Prediction of non-perfusion volume ratio for uterine fibroids treated with ultrasound-guided high-intensity focused ultrasound based on MRI radiomics combined with clinical parameters

BACKGROUND

Prediction of non-perfusion volume ratio (NPVR) is critical in selecting patients with uterine fibroids who will potentially benefit from ultrasound-guided high-intensity focused ultrasound (HIFU) treatment, as it reduces the risk of treatment failure. The purpose of this study is to construct an optimal model for predicting NPVR based on T2-weighted magnetic resonance imaging (T2MRI) radiomics features combined with clinical parameters by machine learning.

MATERIALS AND METHODS

This retrospective study was conducted among 223 patients diagnosed with uterine fibroids from two centers. The patients from one center were allocated to a training cohort (n = 122) and an internal test cohort (n = 46), and the data from the other center (n = 55) was used as an external test cohort. The least absolute shrinkage and selection operator (LASSO) algorithm was employed for feature selection in the training cohort. The support vector machine (SVM) was adopted to construct a radiomics model, a clinical model, and a radiomics-clinical model for NPVR prediction, respectively. The area under the curve (AUC) and the decision curve analysis (DCA) were performed to evaluate the predictive validity and the clinical usefulness of the model, respectively.

RESULTS

A total of 851 radiomic features were extracted from T2MRI, of which seven radiomics features were screened for NPVR prediction-related radiomics features. The radiomics-clinical model combining radiomics features and clinical parameters showed the best predictive performance in both the internal (AUC = 0.824, 95% CI 0.693-0.954) and external (AUC = 0.773, 95% CI 0.647-0.902) test cohorts, and the DCA also suggested the radiomics-clinical model had the highest net benefit.

CONCLUSIONS

The radiomics-clinical model could be applied to the NPVR prediction of patients with uterine fibroids treated by HIFU to provide an objective and effective method for selecting potential patients who would benefit from the treatment mostly.

Intravoxel incoherent motion diffusion-weighted MRI for predicting the efficacy of high-intensity focused ultrasound ablation for uterine fibroids

Purpose

To evaluate the significance of magnetic resonance (MR) intravoxel incoherent motion diffusion-weighted imaging (IVIM-DWI) quantitative parameters in predicting early efficacy of high-intensity focused ultrasound (HIFU) ablation of uterine fibroids before treatment.

Method

64 patients with 89 uterine fibroids undergoing HIFU ablation (51 sufficient ablations and 38 insufficient ablations) were enrolled in the study and completed MR imaging and IVIM-DWI before treatment. The IVIM-DWI parameters, including D (diffusion coefficient), D* (pseudo-diffusion coefficient), f (perfusion fraction) and relative blood flow (rBF) were calculated. The logistic regression (LR) model was constructed to analyze the predictors of efficacy. The receiver operating characteristic (ROC) curve was drawn to assess the model's performance. A nomograph was constructed to visualize the model.

Results

The D value of the sufficient ablation group (931.0(851.5-987.4) × 10-6 mm2/s) was significantly lower than that of the insufficient ablation group (1052.7(1019.6-1158.7) × 10-6 mm2/s) (p<0.001). However, differences in D*, f, and rBF values between the groups were not significant (p>0.05). The LR model was constructed with D value, fibroid position, ventral skin distance, T2WI signal intensity, and contrast enhanced degree. The area under the ROC curve, specificity, and sensitivity of the model were 0.858 (95% confidence interval: 0.781, 0.935), 0.686, and 0.947. The nomogram and calibration curves confirmed that the model had excellent performance.

Conclusion

The IVIM-DWI quantitative parameters can be used to predict early effects of HIFU ablation on uterine fibroids. A high D value before treatment may indicate that the treatment will be less effective in the early stages.

Post treatment and 3 month contrast enhanced MRI findings following HIFU of submucosal fibroids: a retrospective study

PURPOSE

This study used contrast-enhanced MRI (CE-MRI) examination to assess the efficacy of high-intensity focused ultrasound (HIFU) for submucosal fibroids.

