Figure 2.

Nonradioactive NIRF imaging of [¹⁹F]Lymphoseek 3. (A) Typical NIRF imaging experiment of a mouse that had been injected with 1 nmol of [¹⁹F]3 diluted with 10 nmol of unconjugated Lymphoseek. The NIRF signal (colored red) is overlaid onto a bright field image (green) of a mouse. A red arrow indicates clear localization of [¹⁹F]Lymphoseek 3 to the sentinel (popliteal) lymph node, while the blue arrow indicates localization to the distal (lumbar) lymph node. (i) Post-mortem skin-on image in which tissue (skin) notably interferes with the sentinel lymph node visibility. (ii) Pre-excision image (skin removed) in which the sentinel node visibility is improved and lymph drainage tracks are visible. (iii) Postoperative image in which the excised lymph nodes have been placed in the field of view. (B) In vivo imaging of [¹⁹F]Lymphoseek 3’s mannose receptor specific activity. Fluorescent [¹⁹F]Lymphoseek 3 (1 nmol) was imaged in the presence of 2 (i), 29 (ii), or 300 nmol (iii) of unlabeled Lymphoseek, a competitor for lymph node mannose binding sites. Note that lymph tracks are clearly visible and that greater accumulation of fluorescent [¹⁹F]Lymphoseek 3 is seen in the sentinel lymph nodes with 3 and 30 nmol injections than with 300 nmol injections because of increased competition with unlabeled Lymphoseek for sentinel lymph node mannose receptors. (C) Ex vivo imaging of [¹⁹F]Lymphoseek 3’s mannose receptor specific activity. Sentinel lymph nodes were extracted from mice and placed on a bed for analysis. Greater accumulation of fluorescent [¹⁹F]Lymphoseek 3 is seen in the sentinel lymph nodes in 3 nmol injections than in 300 nmol injections (signal ratio of 3.5, n = 3 mice per dose, P = 0.015 for a two-tailed test, two-sample equal variance, quantization shown in the Supporting Information).