In cases of suspected PE, what imaging technique provides the definitive diagnosis?

The definitive diagnosis of pulmonary embolism (PE) is achieved through pulmonary angiography. This imaging technique involves the injection of a contrast dye into the pulmonary arteries, allowing for detailed visualization of blood flow in the lungs. It clearly shows any blockages or obstructions caused by emboli and is considered the gold standard for diagnosing PE due to its high specificity and sensitivity.

While other modalities such as CT scans can also be used effectively to identify PE, pulmonary angiography remains the most definitive, providing direct visualization of the vascular structures involved. The use of ultrasound is primarily for the evaluation of deep vein thrombosis, which can lead to PE, while X-rays are not sensitive or specific enough to diagnose PE.