Pulmonary arteries typically follow their respective segmental and subsegmental bronchi. Therefore, if one knows segmental bronchial anatomy, the objective is already mostly achieved. However, normal variation abounds and is most common in the upper lobes. The most common variants should be kept in mind when attempting to follow the pulmonary arteries at CT. A systematic approach to interpretation should minimize interpretive errors.

Diagnostic signs of pulmonary embolism at CTPA have been previously discussed in the radiological literature. Our focus remains to elaborate a systematic approach to evaluating all of the pulmonary arteries visible at CTPA rather than to further discuss the imaging findings that constitute a positive examination. When interpreting a CTPA, one should first examine the other thoracic structures, such as the airways, lung parenchyma, mediastinum and hila, chest wall, and upper abdomen. Then, a deliberate, stepwise examination of the pulmonary arteries can be performed, as outlined in the next pages.