Sentinel lymph node mapping using 99m Tc-labeled mannosyl-neoglycoalbumin and small semiconductor gamma camera for gastrointestinal cancers.

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Mannnosyl-neoglycoalbumin (NMA) is a small sized particle which has a capability to bind to mannose receptors on reticuloendotherial cells. Thus, it is expected to show rapid clearance from its injection sites and high retention within regional lymph nodes (LNs) if it is used as a tracer for sentinel lymph node (SLN) mapping. Semiconductor gamma camera (SGC) is small enough to use in an operating room and has higher spatial resolution specificity compared with conventional scintillation camera. A new technique to map SLNs for gastrointestinal cancers using a combination of 99mTc-labeled NMA and SGC was proposed and its usefulness was tested in a swine model.99mTc-labeled NMA was administered to both stomach and rectum of three specific pathogen free swines of three-month-old. Mean number of 3 LNs, even nodes adjacent to the injection site, were depicted within the regional LNs area of the organ. Clearance of the tracer from injection sites was two times faster, and retention in the LNs was four times higher as compared to 99m-labeled tin colloid, that were commonly used for SLN mapping of gastrointestinal cancers in our country, indicating an usefulness of the new tracer to avoid so-called "shine-through phenomenon".SGC was also refined with furnishing an optical camera and a capability to out put real-time fusion images of real and radioactive view, in order to facilitate to pinpoint radioactive nodes. SGC of this new version was also tested on surgical specimen of gastric cancer, and injection sites were precisely localized on the synthesized images, thus, indicating that this new SLN mapping technique is useful and ready for clinical use.