From the case:
Vascular pedicle (diagram)
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The vascular pedicle is bordered on the right by venous structures (right brachiocephalic vein above and superior vena cava) and on the left by an arterial structure (the left subclavian artery origin). The azygos vein (black oval) is seen en face above the right main bronchus.
The vascular pedicle width (VPW) is the distance between parallel lines drawn from the point at which the superior vena cava intersects the right main bronchus an a line drawn at the takeoff of the left subclavian artery from the aorta. The mean vascular pedicle width is 38-58 mm on posteroanterior chest radiographs.