METHODS

A total of 81 submucosal fibroids, including 33 cases of type 1, 29 cases of type 2, and 19 cases of type 2-5, treated by HIFU were retrospectively reviewed. CE-MRI was performed in all cases immediately after HIFU, the non-perfused volume ratio (NPVR) and the degree of endometrial impairment were recorded. Thereafter, CE-MRI was repeated in all cases after three months, and the change of fibroid volume shrinkage rate (FVSR), NPVR and the degree of endometrial impairment were recorded.

RESULTS

The immediate NPVR was 86.4 ± 19.3% in type 1, 90.0 ± 13.3% in type 2 and 90.3 ± 7.2% in type 2-5. Among 81 fibroids, grades 0, 1, 2 and 3 endometrial impairments were observed in 38.3%, 16.1%, 14.8% and 30.9%, respectively. Three months later, NPVR was 68.0 ± 36.4% in type 1, 74.3 ± 27.7% in type 2 and 85.0 ± 16.1% in type 2-5. Grades 0, 1, 2 and 3 endometrial impairments were observed in 64.2%, 23.5%, 9.9% and 2.4%.FVSR was 49.0 ± 1.3% in type 1, 39.6 ± 1.7% in type 2 and 37.2 ± 2.1% in type 2-5. The FVSR in submucosal fibroid type 1 was superior to type 2 and type 2-5 (p < 0.05). The NPVR of submucosal fibroids in type 2-5 were higher than type 1 (p < 0.05) .There was no difference among different types of submucosal fibroids in endometrial impairment (p > 0.05) three months after HIFU.

CONCLUSIONS

At three months after HIFU, FVSR was better for submucosal fibroid type 1 than for type 2 and type 2-5. And there was no difference in endometrial impairment among the different types of submucosal fibroid groups.

Comparison of computer simulations and clinical treatment results of magnetic resonance guided focused ultrasound surgery (MRgFUS) of uterine fibroids

Purpose

Magnetic resonance‐guided focused ultrasound surgery (MRgFUS) can be used to noninvasively treat symptomatic uterine fibroids by heating with focused ultrasound sonications while monitoring the temperature with magnetic resonance (MR) thermometry. While prior studies have compared focused ultrasound simulations to clinical results, studies involving uterine fibroids remain scarce. In our study, we perform such a comparison to assess the suitability of simulations for treatment planning.

Methods

Sonications (N = 67) were simulated retrospectively using acoustic and thermal models based on the Rayleigh integral and Pennes bioheat equation followed by MR‐thermometry simulation in seven patients who underwent MRgFUS treatment for uterine fibroids. The spatial accuracy of simulated focus location was assessed by evaluating displacements of the centers of mass of the thermal dose distributions between simulated and treatment MR thermometry slices. Temperature–time curves and sizes of 240 equivalent minutes at 43°C (240EM₄₃) volumes between treatment and simulation were compared.

Results

The simulated focus location showed errors of 2.7 ± 4.1, −0.7 ± 2.0, and 1.3 ± 1.2 mm (mean ± SD) in the anterior–posterior, foot–head, and right–left directions for a fibroid absorption coefficient of 4.9 Np m^–1 MHz^–1 and perfusion parameter of 1.89 kg m^–3 s^–1. Linear regression of 240EM₄₃ volumes of 67 sonications of patient treatments and simulations utilizing these parameters yielded a slope of 1.04 and a correlation coefficient of 0.54. The temperature rise ratio of simulation to treatment near the end of sonication was 0.47 ± 0.22, 1.28 ± 0.60, and 1.49 ± 0.71 for 66 sonications simulated utilizing fibroid absorption coefficient of 1.2, 4.9, and 8.6 Np m^–1 MHz^–1, respectively, and the aforementioned perfusion value. The impact of perfusion on peak temperature rise is minimal between 1.89 and 10 kg m^–3 s^–1, but became more substantial when utilizing a value of 100 kg m^–3 s^–1.

