Two-phase CT pulmonary angiography for detection of hilar pulmonary thromboembolism

The purpose of this study was to assess the usefulness of two-phase CT pulmonary angiography (CTPA) for patients with suspected pulmonary thromboembolism (PE). Forty-four patients (in 48 studies) underwent two-phase CTPA. Fifteen sec after the injection of contrast material, an entire thorax scan was performed, and in the second phase the hilar territory was rescanned after a 15-sec delay. In the first phase, 25 subjects were scanned cranio-caudally (group A), and 23 caudal-cranially (group B). The mean attenuation values of the main pulmonary artery (MPA) and the ascending aorta (Ao) were measured. Perivenous artifacts in the right pulmonary artery (RPA) were also graded using a 4-point scale. The mean attenuation values in the MPA and Ao were higher in the first phase than in the second phase. The perivenous artifact scores at the first phase in groups A and B were severe in 12 and 15, moderate in 8 and 7, minimal in 4 and 1, and none in 1 and 0. The scores at the second phase were none in all cases. Two-phase CTPA produced good opacification of the RPA without major perivenous artifact and proved useful in the detection of PE in these areas. (author)