Evaluation of the accuracy of peri-operative CEUS in measuring the effect of microwave ablation treatment of uterine fibroids, in comparison with MRI

OBJECTIVE: The objective of this study was to determine if peri-operative contrast enhanced ultrasound (CEUS) is as accurate as magnetic resonance imaging (MRI) in measuring the immediate effect of microwave ablation (MWA) treatment of uterine fibroids. Secondary outcomes were ablation ratio and proportion of recurrence of treated fibroids at 6 months. METHODS: The study was a prospective observational trial. Seventeen patients with symptomatic uterine fibroids were included and treated with percutaneous ultrasound guided microwave ablation. Before the ablation, the volume of the up to three largest fibroids were recorded with MRI and CEUS. At the end of operation, the ablated volume was recorded with CEUS and compared to MRI within a week. At 6 months, the ablated volume was again recorded with MRI and any sign of regrowth of the treated fibroid(s) was noted. RESULTS: A total of 19 fibroids were analyzed. The intraclass correlation coefficient (ICC) between ablation volume obtained by CEUS and MRI respectively was calculated to be 0.965 (95% confidence interval 0.909, 0.987). The Bland-Altman graph showed that the mean difference between volumes was -1.68 ml and standard deviation 22.60 ml, giving the limits of agreement (-45.98, 42.61). Regrowth of vascularized tissue was seen in 8 fibroids (47%). CONCLUSION: CEUS can be used to evaluate ablation volume and ablation ratio and is useful for intraoperative estimation and guidance. It shows strong correlation with MRI. Regrowth of fibroids may occur even when initial treatment was technically successful.