Abstract :
Byline: Chris Tsopelas (1), Max Bellon (1), Elaine Bevington (2), James Kollias (2), Sabah Shibli (2), Barry E. Chatterton (1) Keywords: Radioactive blue dye; Lymphoscintigraphy; Sentinel lymph node; Evans Blue Abstract: Objective [.sup.99m]Tc-Evans Blue (EB) is an agent that contains both radioactive and color signals in a single dose. Earlier studies in animal models have suggested that this agent when compared with the dual-injection technique of radiocolloid/blue dye can successfully discriminate the sentinel lymph node. The aim of this study was to investigate the potential of 99m.sup.Tc-EB as an agent to map the lymphatic system in an ovine model. Methods Doses of 99m.sup.Tc-EB (23 MBq) containing EB dye (4 mg) were administered intradermally to the limbs of four anesthetized sheep, and they were then imaged over 20--30 min using a gamma camera. The study protocol was repeated using 99m.sup.Tc-antimony trisulfide colloid (ATC) and Patent Blue V dye. The lymph nodes (popliteal, inguinal, and iliac for hind limbs or prescapular for fore limbs) were identified with a gamma probe during the operative exposure, then dissected and counted in a large volume counter. Results Simple and complex (dual) drainage patterns were visible on the scans, and the sentinel node was more radioactive than higher tier nodes in a chain, for both radiotracers. For 99m.sup.Tc-EB, maximum radioactive uptake was achieved at 3--6 min for popliteal lymph nodes, 12--14 min for iliac nodes, and 13--14 min for prescapular nodes. 99m.sup.Tc-ATC resulted in maximum radioactive uptake at 4--6 min for popliteal lymph nodes, 13 min for an inguinal node, 13--20 min for iliac nodes, and 18 min for a prescapular node. Following 99m.sup.Tc-EB injection, 15/15 lymph nodes harvested were all radioactive and blue. For 99m.sup.Tc-radiocolloid/Patent Blue V injection, 8/14 nodes were radioactive and blue, and 6/14 nodes were radioactive only. Conclusions The soluble radiotracer 99m.sup.Tc-EB appeared to be a useful lymphoscintigraphic agent in sheep, in which radioactive counts from superficial lymphatic channels and lymph nodes were sufficient for planar imaging. In comparison with 99m.sup.Tc-antimony trisulfide colloid, both tracers discriminated the sentinel lymph node up to 50 min after administration however, 99m.sup.Tc-EB had the advantage of providing radioactive (gamma probe) and color signals simultaneously during the operative exposure. Author Affiliation: (1) Nuclear Medicine Department, Royal Adelaide Hospital, North Terrace, Adelaide, SA, 5000, Australia (2) Department of Breast and Endocrine Surgery, Royal Adelaide Hospital, Adelaide, SA, Australia Article History: Registration Date: 25/11/2008 Received Date: 12/05/2008 Accepted Date: 06/06/2008 Online Date: 28/11/2008