To be used as a carrier of ⁶⁸Ga radioisotope for possible blood pool imaging studies, dialdehyde dextran thiosemicarbazone (DADTSC) Schiff base polymer with different thiosemicarbazone contents (TSCC) = 0.93, 2.43, and 3.4 mmol/g were synthesized and characterized by FT-IR, GPC, and CHNS. Although they were successfully radiolabeled at room temperature, stable radio-complexes were prepared at 60 °C. Effect of thiosemicarbazone content on the dissolution rate, cytotoxicity, coagulation and hemolysis activities, and radiolabeling efficiency of Schiff bases as well as on the in-vitro radio-complexes stability was investigated. DADTSC1 (TSCC = 0.93 mmol/g) showed a less cytotoxicity (cell viability, CV₅₀ = 490 μg/ml), a better solubility, suitable coagulation and hemolytic activities, and a sufficient radiolabeling efficiency (Radiochemical purity (RCP) > 95%) and formed a stable (RCP > 90%) radio-complex, which be chosen for in-vivo biodistribution study in healthy rats through tissue sampling and counting for radioactivity. Like blood pool imaging agents, ⁶⁸Ga-DADTSC1 presented a retention profile in blood circulation, though more studies, including imaging in larger mammals, are required.