Lobar pulmonary perfusion quantification with dual-energy CT angiography: Interlobar variability and relationship with regional clot burden in pulmonary embolism.

Purpose: Semi-automated lobar segmentation tools enable an anatomical assessment of regional pulmonary perfusion with Dual-Energy CTA (DE-CTA). We aimed to quantify lobar pulmonary perfusion with DE-CTA, analyze the perfusion distribution among the pulmonary lobes in subjects without cardiopulmonary diseases and assess the correlation between lobar perfusion and regional endoluminal clots in patients with acute pulmonary embolism (PE). Methods: We evaluated 151 consecutive subjects with suspected PE and without cardiopulmonary comorbidities. DE-CTA derived perfused blood volume (PBV) of each pulmonary lobe was measured applying a semi-automated lobar segmentation technique. In patients with PE, blood clot location was assessed, and CT-based vascular obstruction index of each lobe (CTOIlobe) was calculated and classified into three groups: CTOIlobe= 0, low CTOIlobe (1-50%) and high CTOIlobe (>50%). Results: Among patients without PE (103/151, 68.2%), median lobar PBV was 13.7% (IQR 10.2-18.0%); the right middle lobe presented lower PBV when compared to all the other lobes (p < .001). In patients with PE (48/151, 31.8%), lobar PBV was 12.6% (IQR 9.6-15.7%), 13.7% (IQR 10.1-16.7%) and 6.5% (IQR 5.1-10.2%) in the lobes with CTOIlobe= 0, low CTOIlobe and high CTOIlobe scores, respectively, with a significantly decreased PBV in the lobes with high CTOIlobe score (p < .001). ROC analysis of lobar PBV for prediction of high CTOIlobe score revealed AUC of 0.847 (95%CI 0.785-0.908). Conclusion: Pulmonary perfusion was heterogeneously distributed along the pulmonary lobes in patients without cardiopulmonary diseases. In patients with PE, the lobes with high vascular obstruction score (CTOIlobe> 50%) presented a decreased lobar perfusion.