Sentinel lymph node uptake of two different technetium-labeled radiocolloids

The study was designed to compare the uptake of technetium-99m-labeled human serum albumin ([99mTc]HSA) and 99mtechnetium-labeled sulfur colloid ([99mTc]SC) in the sentinel lymph nodes (SLNs). Radiocolloid levels in the SLN, femoral lymph node (FLN), ischial lymph node (ILN), spleen (SP), and right rear footpad (RRF) were quantitated over a period of 240 min after injection of [99mTc]SC or [99mTc]HSA into the rear footpad of C57 BL/6 mice. There was a significantly greater (p < 0.001) radioactive count in SLNs after [99mTc]SC (mean cpm 211,084.8) compared to [99mTc]HSA (mean cpm 115,640.8). In contrast, the counts in the FLNs were higher after [99mTc]HSA (mean cpm 11,333.4) than after [99mTc]SC injection (mean cpm 5,065.5). The percent uptake in the SP was higher after [99mTc]HSA than after [99mTc]SC injection. [99mTc]SC is rapidly and efficiently taken up by lymphatics at the primary injection site, is significantly retained in the SLN, and flows slowly to the next echelon node (FLN or ILN) and to the systemic circulation (SP). [99mTc]HSA tends to accumulate less efficiently in the SLN and to disperse more rapidly to the next echelon nodes and to the systemic circulation. By extrapolation, [99mTc]SC is likely to be a better radiocolloid for the intraoperative detection of SLNs.