Dual-Energy CT for Pulmonary Embolism: Current and Evolving Clinical Applications

Abstract

Pulmonary embolism (PE) is a potentially fatal disease if the diagnosis or treatment is delayed. Currently, multidetector computed tomography (MDCT) is considered the standard imaging method for diagnosing PE. Dual-energy CT (DECT) has the advantages of MDCT and can provide functional information for patients with PE. The aim of this review is to present the potential clinical applications of DECT in PE, focusing on the diagnosis and risk stratification of PE.

Keywords: Chronic thromboembolic pulmonary hypertension; Dual-energy computed tomography; Iodine; Pulmonary artery sarcoma; Pulmonary embolism.

Fig. 1. A 76-year-old female diagnosed with acute pulmonary thromboembolism.

A. CT angiography showing a focal filling defect in the right upper lobar pulmonary artery (arrow) due to acute pulmonary thromboembolism and bilateral pleural effusion. B. The fusion image of CT angiography and a color-coded iodine map showing a thrombus in the right upper pulmonary artery as well as a corresponding wedge-shaped perfusion defect in the right upper lobe.

Fig. 2. A 30-year-old female diagnosed with acute pulmonary thromboembolism.

A. The conventional image with 100 kVp showing a focal filling defect in the right lower subsegmental artery. B. A monoenergetic image with 60 keV better depicting a subsegmental thrombus in the right lower lobe.

Fig. 3. A 58-year-old female with pulmonary artery sarcoma.

A. A coronal contrast enhanced CT image showing an intraluminal mass with an eccentric filling defect in the right main pulmonary trunk. B. On a coronal color-coded iodine (water) image from dual-energy CT, the mean iodine concentration within the region of interest is 2.6 mg/mL. C. A coronal PET image showing focal fluorodeoxyglucose uptake in the intraluminal mass and right upper paratracheal lymph nodes.

Fig. 4. A 34-year-old male with acute pulmonary embolism.

A. A color-coded iodine map showing multifocal perfusion defects in both upper lobes due to pulmonary thromboembolisms. B. A map obtained with a volume analysis software showing a perfusion defect volume, measured from −1024 to −1 Hounsfield units, of 324.15 cm³ and a relative perfusion defect volume of 10.24%.

Fig. 5. A 60-year-old male diagnosed with chronic pulmonary thromboembolism.

A. CT angiography image showing organized thrombi in both the main pulmonary arteries. B. In the pulmonary artery phase, a fusion image of CT angiography and color-coded iodine map showing organized thrombi in both main pulmonary arteries (arrows) with a wedge-shaped perfusion defect in the right upper lobe. C. On the delayed-phase image, the area with a previous perfusion defect in the right upper lobe is enhanced due to the systemic collateral supply in chronic pulmonary thromboembolism.

Fig. 6. A 74-year-old female with chronic pulmonary embolism.

A. CT angiography showing an eccentric chronic thrombus in the right lower pulmonary artery. B. The fusion image of CT angiography and color-coded iodine map showing a large eccentric chronic thrombus in the dilated right lower lobar pulmonary and multifocal perfusion defects in both lungs. C, D. After pulmonary endarterectomy, the organized thrombus was removed. The follow-up CT angiography image showing the contrast-enhanced right lower pulmonary artery after removal of the organized thrombus. An iodine map image demonstrates improved pulmonary perfusion on both lungs.

Fig. 7. A 50-year-old male suddenly complained of dyspnea after removal of a central venous catheter on day 5 after distal pancreatectomy and splenectomy.

A. Chest X-ray on day 4 after the operation showing the normal position of the central venous catheter through the right internal jugular vein. B, C. Abdominal CT on day 4 after the operation showing dependent atelectasis without embolic lesions (B). Chest CT image after dyspnea is presented (C). Multifocal air is suspected in the right middle pulmonary arteries (arrows in C), which was not noted in the previous abdominal CT (arrows in B), and hypoattenuations in both anterior lungs can be seen. D. The fusion image of CT angiography and a color-coded iodine map showing large perfusion defects in the anterior portion of both lungs, which could have been caused by pulmonary air embolism. CT = computed tomography

Fig. 8. A 73-year-old male diagnosed with chronic pulmonary thromboembolism.

A, B. A gray scale (A) and a fusion image iodine map (B) shows that the right middle lobe and left lingular segment (arrows) which abut the cardiac border also cause heterogeneous artifacts due to cardiac motion.