Lymphatic mapping with 99mTc-Evans Blue dye in sheep.
OBJECTIVE
99mTc-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 99mTc-EB as an agent to map the lymphatic system in an ovine model.


METHODS
Doses of 99mTc-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 99mTc-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 99mTc-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. 99mTc-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 99mTc-EB injection, 15/15 lymph nodes harvested were all radioactive and blue. For 99mTc-radiocolloid/Patent Blue V injection, 8/14 nodes were radioactive and blue, and 6/14 nodes were radioactive only.


CONCLUSIONS
The soluble radiotracer 99mTc-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 99mTc-antimony trisulfide colloid, both tracers discriminated the sentinel lymph node up to 50 min after administration; however, 99mTc-EB had the advantage of providing radioactive (gamma probe) and color signals simultaneously during the operative exposure.
Tsopelas
Chris
C
Nuclear Medicine Department, Royal Adelaide Hospital, North Terrace, Adelaide, SA, 5000, Australia. Chris.Tsopelas@health.sa.gov.au
Bellon
Max
M
Bevington
Elaine
E
Kollias
James
J
Shibli
Sabah
S
Chatterton
Barry E
BE
D000818:Animals; D005070:Evans Blue; D008198:Lymph Nodes / Q000000981:diagnostic imaging* / Q000473:pathology*; D008297:Male; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012756:Sheep; D013667:Technetium
D019275:Radiopharmaceuticals; D005070:Evans Blue; D013667:Technetium