Transarterial radioembolization (TARE) is a treatment method for liver tumours, during which radioactive microspheres are injected in the hepatic artery (HA) via a microcatheter. The HA blood flow will transport the microspheres predominantly towards the hepatic arterioles supplying the tumours. This technique relies on the liver’s unique dual blood supply, where tumour tissue is primarily supplied by the HA, while normal liver parenchyma receives most of its blood supply via the portal vein (PV). At the time this research was conducted, three types of microspheres were commercially available: two incorporating the radionuclide yttrium-90 and one containing holmium-166. This thesis concentrates on holmium microspheres, which offer unique imaging capabilities, particularly enabling quantitative analysis through MRI. In terms of size, density, and clinically administered quantities, holmium microspheres are very similar to yttrium resin microspheres. 
Therefore, the results presented here are likely to be applicable to yttrium resin microspheres as well. Maximizing microsphere delivery to tumorous tissue while sparing healthy liver tissue – achieving a high tumour to non-tumour (T/N) ratio – is very important for TARE efficacy. Achieving this requires control over microsphere distribution, potentially through adjusting treatment parameters, such as microsphere injection technique.
This PhD project investigated which parameters influence the microsphere distribution during TARE using in vitro and ex vivo experiments, to contribute in the development of patient-specific treatment plans for TARE.