A pulmonary embolism (PE) refers to the blockage of the pulmonary vasculature by an embolus (a blood clot). About 95% of pulmonary emboli begins as a thrombus in the deep venous system of the lower limbs, which travels to the lungs and lodges either at bifurcation of the main pulmonary artery or one of the branches of the pulmonary trunk. Smaller thrombi usually travel further and lodge in the smaller blood vessels in the lung periphery.
Despite advances in medical imaging technology, diagnosis of PE remains challenging: approximately 100,000 deaths each year could be prevented with prompt and accurate diagnosis. The current gold standard in the diagnosis of PE is computed tomography pulmonary angiography (CTPA) scanning. CTPA is quick and easy to read and has a high degree of sensitivity and specificity.