Caren van Roekel

267 Discussion Which imaging work-up procedures need to be performed before treatment with radioembolization? Before treatment with radioembolization, the first step in the selection process of a patient is imaging with 18 FDG-PET/CT. This is performed to assess the extent of a patient’s disease, especially to rule out the presence of significant extrahepatic disease. It was shown that 18 FDG-PET/CT showed significantly more extrahepatic disease than conventional CT, often leading to a change of management in patients who are candidates for radioembolization (66). Secondly, patients’ anatomy should be carefully evaluated on contrast-enhanced CT, using an early arterial phase. Van den Hoven et al. described that there are as many as sixteen different hepatic arterial segmental vascularization patterns (67). A timely assessment of the hepatic vascularity allows for personalized treatment planning with the definition of the number of injection positions, target volumes and activity calculation (67, 68). Depending on the primary tumor (in case of hepatocellular carcinoma (HCC), MRI is the imaging modality of choice), the contrast-enhanced CT or –MRI can be used for segmentation of the tumors and the healthy liver tissue. The (target) volumes obtained are used for activity calculation. To ensure patients’ safety, which is especially important in patients with HCC, who often have a cirrhotic liver, the distribution of the liver function can be determined using hepatobiliary scintigraphy. Currently, hepatobiliary scintigraphy is mostly used to assess the future liver remnant in patients scheduled for hepatic surgery. However, it can also be used in the work-up for radioembolization. Treatment may be adapted based on liver function distribution, e.g. choosing sequential lobar treatment instead of a whole-liver approach (57). Why is treatment with radioembolization preceded by a scout dose? Before treatment with radioembolization, a preparatory angiography with administration of a scout dose of either 99m Tc-MAA or 166 Ho-scout is performed. This is done for several reasons: to map the arterial anatomy, to assess the necessity of coil-embolization of arterial branches, to determine the optimal 10