Non-contrast enhanced MRI for assessment of uterine fibroids' early response to ultrasound-guided high-intensity focused ultrasound thermal ablation

Purpose: To examine non-contrast enhanced MRI value to evaluate necrotic area and ablation rate of uterine fibroids after high-intensity focused ultrasound (HIFU) thermal ablation. Method: In total, 508 patients with 598 fibroids who underwent HIFU treatment were enrolled. Contrast-enhanced MRI (CE-MRI) with diffusion-weighted imaging (DWI)were performed before treatment and within two days post-treatment. DWI signal performance of post-operative fibroids was observed; apparent diffusion coefficient (ADC) and DWI signal values pre- and post-operation were measured. The volume of post-operative DWI signal change area and post-contrast enhanced fibroid necrosis area were compared. Results: Average ADC and DWI signal values before HIFU treatment were higher than those post-operation; the difference was statistically significant before and after ablation (P < 0.05). After HIFU, 78.09 % (467 / 598) of DWI showed complete regular or irregular high-signal rings and 21.91 % (131 / 598) showed incomplete high-signal rings. No significant difference was noted between the complete high-signal ring volume on DWI and the non-enhanced volume (P > 0.05); however, this difference was statistically significant compared with the incomplete high-signal ring volume on DWI (P < 0.05). Two doctors had good agreements on evaluating the morphology of high-signal rings (kappa > 0.75, P < 0.05). Conclusions: Combined with pre-operative T2WI and post-operative DWI, non-contrast enhanced MRI can effectively evaluate ablation rate for most patients with uterine fibroids.