Fig. 5

Ultrasound images of φ0.97-mm (a, c) and φ0.64-mm (b, d) guidewires. a, b: Images near the puncture site with the probe kept almost upright. Guidewires can be seen in the internal jugular vein. c, d: Images at the supraclavicular fossa with the probe tilted almost horizontally. The guidewires are visible within the brachiocephalic vein, which warrants the subsequent insertion of a dilator. Without tilting the probe under transverse imaging, the guidewire in the deep portion cannot be visualized due to interference from the clavicle. Note that the visibility of the large spring wire is more favorable. Arrow: guidewire; asterisk: subclavian vein; arrowheads: venous valve between the internal jugular and brachiocephalic veins