Objective To evaluate and compare the ability to detect tumor by bis (N-ethoxy-N-ethyl dithiocarbamato) nitrido99mTc(V) [99mTcN(NOEt)2] and99mTc hexakis-2- methoxyisobutyl isonitrile [99mTc-MIBI]. Methods 99mTcN(NOEt)2 was prepared and quality control was performed using ascending thin-layer chromatography. Four mice bearing Ehrich ascites tumor cells underwent whole body planar imaging at 30 min, 2 h and 4 h after injection of99mTc-MIBI or99mTcN(NOEt)2. ROIs were drawn around the tumor, head, chest, and contralateral limbs in whole body planar images, and ratios of radioactivity in tumor in head (T/H), chest (T/C), and contralateral limbs (T/L) were calculated. The mice of99mTcN (NOEt)2 group were killed, then blood was collected, and the tumor and organs were excised, weighed and the radioactivity was measured. Results 99mTcN(NOEt)2 was stable after 4h at the room temperature.99mTcN(NOEt)2 was delivered to the tumor selectively and efficiently.99mTcN(NOEt)2 was found to provide excellent tumor-to-nontumor contrast for all the tissue except the abdomen. The T/L ratios increased to their maximums (4.87) at 2 h after injection. There was significant difference between the99mTcN(NOEt)2 imaging group and99mTc-MIBI imaging group. In vitro the radioactivity ratios per unit weight of tumor to blood, muscle, skeleton, lung, heart, and spleen were much higher than those of tumor to liver, instestine. Conclusion In mice bearing Ehrich ascites tumor,99mTcN(NOEt)2 exhibits a set of features essential for a good tracer for tumor imaging, including a rapid washout from blood, high uptake rate in tumor tissue, prolonged retention and high tumor-to-nontumor uptake ratio. The imaging quality of99mTcN(NOEt)2 was superior to that of99mTc-MIBI. These features indicate that99mTcN(NOEt)2 may be a better tracer to detect tumor than99mTc-MIBI. Key words tumor - radionuclide imaging - NOEt - MIBI
