The internal mammary vessels above and below the first rib on multidetector CT: implications for anatomical feasibility of lung biopsy via anterior approach.

PURPOSE To provide the anatomical knowledge necessary to draw biopsy routes by using an anterior approach above and below the first rib to avoid internal mammary vessel damage. MATERIALS AND METHODS The anatomy of internal mammary vessels above and below the first rib was assessed by thin-section computed tomography (CT) analysis of 61 adults. The visibility of the internal mammary vessels, the relationship with the brachiocephalic vein, and the distance from the first rib (window width for biopsy) were determined above the first rib, whereas whether and where the internal mammary artery (IMA) and/or internal mammary vein (IMV) crossed the rib margin were assessed below the first rib. RESULTS There was no bony interval between the clavicle and the first rib on 5 sides (four patients). On the remaining 117 sides, 117 IMAs and no IMVs were seen (18 IMAs were seen on contrast-enhanced CT only). The window width for biopsy was 5 mm or greater on 82 sides (right: 30, left: 52) and was significantly wider on the left side (right: 4.7-5.7 mm, left: 8.2-9.0 mm) (P < 0.05). The inferolateral margin of the first rib was crossed by 99 IMAs and 93 IMVs, which were mostly within the caudalmost 5 mm. CONCLUSION Above the first rib, a biopsy route at least 5 mm away from the IMA often exists and is often identifiable by its characteristic appearance on noncontrast CT (nipple on lateral margin of the brachiocephalic vein). The internal mammary vessels are not present on the inferior margin of the first rib except in the caudalmost 5 mm of its cartilage.