Caren van Roekel

24 Chapter 2 ablation (RFA) are hindered by the nearby large vessels, radioembolization is a good alternative for treatment of caudate lobe tumors (36). Van den Hoven et al. have described as many as sixteen different hepatic arterial segmental vascularization patterns, differing by the presence of accessory or replaced hepatic arteries, their respective vascular territory, and the origin of the artery vascularizing liver segment 4 (37). An accessory hepatic artery is an aberrant hepatic artery that vascularizes the left (segment 2) or right hemi-liver partially (any segments), existing in addition to a normally derived LHA and RHA. A replaced hepatic artery is an (aberrant) hepatic artery with a different origin (not the PHA) that vascularizes the left (segments 2-3 or segments 2-4) or right hemi-liver (segments 5-8). Timely assessment of the anatomy enables the establishment of a personalized treatment strategy ahead of time, including coil embolization of aberrant arteries, planning the number of injection positions and pretreatment activity calculation (37, 38). It is important to localize the segment 4 artery: it can be decided to use the segment 4 artery as a separate site of administration, include it in a more proximal injection position or coil-embolize it to induce intrahepatic redistribution of blood flow (39, 40). Knowledge of the location of the segment 4 artery can also be used in pretreatment activity calculation and avoidance of over- or underdosing of segment 4 (23). 3. PREPARATORY ANGIOGRAPHY AND INTRAPROCEDURAL IMAGING Before treatment, a preparatory angiography is performed for several reasons: [1] to map the arterial anatomy, [2] to assess the necessity of coil embolization of arterial branches, [3] to determine optimal catheter positioning and [4] to administer a simulation scout tracer. Traditionally, a transcutaneous transfemoral approach using the Seldinger technique was mostly used to gain intra-arterial access. Recently, there has been a rapid increase in the use of the radial artery as access site. Bishay et al. have found that the transradial approach is a safe and feasible access option for radioembolization and that it is associated with a low complication rate (41). After securing the access site, a pre-shaped catheter is used to enter the source of the hepatic arterial vasculature (usually the celiac axis). A standard end-