Detection of patients with chronic thromboembolic pulmonary hypertension by volumetric iodine quantification in the lung-a case control study

Background: To evaluate whether volumetric iodine quantification of the lung allows for the automatic identification of patients with chronic thromboembolic pulmonary hypertension (CTEPH) and whether the extent of pulmonary malperfusion correlates with invasive hemodynamic parameters. Methods: Retrospective data base search identified 30 consecutive patients with CTEPH who underwent CT pulmonary angiography (CTPA) on a spectral-detector CT scanner. Thirty consecutive patients who underwent an identical CT examination for evaluation of suspected acute pulmonary embolism and had no signs of pulmonary embolism or PH, served as control cohort. Lungs were automatically segmented for all patients and normal and malperfused volumes were segmented based on iodine density thresholds. Results were compared between groups. For correlation analysis between the extent of malperfused volume and mean pulmonary artery pressure (mPAP) and pulmonary vascular resistance (PVR) 3 patients were excluded because of a time span of more than 30 days between CTPA and right heart catheterization. Results: Patients with CTEPH had a higher percentage of malperfused lung compared to controls (43.25%+/- 24.72% vs. 21.82%+/- 20.72%; P=0.001) and showed reduced mean iodine density in malperfused and normal-perfused lung areas, as well as in the vessel volume. Controls showed a left-tailed distribution of iodine density in malperfused lung areas while patients with CTEPH had a more symmetrical distribution (Skew: -0.382 +/- 0.435 vs. -0.010 +/- 0.396; P=0.004). Patients with CTEPH showed a significant correlation between the percentage of malperfused lung volume and the PVR (r=0.57, P=0.001). Conclusions: Volumetric iodine quantification helps to identify patients with CTEPH by showing increased areas of malperfusion. The extent of malperfusion might provide a measurement for disease severity in patients with CTEPH.