Cancer is one of the leading causes of death in the world. Because of this, there are many novel methods to treat it being currently researched. One of the answers from the nuclear medicine perspective is Radionuclide Therapy, where alpha or beta emitters are applied, with the goal to selectively irradiate tumours in the body. A promising radionuclide researched for Radionuclide Therapy is Holmium-166, which is a beta emitter with a short half-life of 26.8 hours, which is useful for the treatment of large metastases. A method to ensure an effective treatment with Holmium-166 is the use of a Dysprosium-166/Holmium-166 in vivo generator, as the dose delivered to patients per administered dose is two times higher with the in vivo generator rather than the direct use of Holmium-166. However, carriers used in Radionuclide Therapy, which usually involve the formation of a chelator-metal complex are not effective for the in vivo generator due to the release of auger electrons during the decay process leading to the destruction of the chelator-metal complex. A promising non-chelator method designed by Liu et al. at the Applied Radiation and Isotopes research team at TU Delft involves the radiolabelling of micelles. This thesis sought to evaluate the use of micelles, radiolabelled with this mechanism as an effective carrier for the Dysprosium-166/Holmium-166 in vivo generator. For this, micelles made of Polycaprolactone-block-Polyethylene Oxide and Polylactic Acidblock-Polyethylene oxide were evaluated based on the obtained radiolabelling efficiency and their stability when challenged with diethylenetriaminepentaacetic acid (DTPA). The results in this study show that the radiolabelling method used to encapsulate Dysprosium relies on the diffusion of Dysprosium hydroxides into the micelle core, followed by precipitation as the right concentration is reached inside the micelles. The best results obtained by this study occur when radiolabelling Polylactic Acid-block-Polyethylene Oxide (PLA-PEO) micelles, and then adding phosphate ions at a concentration of 3 × 10−8𝑀, 30 minutes after the addition of the active Dysprosium. Although more tuning is required on the radiolabelling mechanism to make micelles the most effective carriers of the 166Dy/166Ho in vivo generator, promising first steps were made to begin this process ... Read more