Caren van Roekel

220 Chapter 8 Time Interval A total of 28 patients were included in the time interval subgroup analysis. Fourteen of which had coil-embolization performed on the same day as the treatment procedure, while the comparison group had a median time interval of 10 days (2-32 days). Mean activity ratios in patients treated on the same day were higher than those in the comparison group. Respectively, 0.94 vs 0.80 in segment ratios and 0.72 vs 0.69 in tumor ratios, however the differences were not statistically significant (figure 4b). DISCUSSION This study aimed to evaluate the use of coil-embolization for inducing redistribution of hepatic blood flow in radioembolization, by qualitatively and quantitatively analyzing the post-treatment distribution of microspheres. Visual assessment of post-treatment imaging found that 70% of redistribution cases had a similar distribution of microspheres in the dependent and non- dependent segments. However, quantitative assessment demonstrated notably lower absorbed doses in both dependent tumors and segments, 71% of dependent tumors had an activity concentration that was ≥ 10% lower than their non-dependent counterparts. Several studies have previously reported on the redistribution method(4–8). Three studies visually assessed blood flow redistribution. Lauenstein et al. and Spreafico et al. examined the appearance of collaterals on DSA after coil- embolization, as well as the visual presence of 99m Tc-MAA or 90 Y-microspheres in the dependent segments (5,7). Redistribution of flow was found in 89% (24/27) and in 100% (n=17) of cases, respectively. Bilbao et al. assessed and scored the accumulation of 99m Tc-MAA in the dependent tumors (8). 99m Tc-MAA activity was visually present in 95% (23/24) of the dependent tumors. In 66% (16/24) of patients the distribution of 99m Tc-MAA in dependent tumors was considered similar to the non-dependent segments, which was in concordance with the findings of our visual assessment.