Standardised 3D-CT lung volumes for patients with idiopathic pulmonary fibrosis

Abstract

Background: The assessment of lung physiology via pulmonary function tests (PFTs) is essential for patients with idiopathic pulmonary fibrosis (IPF). However, PFTs require active participation, which can be challenging for patients with severe respiratory failure, such as during moments of acute exacerbation (AE) of IPF. Recent advances have enabled the re-construction of 3-dimensional computed-tomography (3D-CT) images. This study established a standardisation method and quantitative analysis of lung volume (LV) based on anthropometry using 3D-CT images. Methods: This is a retrospective multi-center cohort study. The standardised 3D-CT LV in patients with IPF at diagnosis (n = 140) and during AE (cohort1; n = 61 and cohort2; n = 50) and those of controls (n = 53) were assessed. Results: The standardised 3D-CT LVs at IPF diagnosis were less than those of control patients, especially in the lower lung lobes. The standardised 3D-CT LVs were correlated with forced vital capacity (FVC) and validated using the modified Gender-Age-Physiology (GAP) index. The standardised 3D-CT LVs at IPF diagnosis were independently associated with prognosis. During AE, PFTs were difficult to perform, 3D-CT analyses revealed reduced lung capacity in both the upper and lower lobes compared to those obtained at diagnosis. Lower standardised 3D-CT LVs during AE were independently associated with worse outcomes in the two independent cohorts. In particular, volume loss in the upper lobe at AE had prognostic values. Conclusions: A novel image quantification method for assessing pulmonary physiology using standardised 3D-CT-derived LVs was developed. This method successfully predicts mortality in patients with IPF and AE of IPF, and may be a useful alternative when PFTs cannot be performed.