Ionic characteristics and osmolarity of cooling fluid in hepatic laser ablation: a 7T MRI-based comparison in ex vivo bovine liver

To compare MRI-defined ablation volume among three cooling fluids with different ionic characteristics and osmolarity in ex vivo bovine liver tissue. In this ex vivo pilot study, 36 laser ablations were performed in five bovine livers using internal applicator cooling with 0.9% sodium chloride, 5% dextrose in water, or 10% mannitol at 60 mL/h. Post-ablation MRI was performed at 7 T. Primary endpoint was manual MRI volumetry; secondary endpoint was maximum axial diameter. Semi-automatic volumetry and intra-rater repeatability were assessed as supplementary analyses. Linear mixed-effects models with source liver as a random intercept were used for group comparisons. Overall, 33/36 ablations were evaluable. Mean ablation volume was 21.4 ± 1.5 cm³ with sodium chloride, 21.7 ± 1.4 cm³ with dextrose, and 23.6 ± 1.3 cm³ with mannitol. Cooling fluid group was associated with ablation volume (p = 0.002). Ablation volume was larger with mannitol than with sodium chloride (mean difference, 2.2 cm³; adjusted p < 0.001) or 5% dextrose (mean difference, 1.9 cm³; adjusted p = 0.006). Maximum axial diameter showed the same group pattern. Agreement between manual and semi-automatic volumetry was high (ICC, 0.96); intra-rater repeatability was excellent for volume (ICC, 0.98) and diameter (ICC, 0.97). In ex vivo bovine liver, 10% mannitol was associated with larger MRI-defined laser ablation volumes than 0.9% sodium chloride or 5% dextrose.