Analysis of the ratio of the main pulmonary artery to that of the aorta on chest CT in patients with combined pulmonary fibrosis and emphysema

Background: In many diseases, there is a relationship between the ratio of the diameter of the pulmonary artery (PA) to that of the aorta (Ao) on chest computed tomography (CT). The aim of this study is to examine whether the PA/Ao ratio at diagnosis of idiopathic pulmonary fibrosis(IPF) and combined pulmonary fibrosis and emphysema (CPFE) is associated with the pulmonary hypertension. At present time, there is no analysis of PA/Ao ratio in CPFE. Methods: The present study included 125 patients diagnosed with IPF or CPFE at a single center from April 2014 to March 2019. The diameters of the PA and Ao on chest CT at initial diagnosis were analyzed retrospectively.The images are classified according to An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline(2018). The diameter of the PA was measured at the subjective bifurcation. The diameter of the Ao was measured at the same slice. These imaging analysis were performed by two pulmologists. Results: The number of IPF and CPFE were 60(48％) and 65 (52％). IPF images were categorized into four types : UIP/ Probable/ Indeterminate/ Alternative Diagnosis, 33/ 37/ 48/ 7 cases, respectively. The mean PA and Ao diameters were 29.75mm and 34.75mm, and the mean PA/Ao ratio of IPF and CPFE were 0.830 and 0.883. The PA/Ao ratio is significantly increased in the IPF group (p the Indeterminate＋Alternative Diagnosis group (0.883 vs 0.825, p Conclusions: The progression of fibrosis or the presence of emphysema in CPFE may suggest pulmonary hypertension in pulmonary fibrosis.