Ultrasound-guided percutaneous microwave ablation for symptomatic uterine fibroid treatment – A clinical study

Tissue Ablation: Applications and Perspectives

Tissue ablation techniques have emerged as a critical component of modern medical practice and biomedical research, offering versatile solutions for treating various diseases and disorders. Percutaneous ablation is minimally invasive and offers numerous advantages over traditional surgery, such as shorter recovery times, reduced hospital stays, and decreased healthcare costs. Intra-procedural imaging during ablation also allows precise visualization of the treated tissue while minimizing injury to the surrounding normal tissues, reducing the risk of complications. Here, the mechanisms of tissue ablation and innovative energy delivery systems are explored, highlighting recent advancements that have reshaped the landscape of clinical practice. Current clinical challenges related to tissue ablation are also discussed, underlining unmet clinical needs for more advanced material-based approaches to improve the delivery of energy and pharmacology-based therapeutics.

Application of transabdominal ultrasound- and laparoscopy-guided percutaneous microwave ablation for treating uterine fibroids: 24-month follow-up outcomes

PURPOSE

To determine the ablation efficacy of transabdominal ultrasound- and laparoscopy-guided percutaneous microwave ablation (PMWA), to investigate whether the risk of damage to adjacent organs and endometrium due to this technique can be reduced or even avoided. We also evaluated the clinical efficacy of this technique in the treatment of uterine fibroids of different sizes and at different locations over a 24-month follow-up period.

METHODS

This study included 50 patients with uterine fibroids who underwent transabdominal ultrasound- and laparoscopy-guided PMWA from August 2018 to July 2020. Lesions were confirmed by pathology. The technical efficacy and complications of PMWA were assessed. The lesion diameter, lesion volume, lesion location, and contrast-enhanced ultrasound (CEUS) features before PMWA and within 24 h after PMWA were recorded. Magnetic resonance imaging (MRI) was used for follow-up at 3 and 6 months after PMWA. Transvaginal ultrasound was used for follow-up at 24 months after PMWA.

RESULTS

A total of 50 patients with uterine fibroids received treatment. The median ablation rate of uterine fibroids was 97.21%. The mean lesion volume reduction rates were 32.63%, 57.26%, and 92.64% at 3, 6, and 24 months after treatment, respectively. The size and location of uterine fibroids did not significantly affect the ablation rate and the rate of lesion volume reduction. No major complication was found during and after the procedure.

CONCLUSION

Transabdominal ultrasound- and laparoscopy-guided PMWA can be utilized to safely enhance the ablation rate while minimizing ablation time and avoiding harm to adjacent organs and the endometrium. This technique is applicable for treating uterine fibroids of different sizes and at varying locations.

TRIAL REGISTRATION NUMBER

ChiCTR-IPR-17011910, and date of trial registration: 08/07/2017.

An Evaluation of Ultrasound-Guided Percutaneous Microwave Ablation for the Treatment of Symptomatic Uterine Fibroids

PURPOSE

To evaluate the feasibility and effectiveness of ultrasound-guided percutaneous microwave ablation (MWA) for the treatment of symptomatic uterine fibroids.

MATERIALS AND METHODS

A single-center retrospective study was conducted on 17 patients, mean age 37.5 years (SD ± 7.3; range 19-47 years) with symptomatic uterine fibroid who underwent MWA between September 2018 and December 2022. Outcomes included volume reduction of uterine fibroids, hemoglobin levels, uterine fibroid symptoms, and health-related quality-of-life questionnaire scores before and 12 months after ablation.

RESULTS

Preoperative fibroid diameter was a mean of 6.7 cm (SD ± 1.1; range 5-9 cm), and volume was a mean of 101.9 cm3 (SD ± 63.3; range 16.9-264.1 cm3). The mean ablation time was 12.2 minutes (SD ± 3.1; range, 8-20 minutes). The mean reduction of volume at 12 months after treatment was 70.9% (SD ± 23.8). The hemoglobin level increased significantly from 9.96 g/dL ± 2.33 before treatment to 12.14 g/dL ± 1.34 at 12 months after treatment (P = .002). The symptom severity score and health-related quality-of-life scores were significantly improved at follow-up (P < .001).

