Visual vs Fully Automatic Histogram-Based Assessment of Idiopathic Pulmonary Fibrosis (IPF) Progression Using Sequential Multidetector Computed Tomography (MDCT)

OBJECTIVES: To describe changes over time in extent of idiopathic pulmonary fibrosis (IPF) at multidetector computed tomography (MDCT) assessed by semi-quantitative visual scores (VSs) and fully automatic histogram-based quantitative evaluation and to test the relationship between these two methods of quantification. METHODS: Forty IPF patients (median age: 70 y, interquartile: 62-75 years; M:F, 33:7) that underwent 2 MDCT at different time points with a median interval of 13 months (interquartile: 10-17 months) were retrospectively evaluated. In-house software YACTA quantified automatically lung density histogram (10(th)-90(th) percentile in 5(th) percentile steps). Longitudinal changes in VSs and in the percentiles of attenuation histogram were obtained in 20 untreated patients and 20 patients treated with pirfenidone. Pearson correlation analysis was used to test the relationship between VSs and selected percentiles. RESULTS: In follow-up MDCT, visual overall extent of parenchymal abnormalities (OE) increased in median by 5 %/year (interquartile: 0 %/y; +11 %/y). Substantial difference was found between treated and untreated patients in HU changes of the 40th and of the 80th percentiles of density histogram. Correlation analysis between VSs and selected percentiles showed higher correlation between the changes (Δ) in OE and Δ 40(th) percentile (r=0.69; p<0.001) as compared to Δ 80(th) percentile (r=0.58; p<0.001); closer correlation was found between Δ ground-glass extent and Δ 40(th) percentile (r=0.66, p<0.001) as compared to Δ 80(th) percentile (r=0.47, p=0.002), while the Δ reticulations correlated better with the Δ 80(th) percentile (r=0.56, p<0.001) in comparison to Δ 40(th) percentile (r=0.43, p=0.003). CONCLUSIONS: There is a relevant and fully automatically measurable difference at MDCT in VSs and in histogram analysis at one year follow-up of IPF patients, whether treated or untreated: Δ 40(th) percentile might reflect the change in overall extent of lung abnormalities, notably of ground-glass pattern; furthermore Δ 80(th) percentile might reveal the course of reticular opacities.