Imaging Modalities in Acute Pulmonary Embolism: Computerized Tomography

Computerized tomography pulmonary angiography (CTPA) is currently the imaging modality of choice for the workup of suspected acute pulmonary embolism (PE) with high sensitivity, specificity, negative and positive predictive values. As such, CTPA is at the core of the pathway for the diagnosis and management of PE. Correct and timely performance, interpretation and reporting of CTPA studies is mandatory for successful management of patients with acute PE, and greatly depends on various elements, from the moment the patient is lying in the CT machine to the delivery of the report. In the following chapter, we systematically cover these elements along with multiple CT images of both normal and pathological appearance of pulmonary arteries, lungs and mediastinum. We review the main technical considerations for achieving high image quality and avoiding artifacts, thus reducing the number of indeterminate studies, while minimizing as much as possible radiation dose and contrast material volume. We present both normal and pathological CTPA appearance of the pulmonary arteries, including the classic appearances and signs of PE, common lung parenchyma findings and CT predictors of PE severity and clinical outcome. Recent technological developments have introduced new CTPA tools and capabilities, further improving diagnosis, risk assessment and timely reporting. Dual energy CT (DECT) enables to create perfusion maps of lung parenchyma, improving the ability to detect small subsegmental PE and to assess the effect of PE on lung parenchyma. By improving arterial enhancement, DECT improves PE detection, may salvage technically low quality studies and may enable reduction in contrast material volume and radiation dose. Another recent tool in use is artificial intelligence (AI) algorithms for automatic PE detection. AI algorithms can improve inexperienced readers’ accuracy, can shorten CTPA reading times and can detect incidental PE in CT examinations performed for other indications in a non-CTPA protocol.