Quantification of MRI T2 Interstitial Lung Disease Signal-Intensity Volume in Idiopathic Pulmonary Fibrosis: A Pilot Study

Abstract

Background: Imaging has played a pivotal role in the diagnosis of idiopathic pulmonary fibrosis (IPF). Recent reports suggest that T₂ -weighted MRI could be sensitive to monitor signal-intensity modifications of the lung parenchyma, which may relate to the disease activity in IPF. However, there is a lack of automated tools to reproducibly quantify the extent of the disease, especially using MRI.

Purpose: To assess the feasibility of T₂ interstitial lung disease signal-intensity volume quantification using a semiautomated method in IPF.

Study type: Single center, retrospective.

Population: A total of 21 adult IPF patients and four control subjects without lung interstitial abnormalities.

Field strength/sequence: Both free-breathing ultrashort echo time (TE) lung MRI using the spiral volume interpolated breath hold examination (VIBE) sequence (3D-UTE) and T₂ -BLADE at 1.5T.

Assessment: Semiautomated segmentation of the lung volume was done using 3D-UTE and registered to the T₂ -BLADE images. The interstitial lung disease signal-intensity volume (ISIV) was quantified using a Gaussian mixture model clustering and then normalized to the lung volume to calculate T₂ -ISIV. The composite physiological index (CPI) and forced vital capacity (FVC) were measured as known biomarkers of IPF severity. Measurements were performed independently by three readers and averaged. The reproducibility between measurements was also assessed.

Statistical tests: Reproducibility was assessed using the intraclass correlation coefficient (ICC) and Bland-Altman analysis. Correlations were assessed using Spearman test. Comparison of median was assessed using the Mann-Whitney test.

Results: The reproducibility of T₂ -ISIV was high, with ICCs = 0.99. Using Bland-Altman analysis, the mean differences were found between -0.8 to 0.1. T₂ -ISIV significantly correlated with CPI and FVC (rho = 0.48 and 0.50, respectively; P < 0.05). T₂ -ISIV was significantly higher in IPF than in controls (P < 0.05).

Data conclusion: T₂ -ISIV appears to be able to reproducibly assess the volumetric extent of abnormal interstitial lung signal-intensity modifications in patients with IPF, and correlate with disease severity.

Level of evidence: 4 TECHNICAL EFFICACY STAGE: 1.

Keywords: MRI; idiopathic pulmonary fibrosis; interstitial disease; lung.