FIGURE 4. (A) Time–radioactivity curves from region-of-interest (ROI) analysis after dynamic recording of lymphoscintigraphy performed by intradermal injection of 6 MBq (150 µCi) ^99mTc-HSA nanocolloid; y-scale is arbitrary to plot all 3 curves within same order of magnitude. Injection site shows minimal reduction over 60 min, barely discernible from physical decay. Tracer appears in sentinel node starting few minutes after injection, with quasiplateau maintained over 60 min. Lymphatic channel shows early passage of radioactivity, continuing with quasipulsatile pattern. Direct supply of radiocolloid draining from injection site (continuing over several hours) keeps radioactivity content of sentinel node at relatively higher level than that of second- or third-tier nodes, even if active retention of tracer by macrophages is saturated. (B) Definition of 3 ROIs on representative frame set from dynamic recording: ROI 1 = injection site; ROI 2 = lymphatic channel; ROI 3 = sentinel node.