Female breast cancer is the second most common cancer worldwide. A promising novel technique to treat early-stage breast cancer is the use of thermo-brachy therapy. This thesis analysed the effect of the cancer biomarker glutathione (GSH) on the magnetic hyperthermal effects of iron oxide nanoparticles. The synthesised nanoparticles with a diameter of 10±4 nm have been coated with cysteine and treated with hydrogen peroxide leading to their aggregation upon cross-linking. As the GSH concentration is higher around cancerous cells (10 μM instead of 3 μM), these nanoparticles would be more monodispersed as GSH could break the disulfide bonds between the cysteines. Since aggregated nanoparticles exhibit lower heating efficiencies, it was assumed that this method would allow for (partially) selective heating of the tumour. The addition of 10 μM GSH resulted in an 11% higher heating efficiency compared to 3 μM GSH when analysing the coated nanoparticles in an alternating magnetic field. However, a GSH concentration of 10 mM (intracellular GSH concentration in cancerous cells) gave a decrease in heating efficiency. Another methodology was proposed as well. Uncoated nanoparticles were encapsulated in a ZIF-8 framework. This framework is less stable in environments with a lower pH value and higher GSH concentration, which is the case in the tumour microenvironment. This methodology gave a 27% higher heating efficiency in a tumour-related GSH concentration and pH value. The differences with both the cysteine and ZIF-8-based methods are yet too small to limit thermal damage to healthy tissue. Modelling the diffusion and its influence on the temperature change, gave very local heating near the injection site due to slow diffusion. Therefore, while this thesis provided insights into the heating efficiencies in tumour-related conditions with both methodologies, addressing the current limitations can lead to significant advancements.

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

166Ho is a promising radionuclide for targeted radionuclide therapy, because of its beneficial decay characteristics and the possibility to track its dose delivery in a patient. However, a problem for the use of 166Ho in these treatments is its limited maximally produced specific activity in neutron irradiation of a pure 165Ho target, since the produced 166Ho is chemically inseparable from the 165Ho target. The Szilard-Chalmers method is known to be able to increase the achieved specific activity. It does so by irradiating the target isotope while it is incorporated in a compound. As the target isotope undergoes (n, γ) neutron capture it forms the product isotope and escapes the compound due to recoil from prompt gamma emissions. Then by separating the product isotopes from the compound, which still contains the target isotopes, a high specific activity can be achieved. However, batch irradiations using the Szilard-Chalmers method for production of high specific activity gives low production yields. In order to increase these production yields, a continuous flow Szilard-Chalmers system is proposed. The objective of this research is to investigate the main processes at play in a continuous flow system using the Szilard-Chalmers method on 165HoDOTAfor the production of high specific activity 166Ho. Investigations on the labelling of Ho3+ to DOTA4- have shown that 96±3 % labelling efficiency is achievable. Experiments on relabelling and isotope-exchange have shown that less than 8 % of 166Ho3+ undergoes relabelling with DOTA4- or isotope-exchange with 165HoDOTA-. Also, a cation exchange separation method for separation of Ho3+ from DOTA4- and HoDOTA- was developed. Moreover, investigations on Szilard-Chalmers separation of a dried 165HoDOTAsample have shown that with a 4-minute irradiation it was possible to achieve a specific activity of 2.8±0.2 MBq mg-1 . This corresponds to an enrichment factor of 1.62±0.03 compared to an irradiation without Szilard-Chalmers separation. Decreased radiolysis by shielding and slowed neutrons, and increased initial labelling are expected to be able to increase the achieved enrichment factor even more. The continuous flow Szilard-Chalmers system could in potential prove very useful in high specific activity radionuclide production, but further improvements on its subprocesses are necessary before practical implication is worthwhile.

Breast cancer is one of the most dangerous forms of cancer worldwide. Continuous research is therefore essential in order to find realistic treatment options. 3D tumor spheroids have been proven to imitate the structural and physiological TME of in vivo tumors relatively more accurate than the more widely used 2D cell cultures.
During this study, the aim was to find the optimal conditions for single spheroid formation, employing breast cancer cells and utilizing GrowDex. Different concentrations and cell densities were used, as
well as differing methods (GrowDex addition prior or (days) after cell cluster formation). The liquid overlay technique was used to grow the spheroids, which were observed for a maximum of 14-16 days. Finally, an ATP viability assay was performed to determine whether the spheroids contained a proliferation zone, which corresponds to active cells.
Single spheroids were obtained for all cell densities. The relatively high GrowDex concentrations responded well to a cell density of 2000 cells, while the relatively low GrowDex concentrations responded well to cell densities of 5000 and 10000 cells. Through the ATP viability assay the samples illustrated
the presence of a proliferation zone, and thus active cells.

