Figure 2b. Normal anatomy at MR imaging in one patient. (a) Axial T1-weighted image through the apex of the lung shows the trunks of the brachial plexus (arrowheads) posterior to the subclavian artery (solid black arrow) and vein (open arrow) and just anterior to the serratus anterior muscle (white arrow). (b) Oblique sagittal T1-weighted image shows the individual cords of the brachial plexus (arrowheads) adjacent to the subclavian artery (straight arrow) and vein (curved arrow). (c) Coronal T1-weighted image demonstrates the cords of the brachial plexus (arrowheads) adjacent to the subclavian artery (solid arrow) and just superior to the subclavian vein (open arrow).