In X-Ray right border of mediastinum is formed by all except:
C i.e. Right Ventricle Right hea border on chest x-ray PA view is formed by right atrium with its draining tributaries SVC & IVCQ. Right aspect of ascending thoracic aoa and right innominate/brachiocephalic vesselsQ are also involved sometimes in forming right border. But right ventricle does not form the right border of the hea or mediastinum. It forms the anterior border of hea visible on lateral film.
SVC
Right Atrium
Right Ventricle
Right Brachiocephalic Vein