Treatment of early stage breast cancer is generally invasive to a patient's daily life while being treated. Therefore, to diminish the physical and psychological impact during and after recovery, a newly proposed minimally invasive therapy for early-stage breast cancer treatment is proposed. Within this study, this proposed treatment is modelled to gain more knowledge of the behavior of the treatment material in tissue. The treatment includes magnetic thermal ablation, which is combined with permanent Low Dose Rate (LDR) brachytherapy, both performed simultaneously.
The goal of the treatment is to diminish the physical and psychological impact during treatment and after recovery, since it requires only a single medical intervention. The treatment material consists of radioactive palladium-103 superparamagnetic iron-oxide nanoparticles (Pd-103 SPIONs) incorporated in a solid gel, forming a seed that is implanted into the tumor. To investigate the effectiveness and limitations of the combined therapy, computational simulations were performed in Matlab using the Finite Element Method (FEM).
These simulations allowed for the prediction of the treatment results, by calculating the temperature distribution based on Pennes' bioheat equation, the nanoparticle concentration distribution and the dose distribution over time. The sensitivity of the results to the relevant physical properties and optimization parameters was analyzed. The latter resulted in a recommended optimization approach that ultimately could be used for treatment planning. First, an initial simulation was performed using property values from literature. Then, the temperature and dose results were tested on their sensitivity to model parameter changes. The temperature model was found to be most sensitive to changes in the nanoparticle heat source value Qnp, to an increased heat conduction coefficient k and to a decreased blood perfusion rate wb. The cumulative dose results are sensitive to both the initial concentration ci and to a decreased diffusion coefficient D. It is concluded that accurate values for these temperature and concentration model parameters are necessary to perform relevant simulations.
Furthermore, the possible optimization parameters were identified. For dose optimization, these parameters are the activity of the nanoparticles A, which is not easily modified, and the initial nanoparticle concentration in the seeds ci, which affects the temperature distribution as well. The temperature distribution specific variables that were found, are the strength of the magnetic field H and the time t of magnetic field application, which both can be adjusted during the treatment. The seed location and number of seeds are two additional adjustable variables used for optimization of both temperature and dose distribution. Lastly, it was concluded that the internal radiation part of the treatment is limiting in the reaching treatment goals and in number of optimization possibilities, compared to the thermal ablation part. Therefore, treatment optimization should be performed on the dose distribution first. Because most limitations of the models are a result of the 2D representation and because these limitations strongly affect the outcomes of the models, it is recommended to transform these models to 3D. These limitations make it impossible to do proper treatment planning with the 2D model, which requires a 3D view of the results. With all these findings, this study has contributed by providing basic knowledge of the state-of-the-art early stage breast cancer combined therapy, bringing it one step closer to clinical implementation.

Calcium is an important nutrient for both young and elderly people which can, among others, stimulate healthy bone growth and prevent osteoporosis. Therefore, nutrition with sufficient calcium is of great importance. The highest calcium nutrient density for all foods can be found in bovine milk, which contains on average 1.2 g Ca / L. To increase the amount of bioavailable calcium, milk can be fortified by the addition of different calcium salts. In this research the bioavailability and exchangeability of calcium in unfortified and fortified skimmed milk was studied by in vitro methods using equilibrium dialysis and ultracentrifugation to separate different fractions in milk. Radioactive 45Ca was used to follow the exchange behaviour of calcium between the three different fractions in milk: casein micelles, serum proteins, and soluble calcium. For unfortified milk it was found that 34.9 ± 2.2% of the calcium was present in the soluble phase, 9.1 ± 0.6% was bound to serum proteins, and 56 ± 1.6% was present in the casein micelles, which confirmed the results in literature. In addition, with the investigation of the exchange behaviour of 45Ca, it was confirmed that ~40% of calcium in casein micelles is hardly exchanged.To investigate the influence of calcium fortification on the calcium equilibrium in milk, six different calcium salts were selected to be synthesized: calcium chloride, calcium carbonate, calciumgluconate, tri-calcium di-citrate, calcium lactate, and tri-calcium phosphate. Of these, calcium chloride, calcium carbonate, calcium gluconate, and tri-calcium di-citrate were successfully synthesized. Further experiments were performed with calcium chloride and calcium carbonate, intrinsically labelled with 45Ca. From fractionation with ultracentrifugation, it was concluded that addition of calcium chloride led to an increase of calcium in the soluble phase, which might indicate an increase in bioavailability. Fortification of milk with 45Ca labelled calciumcarbonate did not lead to an exchange of 45Ca with the calcium present in milk, indicating that calcium carbonate is unlikely to make calcium in milk more bioavailable. In conclusion, a better understanding of the solubility and exchangeability of Ca in milk and the influence of milk fortification with calcium chloride and calcium carbonate is obtained by using 45Ca as a tracer.

