Association of dual-energy CT-derived quantitative parameters with hydroxyproline levels and pulmonary function in nonspecific interstitial pneumonia.

BACKGROUND: This study evaluated the feasibility of dual-energy CT (DECT) for assessing the correlation between hydroxyproline (HYP) levels in lung tissue of patients with nonspecific interstitial pneumonia (NSIP) and lung volume and pulmonary function. METHODS: We retrospectively analyzed 99 NSIP patients (51 cellular, 48 fibrotic) and 40 controls. All underwent DECT imaging. Lung HYP‑equivalent density (HYP‑ED) and volume were quantified using spectral post-processing. Pulmonary function parameters, including FVC% Pred and DLCO% Pred, were collected. Intergroup differences, correlations, and diagnostic performance were assessed. RESULTS: Lung volume was higher in controls (3797.40 ± 1155.68 cc) than in cellular (2796.88 ± 334.03 cc) and fibrotic NSIP (2156.76 ± 423.40 cc; P < 0.001). HYP‑ED was lower in controls (206.29 ± 22.40 mg/cm3) than in cellular (264.31 ± 24.99 mg/cm3) and fibrotic NSIP (327.12 ± 36.26 mg/cm3; P < 0.001), and lower in cellular than fibrotic NSIP (P < 0.001). FVC% Pred and DLCO% Pred were higher in cellular NSIP (75.98 ± 4.07% and 69.96 ± 4.41%) than in fibrotic NSIP (71.44 ± 5.49% and 64.58 ± 3.38%; P < 0.05). HYP‑ED content showed significant negative correlations with lung volume and pulmonary function (all P < 0.01). HYP‑ED demonstrated excellent diagnostic performance for distinguishing NSIP subtypes (AUC 0.977), with 91.8% sensitivity and 92.9% specificity. CONCLUSIONS: DECT enables noninvasive quantification of lung HYP-ED in NSIP. HYP‑ED correlates with disease severity and may serve as a promising imaging biomarker for fibrosis assessment and monitoring.