Conclusions

The results of this study suggest that perfusion, while in some cases having a substantial impact on thermal dose volumes, has less impact than ultrasound absorption for predicting peak temperature elevation at least when using perfusion parameter values up to 10 kg m^–3 s^–1 for this particular array geometry, frequencies, and tissue target which is good for clinicians to be aware of. The results suggest that simulations show promise in treatment planning, particularly in terms of spatial accuracy. However, in order to use simulations to predict temperature rise due to a sonication, knowledge of the patient‐specific tissue parameters, in particular the absorption coefficient is important. Currently, spatially varying patient‐specific tissue parameter values are not available during treatment, so simulations can only be used for planning purposes to estimate sonication performance on average.

Nonenhanced MRI-based radiomics model for preoperative prediction of nonperfused volume ratio for high-intensity focused ultrasound ablation of uterine leiomyomas

OBJECTIVES

To develop and assess nonenhanced MRI-based radiomics model for the preoperative prediction of nonperfused volume (NPV) ratio of uterine leiomyomas after high-intensity focused ultrasound (HIFU) treatment.

METHODS

Two hundred and five patients with uterine leiomyomas treated by HIFU were enrolled and allocated to training (N =164) and testing cohorts (N = 41). Pyradiomics was used to extract radiomics features from T2-weighted images and apparent diffusion coefficient (ADC) map generated from diffusion-weighted imaging (DWI). The clinico-radiological model, radiomics model, and radiomics-clinical model which combined the selected radiomics features and clinical parameters were used to predict technical outcomes determined by NPV ratios where three classification groups were created (NPV ratio ≤ 50%, 50-80% or ≥ 80%). The receiver operating characteristic (ROC) curve, area under the curve (AUC), and calibration and decision curve analyses were performed to illustrate the prediction performance and clinical usefulness of model in the training and testing cohorts.

RESULTS

The multi-parametric MRI-based radiomics model outperformed T2-weighted imaging (T2WI)-based radiomics model, which achieved an average AUC of 0.769 (95% confidence interval [CI], 0.701-0.842), and showed satisfactory prediction performance for NPV ratio classification. The radiomics-clinical model demonstrated best prediction performance for HIFU treatment outcome, with an average AUC of 0.802 (95% CI, 0.796-0.850) and an accuracy of 0.762 (95% CI, 0.698-0.815) in the testing cohort, compared to the clinico-radiological and radiomics models. The decision curve also indicated favorable clinical usefulness of the radiomics-clinical model.

CONCLUSIONS

Nonenhanced MRI-based radiomics has potential in the preoperative prediction of NPV ratio for HIFU ablation of uterine leiomyomas.

Magnetic resonance imaging parameters in predicting the ablative efficiency of high-intensity focused ultrasound for uterine fibroids

OBJECTIVE

To evaluate the role of quantitative MRI parameters in predicting HIFU ablation results for uterine fibroids.

MATERIAL AND METHODS

A total of 245 patients with uterine fibroids who underwent HIFU treatment in Chongqing Haifu Hospital were reviewed retrospectively. The patients were divided into two groups according to the non-perfused volume (NPV) ratio which was either higher or lower than 80%. The MRI parameters were measured, and a logistical regression analysis was performed to investigate the potential predictors associated with the NPV ratio. Receiver operating characteristics (ROC) analysis was used to determine the cut off value for MRI parameters in predicting a high NPV ratio.

RESULTS

The subcutaneous fat thickness in the group of patients with an NPV ratio over 80% was significantly thinner than that in the group of patients with an NPV ratio less than 80% (15 mm versus 21 mm). The signal intensity ratio of fibroids to skeletal muscle on T2WI was significantly lower in the group of patients with an NPV ratio over 80% compared with the group with an NPV ratio lower than 80% (2.46 versus 3.23). The signal intensity ratio of fibroid to skeletal muscle correlated negatively with the NPV ratio and positively with the energy efficiency factor (EEF). The cut off value of signal intensity ratio of fibroid to muscle for predicting the NPV ratio over 80% is 3.045.

