Quantification of pulmonary fat attenuation volume (CTpfav) by computed tomography and its relationship with chronic pulmonary diseases

Objective: To quantitatively calculate the pulmonary fat attenuation volume (CTpfav) from thoracic CT images and determine its relationship with patient groups with radiologically usual interstitial pneumonia (UIP), nonspecific interstitial pneumonia (NSIP), bronchiectasis, emphysema, and normal imaging findings.Materials and Methods: Between January 1. 2021, and March 15. 2025, data from 468 patients over 18 years of age with UIP, NSIP, bronchiectasis, emphysema, and normal imaging findings from thoracic CT scans performed at Dicle University Faculty of Medicine Hospital were retrospectively evaluated. Lung volumes and segmentations were performed using a Syngo.via workstation, and CTpfav values were obtained by HU thresholding (between -40 and -200). The CTpfav values were then ratioed to the lung volume to obtain the pulmonary fat index (PFI). The data were compared between the groups and with the control group, and the relationship with the diseases was established.Findings: The CTpfav (mean 54.88±25.08 ml) and PFI (1.97±1.31) values in the UIP group were statistically significantly higher compared to all other patient groups, including the control group (CTpfav mean 32.16±15.70 ml, PFI 0.84±0.41). When the CTpfav values of the NSIP group (38.05±20.22 ml) were compared to the control group, there was no statistically significant difference; however, the PFI (1.57±1.07) showed a significant increase compared to the control group. The CTpfav values of patients in the bronchiectasis group (42.40±22.14 ml) were statistically significantly higher compared to the control group, while no significant difference was found in the PFI (1.05±0.59). In the emphysema group, the CTpfav values (41.31±18.86 ml) were significantly higher than in the control group, but the PFI (0.80±0.46) showed no significant difference.Conclusion: The increased CTpfav values in the UIP, bronchiectasis, and emphysema groups compared to the control group, and the increased PFI values in the UIP and NSIP groups compared to the control group, support the idea that these parameters can be used as a diagnostic or prognostic imaging biomarker. Accordingly, CTpfav can be considered a measure that may provide a quantitative contribution to conventional imaging assessments.Keywords: Pulmonary fat attenuation volume (CTpfav), Pulmonary fat index (PFI), Bronchiectasis, Usual interstitial pneumonia (UIP), Emphysema