Development of Fibroblast Activation Protein-Targeted Radiotracers with Improved Tumor Retention. - Loktev A; Lindner T; Burger EM; Altmann A; Giesel F; Kratochwil C; Debus J; Marmé F; Jäger D; Mier W; Haberkorn U (Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 2019)