CONCLUSIONS

The application of MWA as a standalone treatment method might provide an effective, minimally invasive option for Federation of Gynecology and Obstetrics Types 1-6 symptomatic uterine fibroids with the potential to enhance patients' quality of life.

Role of ultrasound-guided technique in the treatment of gynecologic diseases: A systematic review and meta-analysis

BACKGROUND

The efficacy and safety of ultrasound-guided interventional procedures for gynecologic diseases have not been evaluated comprehensively. Therefore, we aimed to provide an evidence-based medical reference for clinical treatment in this meta-analysis.

METHODS

The literature searches were conducted in databases of PubMed, Embase, and Web of Science for eligible studies published from 2002 to May 2022. All literature was searched, screened, and reviewed by 2 researchers separately. RevMan 5.3.0 was used to analyze the relevant data.

RESULTS

A total of 12 articles consisting of 2854 patients were included. Compared with the control group, meta-analysis showed that ultrasound-guided technique in the experimental group was associated with a higher effective rate [risk ratio = 0.84, 95% confidence interval (CI) (0.84, 0.84)], a lower probability of recurrence [odds ratio = 0.13, 95% CI (0.13, 0.13), P < .00001], and a greater effective reintervention rate [odds ratio = 3.39, 95% CI (1.29, 8.86), P = .01]. However, it was not significantly associated with fewer adverse reactions.

CONCLUSIONS

Ultrasound-guided technique in treating gynecologic diseases exerted a positive effect and had fewer adverse reactions, which could be popularized and applied in clinical practice.

Long term follow-up of uterine fibroids treated with microwave ablation: an up to 3-year observational study of volume, regrowth, and symptoms

OBJECTIVE

To study long-term effects in patients treated with microwave ablation (MWA) for symptomatic uterine fibroids and investigate fibroid characteristics predictive of successful treatment.

METHOD

Women who received MWA treatment for uterine fibroids in a previous study were included. A total of 16 patients underwent contrast enhanced MRI before treatment, postoperatively at 6 months and at long-term follow-up, to assess volumes of treated fibroids (n = 42). Long-term MRI was performed between 16 and 36 months after treatment [median 22 months, interquartile range (IQR) 18.5-27]. Validated questionnaires for evaluation of uterine fibroid symptoms and menstrual bleeding (UFS-QoL and PBAC) were used to assess long-term effects on symptoms. The degree of shrinkage was correlated to vascularization and T2 signal intensity (SI) at preoperative MRI and location of fibroids according to the FIGO classification, using the Mann-Whitney U test.

RESULTS

Most patients (82%) reported improvement up to 3 years after treatment. Out of 42 treated fibroids, 35 (83%) continued to shrink over time with median relative volume reduction of 77% (IQR 39-95). For eight fibroids (19%) which showed low vascularization on the pretreatment MRI, there was less shrinkage compared to well-vascularized fibroids (p = 0.01). Most fibroids (79%) showed iso- to hyperintense T2 signal on preoperative MRI and showed a higher grade of shrinkage than hypointense fibroids (p = 0.02).

CONCLUSION

After microwave treatment improvement is maintained for most patients up to 36 months and most fibroids showed continuous shrinkage. Preoperative vascularization, high T2 SI and submucosal location predicted continuous volume reduction. However, to confirm this, larger studies are needed.

Ultrasound-guided percutaneous microwave ablation for uterine fibroids: mid-term local treatment efficiency and associated influencing factors

OBJECTIVE

To investigate the mid-term local treatment efficiency of ultrasound-guided percutaneous microwave ablation (MWA) for uterine fibroids (UFs) and the associated influencing factors.

METHODS

From July 2020 to October 2021, a total of 28 patients with 52 UFs who had undergone ultrasound-guided MWA were retrospectively included in this study. Pre-treatment clinical characteristics, conventional ultrasound and contrast-enhanced ultrasound (CEUS) features were analyzed to explore their correlation with volume reduction ratios (VRRs) of sufficient ablation (i.e. a VRR of at least 50% at the 3 month follow-up). The patients were assessed at 1-, 3-, 6 month follow-up after MWA treatment and the assessment included VRR, adverse events, uterine fibroid symptom (UFS) and quality of life (QoL) scores, and clinical symptoms.

