Abstract: Objective To evaluate the biodistribution and planar gamma carnera jmaging characteristics of ¹⁸⁸Re labeled insulin-like growth factor 1 analogue(¹⁸⁸Re-IGF-1A)in tumor-bearing mice.Methods ①To label IGF-1A with ¹⁸⁸Re directly and to determine the labeling efficiency.②To establish nude mice model which beating human pancreatic carcinoma cell Patu8988.③To scan those nude mice at 15 min,1 h,4 h,24 h,3 d and 5 d after intratumor injection with ¹⁸⁸Re-IGF-1A into their tumors.④To scan those nude mice at 15min,1 h,2h,4 h and24 h after intratumor injection with ¹⁸⁸ReO₄^-into their tumors.To calculate the tumor to normal tissue ratio(T/NT)and the percentages of injected dose per gram tissue(%ID/g)of different organs.Results ①The labeling efficiency of ¹⁸⁸Re-IGF-1A was(94.07±0.32)%.②The largest uptake of tumors was(42.38+17.82)%ID/g at 4 h after injection of ¹⁸⁸Re-IGF-1A.Then the tumor to normal tissue ratios increased and the largest Rnnor to mugcle ratio was 6531.79±4930.26 at 5 d after injection.③¹⁸⁸ReO₄^- wag major distributed in thyroid glands,stomachs,tumors and blood in nude mice after injection at first.Then%ID/g decreased rapidly in tumors.④The difference of%ID/g wag siguificant(t=5.877,t=13.287,P<0.01) in tumors and kidneys between ¹⁸⁸Re-IGF-1A group than in ¹⁸⁸ReO₄^- group.The largest ratio of tumors in the two groups was 74.10 at 24 h after injection.⑤After being injected,¹⁸⁸Re-IGF-1A formed clear images in tumom.5 d later,nothing but tumors can be seen.Conclusions ¹⁸⁸Re-IGF-1A has good affinity with human pancreatic cancer,and the tumor to muscle ratios in nude mice is high.So ¹⁸⁸Re-IGF-1A is expected to be used for targeting therapy of human pancreatic carcinoma.