Dual-layer dual-energy CT-derived pulmonary perfusion for the differentiation of acute pulmonary embolism and chronic thromboembolic pulmonary hypertension

Abstract

Objectives: To evaluate dual-layer dual-energy computed tomography (dlDECT)-derived pulmonary perfusion maps for differentiation between acute pulmonary embolism (PE) and chronic thromboembolic pulmonary hypertension (CTEPH).

Methods: This retrospective study included 131 patients (57 patients with acute PE, 52 CTEPH, 22 controls), who underwent CT pulmonary angiography on a dlDECT. Normal and malperfused areas of lung parenchyma were semiautomatically contoured using iodine density overlay (IDO) maps. First-order histogram features of normal and malperfused lung tissue were extracted. Iodine density (ID) was normalized to the mean pulmonary artery (MPA) and the left atrium (LA). Furthermore, morphological imaging features for both acute and chronic PE, as well as the combination of histogram and morphological imaging features, were evaluated.

Results: In acute PE, normal perfused lung areas showed a higher mean and peak iodine uptake normalized to the MPA than in CTEPH (both p < 0.001). After normalizing mean ID in perfusion defects to the LA, patients with acute PE had a reduced average perfusion (ID_mean,LA) compared to both CTEPH patients and controls (p < 0.001 for both). ID_mean,LA allowed for a differentiation between acute PE and CTEPH with moderate accuracy (AUC: 0.72, sensitivity 74%, specificity 64%), resulting in a PPV and NPV for CTEPH of 64% and 70%. Combining ID_mean,LA in the malperfused areas with the diameter of the MPA (MPA_dia) significantly increased its ability to differentiate between acute PE and CTEPH (sole MPA_dia: AUC: 0.76, 95%-CI: 0.68-0.85 vs. MPA_dia + 256.3 * ID_mean,LA - 40.0: AUC: 0.82, 95%-CI: 0.74-0.90, p = 0.04).

Conclusion: dlDECT enables quantification and characterization of pulmonary perfusion patterns in acute PE and CTEPH. Although these lack precision when used as a standalone criterion, when combined with morphological CT parameters, they hold potential to enhance differentiation between the two diseases.

Clinical relevance statement: Differentiating between acute PE and CTEPH based on morphological CT parameters is challenging, often leading to a delay in CTEPH diagnosis. By revealing distinct pulmonary perfusion patterns in both entities, dlDECT may facilitate timely diagnosis of CTEPH, ultimately improving clinical management.

Key points: • Morphological imaging parameters derived from CT pulmonary angiography to distinguish between acute pulmonary embolism and chronic thromboembolic pulmonary hypertension lack diagnostic accuracy. • Dual-layer dual-energy CT reveals different pulmonary perfusion patterns between acute pulmonary embolism and chronic thromboembolic pulmonary hypertension. • The identified parameters yield potential to enable more timely identification of patients with chronic thromboembolic pulmonary hypertension.

Keywords: Acute pulmonary embolism; Chronic thromboembolic pulmonary hypertension; Computed tomography; Pulmonary perfusion.

Fig. 1

Study flow chart. PE, pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension; CTED, chronic thromboembolic disease. *For example, pleural effusion, pneumonia, pulmonary oncologic manifestations. Pulmonary fibrosis and emphysema were not exclusion criteria

Fig. 2

Conventional reconstructions (A1–A6), corresponding IDO images (B1–B6), and automatically derived normal (C1–C6) and malperfused lung areas (D1–D6) illustrating the physiological ventro-dorsal gradient of pulmonary blood volume in the supine patient as well as the visually similar perfusion patterns in acute PE (middle) and CTEPH (bottom). IDO, iodine density overlay; APE, acute pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension

Fig. 3

Box (25th percentile, median, and 75th percentile) and whisker (10th and 90th percentile) plots for ID_skewness in malperfused lung areas (A) and diagnostic accuracy of ID_skewness in malperfused lung areas for acute PE/CTEPH based on AUC analysis in the training dataset (B) and the test dataset (C). ID, iodine density; AUC, area under curve; APE, acute pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension

Fig. 4

dlDECT-based assessment of pulmonary perfusion via systemic collaterals in a patient with acute PE (top) and a patient suffering from CTEPH (bottom). Axial and paracoronar multiplanar reconstructions show the enlarged bronchial arteries (>1.5 mm) in the CTEPH patient (B3 and B4) leading to an increased perfusion in embolic lung areas as indicated by an increased ID_mean,LA (C1/2 vs. C3/4). APE, acute pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension; ID, iodine density; LA, left atrium

Fig. 5

Box (25th percentile, median, and 75th percentile) and whisker (10th and 90th percentile) plots of ID_mean,LA in malperfused lung areas. ID, iodine density; LA, left atrium; APE, acute pulmonary embolism; CTEPH, chronic thromboembolic pulmonary hypertension