RESULTS

The procedures of percutaneous MWA for UFs were tolerated well and no major complications occurred in all patients. At the 1-, 3-, 6 month follow-up, the median VRRs of UFs were 30.1%, 46.9%, and 65.8%, respectively. At the 3 month follow-up, 44.4% of fibroids obtained sufficient ablation while the remaining 55.6% obtained partial ablation (i.e. a VRR of <50%). Non-enhancing area during the early phase (i.e. within 30 s after injecting contrast agent) on pre-treatment CEUS was present in 22.2% UFs, which was associated with sufficient ablation at the 3 month follow-up (p < 0.05). In addition, the relevant clinical symptoms of all patients were alleviated or removed. The UFS and QoL score after MWA decreased significantly in comparison with those after MWA (p = 0.04 and p = 0.057, respectively), indicating a remarkable improvement of clinical symptom and QoL.

CONCLUSION

Ultrasound-guided MWA is an effective and safe method to treat patients with UFs. Non-enhancing area during the early phase on pretreatment CEUS is associated with mid-term local treatment efficiency, which might be used to predict treatment outcome.

ADVANCES IN KNOWLEDGE

Non-enhancing area during the early phase on pretreatment CEUS is an important factor associated with mid-term local treatment efficiency. This is the first study finding that CEUS feature can be used as a marker for the prediction of mid-term local treatment response.

Ultrasound guided microwave ablation compared to uterine artery embolization treatment for uterine fibroids - a randomized controlled trial

OBJECTIVE

To evaluate the efficacy, feasibility and acceptability of microwave ablation (MWA) compared to uterine artery embolization (UAE) as treatment for uterine fibroids.

METHOD

A randomized controlled superiority trial, including premenopausal women 30-55 years, with symptomatic uterine fibroids without any single fibroid exceeding mean diameter of eight centimeters. Patients were randomized to receive microwave ablation, performed abdominally or vaginally, or to uterine artery embolization. The primary outcome was volume difference of the three largest fibroids at 6 months post treatment evaluated by magnetic resonance imaging (MRI) by a blinded radiologist analyzed by Mann-Whitney U-test. Secondary outcomes included symptom severity score (SSS), health related quality of life (HR-QoL), amount of menstrual bleeding, postoperative pain, length of hospitalization, need for additional treatment, adverse events and if patients would recommend the treatment to a friend.

RESULTS

Patients were recruited from 30 January 2017 to 12 September 2019, with a total of 17 patients treated in each group from May 2017 to December 2019. Superiority of MWA could not be established. The volume reduction was 41.8% (Interquartile range, IQR, 14-63) in the MWA group compared to 62.2% (IQR 34.9-80.1) in the UAE group (p = 0.29). Effects on symptoms, HR-QoL and acceptability did not differ between groups. Days of hospitalization and sick leave were significantly fewer in the MWA group (p < 0.001 and p = 0.001).

CONCLUSIONS

Although superiority of MWA could not be established, it is a promising technique for treating uterine fibroids. It was well tolerated and associated with lower use of health care resources. Trial registration: NCT02942537, www.clincialtrials.gov.

Comparison of thermal ablative methods and myomectomy for the treatment of fibroids: a systematic review and meta-analysis

OBJECTIVE

To examine the effectiveness and safety of thermal ablative methods and myomectomy for the treatment of uterine fibroids.

MATERIALS AND METHODS

We searched EMBASE, PubMed, the Cochrane Central Register of Controlled Trials, Scopus, CINAHL, ClinicalTrials.gov and Web of Science databases through April 2021. Clinical trials comparing the thermal ablative methods and myomectomy for the treatment of uterine fibroids were included.

