Localization of breast sentinel lymph nodes by MR lymphography with a conventional gadolinium contrast agent. Preliminary observations in dogs and humans.

PURPOSE: To test the capability of an indirect MR lymphography (MRLG) using a conventional extracellular gadolinium (Gd)-based contrast agent for localizing breast sentinel lymph node (SLN).
METHODS: A total of 1 and 0.5 ml of undiluted gadopentetate dimeglumine were injected subcutaneously into the two periareolar areas overlying each caudal mammary gland in 10 female dogs. Contiguous 2-mm-thick fast gradient echo MR images were acquired through the upper breast and axilla before and for 60 min after gentle massage at the injection sites, yielding 3D displays. The localized SLN was resected from the living animals, followed by post mortem examinations. MRLG (1 ml contrast agent injected) was also attempted in 5 female volunteers.
RESULTS: Even with 0.5-ml contrast agent, the MRLG clearly visualized the connection of SLN and lymphatic vessels directly draining from the injection sites, and the remaining distant nodes, with the maximal enhancement peaks within 10 min after massage. The 3D images provided comprehensive anatomy of these lymphatic pathways in each axilla. Of the 20 SLN and 128 distant nodes visualized on the MRLG, all the SLN (100%) and 107 (83.5%) distant nodes could be resected pre- and post mortem, in good correlation with the locations and sizes on the MR images. MRLG also effectively localized SLN in the volunteers, without significant adverse effects.
CONCLUSION: An indirect MRLG using small volumes of conventional Gd-based contrast agent may have potential for accurate identification and surgical biopsy of breast SLN.