Venous phase spectral or dual energy (DE) chest computed tomography (CT) in patients with suspected pulmonary embolism (PE) compared to standard computed tomography pulmonary angiography (CTPA): sensitivity, evaluation of iodine mapping and incidental findings.

Background/rationale: DE CTPA provides additional anatomical and functional information in the investigation of PE, especially in regards of iodine uptake in pulmonary vasculature and lung parenchyma. Postprocessing techniques improve visualisation of low concentrations of iodine contrast media.This has shown potential in reducing the amount of contrast media, salvaging scans with suboptimal contrast enhancement and for improving visualisation of incidental pulmonary embolisms in portal venous chest CT scans. Other significant DE postprocessing techniques include the substraction of iodine, creating virtual non-contrast images in addition to the dual energy. This technique has proven useful in evaluation of different thoracic and abdominal parenchymal lesions.

Objective: To evaluate sensitivity of chest DECT in portal venous phase in the diagnosis of PE compared to standard care DE CTPA. Furthermore, the prevalence and management of incidental findings will be evaluated.

Design: Patients enrolled in this study will undergo a venous phase chest DE CT in addition to standard care DE CTPA. The two scans will be performed consecutively using the same contrast media bolus. Standard DE reconstructions of all scans will be obtained for radiological evaluation and reporting in regards of suspected PE.

Both scans with standard DE reconstructions will be available for clinical evaluation and patient care in the standard care AGFA PACS system. Radiological reading and reporting will be performed as usual in the clinical setting.

For research purposes, additional post-processing procedures may be performed by the readers in Philips IntelliSpace Portal or Siemens Syngo.via depending on the scanner applied. The standard CTPA will be interpreted by a thoracic radiologist and used as reference. The corresponding portal venous chest CT will be interpreted individually by two other certified radiologists in order to avoid recall bias. In case of disagreement in the venous chest CT, an independent radiologist not elsewhere involved will be consulted. If a PE detected on the portal venous scan is not detected on the reference CTPA, the reference reader will re-evaluate the CTPA.

Patient characteristics, clinical information, radiation dose, contrast media, clinical diagnosis, incidental findings and recommendations of further clinical management according to clinical guidelines will be recorded in a secure web-based database.

Study population: Patients aged ≥50 with suspected pulmonary embolism who are having performed a standard care CTPA.

Inclusion Criteria:

• Patients suspected for pulmonary embolism undergoing a computed tomography pulmonary angiography
• Minimum age 50 years

Exclusion Criteria:

• Temporarily or permanently incompetent patient not able to give informed consent
• No informed consent obtained for other reasons
• Allergic to iodine based contrast media
• Impaired renal function
• Patients with thyreotoxicosis
• Non-diagnostic quality of computed tomography images