RESULTS

Thirteen studies including 4205 patients were eligible. The thermal ablative treatment group was associated with less major adverse events (only ultrasound guided high-intensity focused ultrasound) (RR, 0.111 [95% CI, 0.070-0.175], p=.0), shorter duration of hospital stays in observational studies (-0.1497 day, [95% CI, -1.593 to -0.321], p=.0) and in randomized controlled trials (RCTs) (-0.844 day, [95% CI, -0.1.142 to -0.546], p=.0), higher uterine fibroid symptom (UFS) score after operation (0.252 [95% CI, 0.165-0.339]; p=.0), transformed symptom severity (tSS) score after operation (0.515 [95% CI, 0.355-0.674]; p=.0) and quality of life (QoL) score after operation (0.188 [95% CI, 0.093-0.283]; p=.0) in comparison with myomectomy group. No statistically significant difference was found between the thermal ablative treatment group and myomectomy group with respect to reintervention rate and pregnancy rate.

CONCLUSION

The current data available demonstrate that thermal ablative methods were not inferior to myomectomy in the treatment of uterine fibroids. The findings in this study need to be further confirmed by large RCTs.

Temperature-dependent dielectric properties of human uterine fibroids over microwave frequencies

Microwave ablation is under investigation as a minimally-invasive treatment for uterine fibroids. Computational models play a vital role in the development, evaluation and characterization of candidate ablation devices. The temperature-dependent dielectric properties of fibroid tissue are essential for accurate computational modeling.Objective:To measure the broadband temperature-dependent dielectric properties of uterine fibroids excised during hysterectomy procedures.Methods: The open-ended coaxial probe method was employed for measuring the broadband dielectric properties of freshly excised human uterine fibroid samples (n = 6) obtained from an IRB-approved tissue bank. The dielectric properties (relative permittivity,ε_r, and effective electrical conductivity,σ_eff) were evaluated at temperatures ranging from 23 °C-150 °C, over the frequency range of 0.5-6 GHz. Linear piecewise parametrization with respect to temperature and quadratic parametrization with respect to frequency was applied to characterize broadband temperature-dependent dielectric properties of fibroid tissue.Results: The baseline room temperature values ofε_rvary from 57.5 ± 5.29 to 44.5 ± 5.77 units andσ_effchanges from 0.91 ± 0.19 to 6.02 ± 0.7 S m^-1over the frequency range of 0.5-6 GHz. At temperatures close to the water vaporization point,ε_r, drops considerably i.e. to 12%-14% of its baseline value for all measured frequencies.σ_effvalues initially rise till 98 °C and then fall to 11%-13% of their baseline values at 125 °C for frequencies ≤2.45 GHz. Theσ_efffollows a decreasing trend for frequencies >2.45 GHz and drops to ∼6 % of their baseline room temperature values.Conclusion:The temperature dependent dielectric properties of uterine fibroid tissues over microwave frequency range are reported for the first time in this study. Parametric models of uterine fibroid dielectric properties are also presented for incorporation within computational models of microwave ablation of fibroids.

Ultrasound-guided Microwave Ablation in the Management of Symptomatic Uterine Myomas: A Systematic Review and Meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the clinical effects and safety of ultrasound-guided microwave ablation (MWA) for the treatment of symptomatic uterine myomas.

DATA SOURCES

We searched PubMed, Web of Science Core Collection, Cochrane Library, Embase, Scopus, and Google Scholar for studies from January 2000 to January 2021.

METHODS OF STUDY SELECTION

We included all studies that reported the clinical outcomes of ultrasound-guided MWA in women with symptomatic uterine myomas. Two researchers conducted the study selection according to the screening criteria.

TABULATION, INTEGRATION, AND RESULTS

We evaluated the risk of bias and evidence quality using the Newcastle-Ottawa scale. Two researchers independently extracted information from the included studies. We extracted the standardized mean difference (SMD) and pooled proportion with a 95% confidence interval (CI) for the outcome measures of interest. A total of 10 studies representing 671 patients were included. The Uterine Fibroid Symptom and Quality of Life (UFS-QoL) questionnaire was used to assess the clinical effects. Compared with baseline, the UFS scores decreased significantly (SMD 3.37; 95% CI, 2.27-4.47; p <.001; reduction rate 65.9%), QoL scores increased significantly (SMD -3.12; 95% CI, -3.93 to -2.30; p <.001; rate of increase 72.0%), and hemoglobin concentration increased significantly (SMD -2.13; 95% CI, -3.44 to -0.81; p = .002; rate of increase 30.3%) at follow-up. The mean operation time was 34.48 minutes (95% CI, 22.82-46.13; p <.001). The rate of reduction in myoma volume after MWA was 85.3% (95% CI, 82.7%-88.0%, p <.001). No major adverse event was reported, and the incidence of minor adverse events was 21.1% (95% CI, 15.1%-27.0%, p <.001).