CONCLUSION

The signal intensity ratio of fibroid to skeletal muscle on T2WI can be used as a factor for predicting the effectiveness of HIFU ablation of uterine fibroids.

Feasibility of apparent diffusion coefficient in predicting the technical outcome of MR-guided high-intensity focused ultrasound treatment of uterine fibroids - a comparison with the Funaki classification

PURPOSE

To investigate the feasibility of using an apparent diffusion coefficient (ADC) classification in predicting the technical outcome of magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU) treatment of symptomatic uterine fibroids and to compare it to the Funaki classification.

MATERIALS AND METHODS

Forty-two patients with forty-eight uterine fibroids underwent diffusion-weighted imaging (DWI) before MRgHIFU treatment. The DW images were acquired with five different b-values. Correlations between ADC values and treatment parameters were assessed. Optimal ADC cutoff values were determined to predict technical outcomes, that is, nonperfused volume ratios (NPVr) such that three classification groups were created (NPVr of <30%, 30-80%, or >80%). Results were compared to the Funaki classification using receiver-operating-characteristic (ROC) curve analysis, with statistical significance being tested with the Chi-square test.

RESULTS

A statistically significant negative correlation (Spearman's ρ = -0.31, p-value < 0.05) was detected between ADC values and NPV ratios. ROC curve analysis indicated that optimal ADC cutoff values of 980 × 10^-6mm²/s (NPVr > 80%) and 1800 × 10^-6mm²/s (NPVr < 30%) made it possible to classify fibroids into three groups: ADC I (NPVr > 80%), ADC II (NPVr 30-80%) and ADC III (NPVr < 30%). Analysis of the whole model area under the curve resulted in values of 0.79 for the ADC classification (p-value = 0.0007) and 0.62 for the Funaki classification (p-value = 0.0527).

CONCLUSIONS

Lower ADC values prior to treatment correlate with higher NPV ratios. The ADC classification seems to be able to predict the NPV ratio and may even outperform the Funaki classification. Based on these results DWI and ADC maps should be included in the MRI screening protocol.

Uterine Myomas: Focused Ultrasound Surgery

Uterine fibroids are the most common neoplasm in women. These lesions may be associated with impaired fertility and adverse obstetric outcomes. Medical treatment, myomectomy, hysterectomy and uterine artery embolization have been employed for the management of uterine fibroids. Focused ultrasound surgery (FUS) is a relatively recent technique that relies on mechanical and thermal energy of ultrasound for the ablation of a target tissue under an imaging guidance, that can be either ultrasound (US-guided FUS, USgFUS) or magnetic resonance (MR-guided FUS, MRgFUS). Pre- and peri-menopausal women are potential candidates for treatment; however, individual criteria need to be evaluated in order to establish the eligibility for the procedure. FUS procedure can be performed in an outpatient setting; it is a safe and effective treatment that has demonstrated to reduce symptoms associated with uterine fibroids. The adverse event rate is 8.7% and only 0.2% of patients experiences major complications. Pregnancy is possible after the treatment, and no damage to the endometrium has been observed following FUS procedure.

MRI evaluation of endopelvic fascial swelling and analysis of influencing factors in patients with uterine fibroids after high-intensity focused ultrasound ablation

Purpose: To evaluate endopelvic fascial swelling in patients with uterine fibroids after high-intensity focused ultrasound (HIFU) ablation on magnetic resonance imaging (MRI) and investigate the factors that influence endopelvic fascial swelling.Methods: MRI and clinical data from 188 patients with uterine fibroids who were treated with HIFU were analyzed retrospectively. The patients were divided into a fascial swelling group and a non-swelling group, and the degree of swelling was graded. Fascial swelling was set as the dependent variable, and factors such as baseline characteristics and HIFU parameters, were set as the independent variables. The relationship between these variables and fascial swelling was analyzed by univariate and multivariate analyses. Correlations between the factors and the degree of fascial swelling were evaluated by Kruskal-Wallis test.Results: The univariate analysis revealed that the fibroid location, distance from the fibroid to the sacrum, sonication time, treatment time, treatment intensity, therapeutic dose (TD), and energy efficiency (EEF) all affected the endopelvic fascial swelling (p < 0.05). Subsequently, multivariate analysis showed that the distance from the fibroid to the sacrum was significantly correlated with fascial swelling (p < 0.05). Moreover, TD and sonication time were significantly positively correlated with the degree of fascial swelling (p < 0.05). The incidence of sacrococcygeal pain was significantly correlated with fascial swelling (p < 0.05).Conclusion: The distance from the fibroid to the sacrum was a protective factor for fascial swelling. TD and sonication time were significantly positively correlated with the degree of fascial swelling.

