung volume (HALV [l, %]), and total lung volume – were significantly lower than those of the control group (p < 0.05). The mean total lung volume in the gender-age-physiology (GAP) index, GAP stage 1 group was higher than that in the GAP stage 2 and 3 groups. Significant differences were observed in NALV (l, %), HALV (l, %), and total lung volume measurements between patients who desaturated and those who did not during the 6-minute walk test (p < 0.05). Significant positive correlations were found between total lung volume and forced vital capacity (l), forced expiratory volume in 1 second (l), vital capacity (l), and total lung capacity (l) (p < 0.05). Univariate Cox regression analysis revealed that NALV (%) was significantly associated with all-cause mortality, independent of other factors. NALV (%) obtained through quantitative CT analysis may be a useful prognostic biomarker for predicting two-year mortality in IPF patients. This objective, effort-independent imaging biomarker may provide a valuable alternative for prognostic assessment, particularly in patients who exhibit limited ability to perform functional tests.