Diagnosis of acute pulmonary embolism: Conparison of CT pulmonary angiography and ventilation-perfusion scintigraphy

Objectives A pulmonary embolism (PE) is a blockage of a pulmonary artery usually caused by an embolus. This can be diagnosed using Ventilation / Perfusion scintigraphy (V/Q) showing absent perfusion and normal ventilation of the affected lung segment or using CT pulmonary angiography (CTPA). In this case iodinated contrast medium is injected i.v. and pulmonary embolism (PE) is shown as filling detect of the affected pulmonary artery. The goal of our study was to compare results of V/Q and the results of CTPA with aim to propose recommendation when to perform CTPA or V/Q scintigraphy.

Methods We compared results of V/Q planar scintigraphy in four projections and CTPA in 36 patients. Scintigraphic results were classified as low, intermediate and high probability of PE and affected lung segments were identified. CTPA was read as positive or negative and embolized arteries were identified.

Results 18 patients (50%) were classified as low probability, 14 patients (38.9%) as intermediate probability and 4 patients (11.1%) as high probability. CTPA identified PE in 3/18 (16.6%) patients with low probability, in 4/14 patients (28.5%) with intermediate and in all 4 patients with high scintigraphic probability of PE.

Conclusions It is necessary to perform CTPA in all patients with intermediate scintigraphic probability of PE, including cases of abnormal perfusion scan and ventilation scintigraphy not successfully or completely done, and also in patients with low probability scans and high clinical suspicion/probability of PE