Magnetic Resonance Imaging Parameters in Predicting the Treatment Outcome of High-intensity Focused Ultrasound Ablation of Uterine Fibroids With an Immediate Nonperfused Volume Ratio of at Least 90

RATIONALE AND OBJECTIVES

We aimed to investigate the role of magnetic resonance imaging parameters in predicting the treatment outcome of high-intensity focused ultrasound (HIFU) ablation of uterine fibroids with a nonperfused volume (NPV) ratio of at least 90%.

MATERIAL AND METHODS

A total of 120 women who underwent HIFU treatment were divided into groups 1 (n = 72) and 2 (n = 48), comprising patients with an NPV ratio of at least 90% and less than 90%, respectively. Multivariate logistic regression analyses were carried out to investigate the potential predictors of the NPV ratio of at least 90%. The NPV ratios immediately post-treatment, therapeutic efficacy at 6 months' follow-up, and safety in terms of adverse effects and changes in anti-Mullerian hormone level were assessed.

RESULTS

By introducing multiple predictors obtained from multivariate analyses into a generalized estimating equation model, the results showed that the thickness of the subcutaneous fat layer in the anterior abdominal wall, peak enhancement of fibroid, time to peak of fibroid, and the ratio of area under the curve of fibroid to myometrium were statistically significant, except T2 signal intensity ratio of fibroid to myometrium, hence predicting an NPV ratio of at least 90%. No serious adverse effects and no significant difference between the anti-Mullerian hormone levels before or 6 months post-treatment were reported.

CONCLUSIONS

The findings in this study suggest that the achievement of NPV ratio of at least 90% in magnetic resonance imaging-guided HIFU treatment of uterine fibroids based on prediction model appears clinically possible without compromising the safety of patients.

Tissue characterization of uterine fibroids with an intravoxel incoherent motion model: The need for T2 correction

BACKGROUND

Diminished signal intensity of uterine fibroids in T₂ -weighted images is routinely used as a qualitative marker of fibroid hypoperfusion. However, quantitative classification of fibroid perfusion with intravoxel incoherent motion (IVIM) model-based metrics is not yet clinically accepted.

PURPOSE

To investigate the influence of T₂ correction on the estimation of IVIM model parameters for characterizing uterine fibroid tissue.

STUDY TYPE

Prospective.

POPULATION

Fourteen women with 41 fibroids (12 Type I and 29 Type II, per Funaki classification) underwent diffusion-weighted imaging and T₂ mapping.

FIELD STRENGTH

Diffusion-weighted images (b values: 0, 20, 40, 60, 100, 200, 400, 600, 800, 1000 s/mm² ) and T₂ maps were obtained at 1.5T.

ASSESSMENT

The effect of uterine fibroid T₂ variation on IVIM model parameters (diffusion coefficient, perfusion coefficient, and perfusion volume fraction) were numerically modeled and experimentally evaluated without (D, D*, f) and with (D_c , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msubsup><mml:mi>D</mml:mi> <mml:mi>c</mml:mi> <mml:mo>*</mml:mo></mml:msubsup> </mml:mrow> </mml:math> , f_c ) T₂ correction. The relationship of T₂ with D and the T₂ -corrected perfusion volume fraction (f_c ) was also examined.

