Figure 1: (a) Schematic illustration showing the possible mechanism for radionuclides or drug accumulation delivery system of nanoparticles by site specific passive tumor targeting using the enhanced permeability and retention (EPR) effect or molecular affinity and site specific active tumor targeting through ligand tumor cell surface receptors interaction, internalization, and intracellular action for tumor diagnostics and therapy (reproduced with modification with permission from [7]). (b) Schematic diagram of tumor tissue penetration range of internal radiotherapy by auger electron (0.1–2 keV, < 1  𝜇 m )-, 𝛼 (5–8 MeV, 50–80  𝜇 m range)-, and 𝛽 (0.1–2.2 MeV, 1–10 mm range )- radiation emitters for passively and actively nanotargeted radionuclide therapy (reproduced with modification with permission from [14]).