Imaging evaluation often begins with a chest x-ray. In acute PE, it is most often normal. Occasionally, it may show subsegmental atelectasis or consolidation. Hampton's hump and Westernmark's signs are rare, non-specific, and have little practical utility. These too have problems.
Pulmonary angiography is accurate, but invasive and expensive.
Again, not an ideal situation. HCT is designed to accomplish large volume acquisitions in a breathhold, limiting motion artifact related to respiration, heart activity, etc. This technology is expensive and its other applications are limited. As a result, electron-beam CT has not flourished in practice. It is often argued that helical CT has limited accuracy for subsegmental emboli.