Labeling and preliminary in vivo assessment of niobium-labeled radioactive species: A proof-of-concept study by Radchenko, V, Bouziotis, P, Tsotakos, T, Paravatou-Petsotas, M, la Fuente, A, Loudos, G, Harris, A, Xanthopoulos, S, Filosofov, D, Hauser, H, Eisenhut, M, Ponsard, B, Roesch, F