Interstitial MR lymphangiography for the detection of sentinel lymph nodes

Background and Objectives: The challenge for implementation of sentinel lym ph node biopsy is to develop a reliable minimally invasive technique that i dentifies all possible sentinel nodes with high temporal and spatial resolu tion. This study evaluated the use of a magnetic resonance imaging (MRI) co ntrast agent (USPIO) for preoperative sentinel node detection. Methods: Anesthetized pigs received interstitial or intradermal injections of ultra small superparamagnetic of iron oxide (USPIO) (0.2 or 5 mg Fe) in the L/R posterior tongue and stifles (knee) respectively. MRI was done befo re, during injection and at 0.25, 0.5, 1, 2, 4, 6, 24, and 48 hr after whic h isosulfan blue sentinel node mapping was done. Results: In the tongue, both doses of USPIO identified the sentinel node in the early images. No additional nodes were detected by MR at 24 or 48 hr. In the hind limb, sentinel nodes identified on the early MR images were als o identified by the isosulfan blue. In both locations, the higher dose also identified secondary nodes some of which were also identified by the isosu lfan blue. All sentinel nodes that were identified by USPIO on MRI were not ed to be stained brown at the time of dissection. Conclusions: Interstitial MR lymphangiography is a useful technique for the detection of sentinel lymph nodes. This method provides excellent simultan eous temporal and spatial resolution, is minimally invasive, and can be per formed preoperatively. (C) 2001 Wiley-Liss, Inc.