Pulmonary vessel volume in idiopathic pulmonary fibrosis compared with healthy controls aged > 50 years

Abstract

Idiopathic pulmonary fibrosis (IPF) is characterised by progressive fibrosing interstitial pneumonia with an associated irreversible decline in lung function and quality of life. IPF prevalence increases with age, appearing most frequently in patients aged > 50 years. Pulmonary vessel-like volume (PVV) has been found to be an independent predictor of mortality in IPF and other interstitial lung diseases, however its estimation can be impacted by artefacts associated with image segmentation methods and can be confounded by adjacent fibrosis. This study compares PVV in IPF patients (N = 21) with PVV from a healthy cohort aged > 50 years (N = 59). The analysis includes a connected graph-based approach that aims to minimise artefacts contributing to calculation of PVV. We show that despite a relatively low extent of fibrosis in the IPF cohort (20% of the lung volume), PVV is 2-3 times higher than in controls. This suggests that a standardised method to calculate PVV that accounts for tree connectivity could provide a promising tool to provide early diagnostic or prognostic information in IPF patients and other interstitial lung disease.

Figure 1

The impact of filtering segmentation artefacts on the estimation of pulmonary vessel-like volume (PVV) for IPF (baseline and follow-up data pooled) and controls. The four bar charts show PVV estimates for unfiltered and graph-based methods in controls and IPF. Graph-based PVV was lower in both IPF and controls. Statistically significant differences in volumes between the two cohorts were seen for both methods.

Figure 2

The impact of filtering segmentation artefacts on the estimation of pulmonary vessel-like (PVV) subvolumes for IPF. The bars indicate the percentage of PVV that is PVV10 + (dotted hatch), PVV10 (slashed hatch), and PVV5 (grey hatch). Numerical labels indicate the absolute values (mL) of each volume compartment. PVV5: volume of vessels with cross-sectional area less than 5 mm²; PVV10: volume of vessels with cross-sectional area 5–10 mm²; PVV10 + : volume of vessels with cross-sectional area > 10 mm².

Figure 3

Comparison of the distribution of sub-volumes as a proportion of estimated pulmonary vessel-like volume (PVV) for IPF and controls. The stacked bars indicate the percentage of PVV that is PVV10 + (dotted hatch), PVV10 (slashed hatch), and PVV5 (grey hatch). Numerical labels indicate the absolute volumes (mL) of each volume compartment. PVV5: volume of vessels with cross-sectional area less than 5 mm²; PVV10: volume of vessels with cross-sectional area 5–10 mm²; PVV10 + : volume of vessels with cross-sectional area > 10 mm².

Figure 4

Relationships between estimated pulmonary vessel-like volume (PVV) and fibrosis as a percentage of imaged lung volume for IPF (grey) and controls (black). P value for IPF: p < 0.001 and controls: p = 0.04. PVV5: volume of vessels with cross-sectional area less than 5 mm²; PVV10: volume of vessels with cross-sectional area 5–10 mm²; PVV10 + : volume of vessels with cross-sectional area > 10 mm².

Figure 5

Relationships between estimated pulmonary vessel-like volume (PVV) and percent predicted diffusion capacity for carbon monoxide (D_LCO%) for IPF (grey) and controls (black). Control PVV has a positive relationship, and IPF a negative relationship, with D_LCO%.