STATISTICAL TEST

D-values and f-values estimated with and without T₂ correction were compared by using a two-tailed Student's t-test.

RESULTS

Type II fibroids had higher D and f than Type I fibroids, but the differences were not significant (Type I vs. Type II, D: 0.83 ± 0.20 vs. 0.80 ± 0.25 mm² /s, P = 0.78; f: 23.64 ± 4.87% vs. 25.27 ± 7.46%, P = 0.49). For Type I and Type II fibroids, f_c was lower than f, and f_c of Type II fibroids was significantly higher than that of Type I fibroids (Type I vs. Type II, f_c : 7.80 ± 1.88% vs. 11.82 ± 4.13%, P = 0.003). Both D and f_c exponentially increased with the increase of fibroid T₂ as functions: <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mi>D</mml:mi> <mml:mi>c</mml:mi></mml:msub> <mml:mrow><mml:mo>(</mml:mo> <mml:mrow><mml:msub><mml:mi>T</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> <mml:mo>)</mml:mo></mml:mrow> <mml:mo>=</mml:mo> <mml:mo>-</mml:mo> <mml:mn>1.52</mml:mn> <mml:mo>×</mml:mo> <mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>3</mml:mn></mml:mrow> </mml:msup> <mml:mo>⋅</mml:mo> <mml:msup><mml:mi>e</mml:mi> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>3.42</mml:mn> <mml:mfrac> <mml:mrow><mml:msub><mml:mi>T</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> <mml:mrow><mml:mn>290</mml:mn></mml:mrow> </mml:mfrac> </mml:mrow> </mml:msup> <mml:mo>+</mml:mo> <mml:mn>1.84</mml:mn> <mml:mo>×</mml:mo> <mml:msup><mml:mrow><mml:mn>10</mml:mn></mml:mrow> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>3</mml:mn></mml:mrow> </mml:msup> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow><mml:msub><mml:mi>f</mml:mi> <mml:mi>c</mml:mi></mml:msub> <mml:mrow><mml:mo>(</mml:mo> <mml:mrow><mml:msub><mml:mi>T</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> <mml:mo>)</mml:mo></mml:mrow> <mml:mo>=</mml:mo> <mml:mo>-</mml:mo> <mml:mn>0.2336</mml:mn> <mml:mo>⋅</mml:mo> <mml:msup><mml:mi>e</mml:mi> <mml:mrow><mml:mo>-</mml:mo> <mml:mn>3.217</mml:mn> <mml:mfrac> <mml:mrow><mml:msub><mml:mi>T</mml:mi> <mml:mn>2</mml:mn></mml:msub> </mml:mrow> <mml:mrow><mml:mn>290</mml:mn></mml:mrow> </mml:mfrac> </mml:mrow> </mml:msup> <mml:mo>+</mml:mo> <mml:mn>0.2269</mml:mn> <mml:mo>,</mml:mo></mml:mrow> </mml:math> respectively. D asymptotically approached 1.79 × 10^-3 mm² /s, and f_c approached 21.74%.

DATA CONCLUSION

T₂ correction is important when using IVIM-based models to characterize uterine fibroid tissue.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;48:994-1001.

Clinical application of high-intensity focused ultrasound ablation for uterine fibroids

HIFU (high-intensity focused ultrasound) ablation is an emerging therapeutic modality that induces thermal coagulative necrosis of biological tissues by focusing high-energy ultrasound waves onto one small spot. This technique is at various stages of clinical applications in several organs. However, it has increasingly been used in the treatment of symptomatic uterine fibroids, a common condition affecting women. Since its first clinical use for symptomatic uterine fibroids, this technique has been recognized for safety, satisfactory therapeutic efficacy in symptom control, uterus-preserving ability, radiation-free nature, and because of the fact that it does not require hospitalization. Owing to its numerous benefits, HIFU ablation is currently one of the major therapeutic options for symptomatic uterine fibroids. In this review, several aspects ranging from the physical principle of HIFU to the long-term outcomes are summarized from the perspective of the clinical application for uterine fibroids.