Figure 10b. (a) Truncus arteriosus. Combined CT scan and VR image show the truncus arteriosus (TA), from which the ascending aorta (aA) and pulmonary trunk (PT) arise. (b) Aortopulmonary window. VR image shows a distal aortopulmonary window (*), through which the ascending aorta (aA) and pulmonary trunk (PT) communicate with each other.