Treatment of cancer requires local medication at the tumor site to prevent side-effects of chemotherapy. Nanocarriers, such as micelles, can be used to transport drugs to the tumor site and limit side effects of cancer treatment. Micelles are easy to produce, have a high solubilization potential for hydrophobic drugs and therefore can have high loading capacity. Due to the increase in cell division and higher activity of cancer cells, elevated levels of reactive oxygen species (ROS) are often present at the tumor site. ROS have a highly oxidizing agent property by damaging DNA of cancer cells, it can be used to treat tumors. Beside ROS formation of the metabolic cycle, ROS can also be produced by ionizing radiation. With radiolysis of water, caused by radiation, the ROS concentrations at tumor sites can be increased. This research aimed to prepare micelles made from a block copolymer, that are sensitive to ROS and that are sensitive to ROS formed by radiolysis of water with gamma radiation for drug release purposes. 4-(methylthio)phenyl acrylate (MTPA) groups present in the block copolymer (PDMA-MTPA), are sensitive for oxidation reactions which will lead to decomposition of the polymer, and thus of the micelles. During this research, micelles with a hydrodynamic diameter between 30 and 50 nm were exposed to H2O2 levels between 2 wt% (0.6 M) and 0.007 wt% (2 mM) and a change in hydrodynamic diameter and light intensity scattering was observed, meaning that micelles decompose with elevated concentrations of H2O2. In addition, an increase in hydrodynamic diameter was observed for micelles exposed to a dose between 67 and 500 Gray by irradiating with gamma rays of 1.25 MeV originating from a 60Co source, indicating that micelles cluster after sufficient dose of gamma radiation. These characteristics can be useful for making PDMA-MTPA micelles, a suitable candidate for drug delivery applications.

The goal of this research was to perform a 3D end-to-end test on a MR-linac to check the whole workflow using a clinical treatment plan. Dosimetric gel was used to obtain 3D spatial information, with the phantom in the same position for irradiation and scanning. In order to achieve this, fundamental elements of gel dosimetry needed to be investigated. In the MR-linac, irradiation is delivered in the presence of a permanent magnetic field. Therefore, the dosimetric response within a 1.5 T magnetic field should be validated. It is also important to investigate the time-dependence of the gel. It is preferable to read-out the gels within approximately one hour, so that the phantom does not have to be moved. Ideally, scanning and irradiation would be done at the same time, to see the dynamical dose delivery. The VIPAR gel was used for this research. The experiments demonstrated that R2 values for doses irradiated with magnetic field were the same as R2 values for the same dose irradiated without magnetic field. R2 values are still proportional to the dose. It was also shown that it is possible to scan the phantom within 20 minutes after irradiation. Sensitivity is at its highest after approximately 8 hours and stays stable afterwards, so scanning after 8 hours will improve the read-out accuracy. It was also possible to make a fit for the R2 versus time plots, which makes it possible to correct for change over time. The fit can be divided in two linear parts if time is plotted on a logarithmic scale, one fit for the time points before 7 hours, one for the time points after 7 hours. The partial doses acquired by the gel during radiation delivery were estimated. The equivalent R2 values then agreed with the extrapolated fit to within 4%. This is a good indication that dynamic gel (4D) dosimetry may be achievable. A protocol for a relative end-to-end test was also developed. From the preliminary results, it appeared that a relative end-to-end test can be performed with the read-out of gel within 1 hour. A new MR sequence needs to be developed. For this end-to-end test, the sequence needs to scan a larger volume with a higher resolution, therefore, the scan time will increase and real-time dosimetry will not be possible. Changing the MR sequence might also change the optimal irradiation-scanning interval and the R2 versus time curve. To perform absolute dosimetry, an extra calibration would be required.

Heat in thermal therapy can be produced by exposing superparamagnetic iron oxide nanoparticles (SPIONs) to alternating magnetic fields in order to treat cancer. In addition, Magnetic Resonance Imaging (MRI) uses SPIONs as T2 contrasts agents for diagnostic purposes. This attribute gives SPIONs potential to be used as theranostic agents in MRI – guided thermotherapy in order to visualize the concentration of the particles within the tumour and monitor the effect of the treatment. The performance of SPIONs as heating and contrast agents is highly dependent on their physical and magnetic properties. In this study, six different samples of palladium core superparamagnetic iron oxide nanoparticles (Pd – SPIONs), a formulation that has not been found in literature until today, synthesized at the Reactor Institute Delft were provided. The goal of this MSc Thesis was to determine the structural and magnetic particle parameters of Pd - SPIONs that were related with optimal heating and contrast enhancing performance in thermotherapy and MRI, respectively. For this purpose, all samples were fully characterized and their performances as heating and MRI contrast agents were investigated and compared along with commercial nanoparticles. In addition, MRI phantom and CT studies were performed using the commercial nanoparticles in order to determine whether quantification of different concentrations was possible.

Neutron capture therapy (NCT) is a binary form of radiotherapy that utilizes the high cross section of some nonradioactive elements, in particular boron-10 and gadolinium-157, for thermal neutron capture. The energetic charged particles (electrons and alpha particles) released in the capture reaction cause a high localized deposition. For almost a century, NCT has been regarded as the holy grail of targeted radiotherapy, but its superiority over other available treatments has not been demonstrated so far. Limitations included amongst others a poor and non-selective biodistribution of Boron carrier molecules, the limited availability of suitable neutron sources, a lack of tools for patient selection and individualized dosimetry, and a shortage of properly conducted clinical trials.