Abstract: ⁹⁹Tc^m labelled colloidal rhenium suulphide was prepared from NANOCIS^® kit which was currently used for sentinel node detection clinically. After the labelling, the reaction solution was diluted into 10, 100, 500 and 715 folds, and respectively injected to the animals and biodistribution studies were carried out subsequently 1 h and 4 h postinjection. The effect of injected volume was also examined by administration of the same quantity but different volume of the labelled agent. In a separate biodistribution study, 3 g/L gelatin solution was used for the dilution and the function of gelatin was further evaluated. The results of biodistribution demonstrated that the uptake of SLN decreased while the retention at the injection site as well as popliteal extraction rate (PE%, refers to sentinel node extraction rate in this case) increased as the injected dosage went down. If more volume was injected as the quantity remained the same, the retention at the injection site increased and PE% decreased. When extra gelatin was added, the retention at the injection site and PE% decreased as the uptake of SLN increased. It could be concluded that gelatin in the NANOCIS kit acts as a stabilizer that will prevent the formation of aggregates and the dosage administered to the animals especially after dilution of reaction solution played a crucial role in the biological evaluation on SLN imaging agents.