Caren van Roekel

225 The efficacy of coil-embolization in radioembolization What this study adds to the existing literature is the quantitative analysis to evaluate the actual microsphere distribution post-treatment, and the use of 90 Y-PET/CT instead of 90 Y-Bremsstrahlung-SPECT as it offers better spatial resolution and contrast for optimized quantification of 90 Y-activity (11,12). The study had several limitations that were mainly related to the quantitative analyses. Registration errors occurred when fusing the CECT and the post-treatment images, especially in patients with multiple small bilobar tumors. Furthermore, errors were introduced due to manual segmentation, heterogeneity due to the use of multiple microsphere types, and the use of two different post-treatment imaging modalities (i.e. 90 Y-PET/CT and 166 Ho-SPECT/ CT). Lastly, the study was limited by its retrospective nature as well as small sample size. Based on the results of this study we recommend using the redistribution technique only when deemed absolutely necessary. The best results are achieved in coil-embolization of the segment IV artery. Coil-embolization of parasitized arteries showed the least favorable redistribution of microspheres, caution is therefore advised in the treatment of hypervascular tumors. In conclusion, visual evaluation of post-treatment imaging tends to overestimate the effect of redistribution. Quantitative analysis demonstrated significantly lower absorbed doses in redistributed dependent parts of the liver. 8