Radiological diagnosis of pulmonary embolism

Pulmonary embolism (PE) is often referred to as the great masquerader, and remains a diagnostic challenge in daily practice due to its mostly unspecific clinical presentation. Diagnostic algorithms are needed to assist clinical assessment and optimise the use of investigations, especially under emergency conditions. Nuclear medicine ventilation-perfusion (V/Q) scintigraphy has long been the imaging mainstay for the diagnosis of PE. Venous thromboembolism is not directly visualised but, rather, its effects on perfusion and ventilation. This necessitates the need for probability criteria, categorised as high, intermediate, low or very low probability, and normal. Spiral computed tomography pulmonary angiography (CTPA) emerged in the 1990s as a new diagnostic technique. CTPA has become the gold standard for the radiological assessment of a clinically suspected PE in daily practice. Special attention should be given to the clinical impact of incidental and subsegmental emboli.