Migration pathways of hypodermically injected technetium-99 m in dogs

Hypodermic injection of technetium-99m ((TC)-T-99m-pertechnetate) at points of low electrical resistance give rise to rapid, longitudinal, and progres sive diffusion of the radioactive tracer. We assessed the effect of cutaneo us incisions that did not intersect the migration trajectory of Tc-99m-pert echnetate and the re-establishment of pathways after the suture of incision s that intersected the migration trajectory. Linear and rapid migration of Tc-99m-pertechnetate was not altered or prevented by incisions that did not intersect the migration pathway. Different patterns of Tc-99m-pertechnetat e spread were found when incisions intersected the radioactive pathways unt il restoration of the normal migration pathway observed in undamaged skin o ccurred. In all experiments in which migration of Tc-99m-pertechnetate was observed, lavi: age of surgical wounds was followed by disappearance of the Tc-99m-pertechnetate migration observed around the suture. Linear migratio n of the tracer was not observed when the incision was left uncovered, fill ed with petroleum jelly or with a solid silicone sheet, but it was seen whe n non-sutured incisions were filled with transonic or silicone gel or cover ed with a solid silicone sheet parallel to the cutaneous plane. These data show that after a cutaneous incision that intersected the diffusion traject ory of the radioactive trac er, linear migration of Tc-99m-pertechnetate hy podermically injected at points of low electrical resistance was restored b efore healing of the cutaneous incision and was independent of incisions ma de on the skin not overlying the radioactive pathway. A mechanism similar t o that of capillary electrophoresis is suggested to explain the hypodermic diffusion of inert particles through specific and constant linear pathways.