Clinical diagnosis of PE is difficult and it is frequently under- and over-diagnosed. Imaging diagnosis required in most cases because treatment has complications and costs. CTPA (or V/Q scan) first test if no DVT symptoms and Pulmonary angiography as ultimate confirmatory test with low morbidity and mortality. In patients suspected of having pulmonary embolism further workup with imaging is usually necessary. Nowadays, CT pulmonary angiography is the most widely used diagnostic modality with higher sensitivity and specificity than VQ scanning. VQ scanning remains a valid modality, although its result will be non-diagnostic in more than 60% of all screened patients. Since the ability of CTPA to depict smaller, isolated subsegmental pulmonary emboli appears to be suboptimal, the key question is what is the outcome of patients with negative spiral CT scans who do not undergo anticoagulation. Several studies looked into this, both pro- and retrospective in design. They uniformly found that the recurrence of PE in these patients is low and comparable to that after a negative or low probability VQ scan or negative pulmonary arteriogram. Thus, CTPA in conjunction with D-Dimer testing is considered a reliable imaging tool for the exclusion of clinically important PE.

CTPA valuable diagnostic tool with overall high sensitivities and specificities. CTPA is possibly more effective than V/Q scanning in the diagnosis and screening of PE. CTPA reduces likelihood of requiring further diagnostic tests as compared to scinthigraphy (Van Rossum Eur Radiol 1999). CTPA is more likely to yield alternative diagnosis if no PE exists (Shah Radiology 1999, Remy-Jardin Radiology 1999).