Thyroidal venography. During parathyroid hormone venous sampling, the thyroidal veins are key to target as most abnormal tissue will be located in the neck. The superior and medial thyroidal veins empty into the internal jugular vein (asterisk). In this image, the superior thyroidal vein (arrowhead) has been cannulated and hand injection with prolonged imaging demonstrates the orifices of the middle thyroidal vein (arrow) at the caudal internal jugular vein, and the inferior thyroid trunk (double arrowhead), which empties into the left brachiocephalic vein (double asterisk).