Figure 2.

CTPA in mediastinal window setting (WW 400; WL 100) compares vascular enhancement at the level of main pulmonary artery (A) showing enhancement of 310.8 HU which is close to the average in 120 kV group and (B) showing a much higher enhancement of 513.5 HU that was noted in the 100 kV protocol. Circles indicate the region of interest of 1.0 cm² (±0.5) that was used to measure the average CT number at the main pulmonary artery. CTPA, computed tomography pulmonary angiography; WW, window width; WL, window level; HU, Hounsfield unit; kV, kilovoltage.