INFLUENCE OF QUANTITATIVE CHARACTERISTICS ON MRI-GUIDED FOCUSED ULTRASOUND ABLATION OF UTERINE FIBROIDS: THE POTENTIAL USE OF SIGNAL INTENSITY VALUES FROM FIBROID IN T2-WI AS A CRITERION FOR PATIENT SELECTION

Objective. To determine the effect of quantitative characteristics on the effectiveness of magnetic resonance imaging guided focused ultrasound (MRIgFUS) ablation of uterine fibroids and evaluate the possibility of their use for patient selection.

Material and methods. Retrospective analysis of 67 FUS ablations (67 women, 94 fibroids) was performed. We evaluated the characteristics of fibroids (standardized signal intensity (SSI) and signal heterogeneity in T2-WI, the maximum diameter, the distance to the skin and to the sacrum during FUS, volume, nonperfused volume (NPV), MR-type), sonication energy and patients age. Standardization of the fibroid signal intensity was performed by using the signal intensity from iliac muscle. Correlation between NPV and quantitative characteristics was calculated. ROC-analysis was performed for determination of the optimal SSI threshold value required to achieve NPV≥50%. We evaluated the relation between MR-type of fibroids, NPV ratio and SSI.

Results. Post treatment NPV ratio was 57.1 ± 22.5%. NPV for 1 type fibroids (n=67) was 63.4 ± 19.7%, for 2 type (n=20) – 46.8 ± ± 19.5% and for 3 type (n=7) – 26.4 ± 21%. Differences between
groups was significant (p<0.05). SSI showed significant correlation with NPV ratio (R=-0.28, p<0.01). Significant correlation between NPV ratio and others quantitative characteristics was not detected. Fibroids with SSI≤1.4 characterized NPV≥50% (sensitivity 72.7%, specificity 71.4%, p<0.01, AUC 0.72). MR-types of fibroids were characterized by different SSI (p<0.05). SSI≤ 1/4 was characteristic only for 1 type fibroids.

Conclusion. SSI can be used as an additional objective criterion for prediction of FUS results and patient selection. Good results of FUS (NPV≥50%) in most cases can be achieved for fibroids with SSI≤1.4.

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