Establishment Of A Scoring System For Predicting The Difficulty Level Of High-intensity Focused Ultrasound Ablation Of Uterine Fibroids

Uterine fibroids,occurring in 20-40% of women during reproductive age,are the most common benign tumors of female reproductive system.Although hysterectomy and myomectomy have been the standard treatments,technological revolutions have catalyzed a shift from open surgery towards minimally invasive or noninvasive treatment.Over the last decade,high intensity focused ultrasound（HIFU）has succeeded in delivering the ultimate objective truly non-invasive ablation.This non-invasive technique is becoming more widely applied in clinical practice due to its advantages of the low risk for complications,short recovery time,no radiation exposure,no surgical incision,and no damage to ovarian function.HIFU has the ability to yield coagulative necrosis at a precise focal point within target lesions while not affecting any surrounding structures.Previous studies have shown that uterine fibroids dispiaying hyperintensity on T2-weighted imaging（T2WI）or on T1 weighted images（T1WI）with significant enhancement are difficult to treat using HIFU.Several studies have also demonstrated that besides the blood supply of uterine fibroids and tissue structure of fibroids,different tissue thicknesses in the acoustic pathway and the size of fibroids are also important factors influencing the energy efficiency factor（EEF）,which is considered asthe quantitative index of energy delivery.To the best of our knowledge,no study has established a scoring system for predicting the difficulty level of HIFU ablation of uterine fibroids.Therefore,this retrospective study with a large number of subjects will first evaluate the relationship between ablation effects and the predict factors,then quantify the predictors to establish a scoring system for predicting the difficulty level of HIFU ablation of uterine fibroids.Objectives:（1）To establish a scoring system that predicts the difficulty level of high-intensity focused ultrasound（HIFU）ablation of uterine fibroids.（2）To verify a scoring system that predicts the difficulty level of HIFU ablation of uterine fibroids.Materials and Methods:（1）Four hundred and twenty-two patients with fibroids were enrolled.EEF and sonication time were set as dependent variables,with factors possibly affecting EEF and sonication time including age,body mass index,the volume of fibroids,the location of the uterus,the type of uterine fibroids,the signal intensity on T2 weighted imaging（T2WI）,the enhancement type,the thickness of the rectus abdominis and the subcutaneous fat layer,the distance from the anterior/ posterior surface of the fibroid to the skin,and the abdominal wall scar were set as predictors for building optimal scaling regression modes.（2）56 patients with fibroids from Chongqing Haifu Hospital were enrolled undergo ultrasound-guided high-intensity focused ultrasound treatment.The quantization of the value from MRI into the equations By comparing the prediction value from the equations and the true value,we can verify the prediction efficiency of the scale regression equation.Results:（1）The volume of fibroids,location of the uterus,the signal intensity on T2 WI,enhancement type,rectus abdominis thickness,subcutaneous fat thickness,and distance from the anterior surface of fibroid to the skin were related to EEF.Signal intensity on T2 WI,the volume of fibroids,distance from the posterior surface of fibroid to the skin,and enhancement type were related to sonication time.Models that can predict the difficulty level of HIFU for fibroids have been established: for EEF,y′ =0.338X’₁-0.231X’₂+0.156X’₃+0.167X’₄;for sonication time,y=0.227X₁+ 0.321X₂+0.157X₃+ 0.194X₄.（2）The correlation coefficient between the quantization predictor of EEF and EEF is predicted to be 0.574,and the correlation coefficient between the quantization predictor of sonication time and sonication time is 0.665,which shows the models that can predict the difficulty of ablation of uterine fibroids by ultrasound.Conclusion:A scoring system for predicting the difficulty level of HIFU treatment for uterine fibroids has been established and initially verified,it can be used to help select patients and to predict the sonication time for a given fibroid.