CONCLUSION

Ultrasound-guided MWA is an effective and safe minimally invasive therapy for symptomatic uterine myomas.

Transcervical microwave ablation in type 2 uterine fibroids via a hysteroscopic approach: analysis of ablation profiles

Type 2 uterine fibroids are challenging to resect surgically as ≥ 50% volume of myoma lies within the myometrium. A hysteroscopic approach for ablating fibroids is minimally-invasive, but places a considerable burden on the operator to accurately place the ablation applicator within the target. We investigated the sensitivity of transcervical microwave ablation outcome with respect to position of the ablation applicator within 1 - 3 cm type 2 fibroids.Methods:A finite element computer model was developed to simulate 5.8 GHz microwave ablation of fibroids and validated with experiments inex vivotissue. The ablation outcome was evaluated with respect to applicator insertion angles (30°, 45°, 60°) , depth and offset from the fibroid center (±2 mm for 3 cm fibroid and ±1 mm for 1 cm fibroid) with 35 W and 15 W applied power for 3 cm and 1 cm fibroids, respectively. Power deposition was stopped when thermal dose of 40 cumulative equivalent minutes at 43 °C (CEM43) was accrued in adjacent myometrium.Results:Within the range of all evaluated insertion angles, depths and offsets, the ablation coverage was less sensitive to variation in angle as compared to depth and offset, and ranged from 34.9 - 83.6% for 3 cm fibroid in 140 - 400 s and 34.1 - 67.9% for 1 cm fibroid in 30 - 50 s of heating duration. Maximum achievable ablation coverage in both fibroid cases reach ∼ 90% if thermal dose is allowed to exceed 40 CEM43 in myometrium.Conclusion:The study demonstrates the technical feasibility of transcervical microwave ablation for fibroid treatment and the relationship between applicator position within the fibroid and fraction of fibroid that can be ablated while limiting thermal dose in adjacent myometrium.

Assessment of thermal damage to myometrium during microwave ablation of uterine fibroids

Thermal ablation techniques are increasingly used for the treatment of symptomatic uterine fibroids. Thermal protection of myometrial tissue adjacent to the fibroid from ablation is critical to maximally preserve the uterus. This study presents a bench top experimental setup, using ex vivo bovine muscle as a surrogate tissue, for evaluating collateral thermal damage in tissues during fibroid ablation. The study reports on the effect of applicator insertion angles (67.5° and 90°) into a mock fibroid on the efficacy of treatment. 6 experiments were performed (3 for each insertion angle) with 30 W applied power at 2.45 GHz. The heating duration was restricted to the time at which a thermal dose of 10 cumulative equivalent minutes at 43 °C (10 CEM 43) was accrued at the boundary of the mock fibroid. Results showed that the volume of ablation inside the mock fibroid dropped considerably from 66% to 17% when the applicator insertion angle was changed from 90º to 67.5º, suggesting that insertion angle plays an important role during microwave ablation of fibroid. The proposed setup provides a method for validating computational models for accurate and safe delivery of ablation to target tissues in fibroid treatment.

Uterine Myomas: Extravascular Treatment

Uterine fibroids are common benign tumors that affect the female reproductive tract. They are responsible for considerable morbidity and deterioration of life quality. The main advantages offered by mini invasive techniques are low grade of invasiveness and short times of hospitalization. The most diffuse technique is uterine artery embolization (UAE). Common concerns with UAE include postprocedural pain, postembolization syndrome, and risk of infection. Image-guided thermal ablation techniques like radiofrequency ablation, percutaneous microwave ablation, and imaging-guided high-intensity focused ultrasound were introduced to overcome the side effects related to UAE and surgery. The aim of this review is to briefly analyze the ablative procedures and their role in the management of symptomatic fibroids, and to describe the safety profile and outcomes of these modalities.

Successful management of diaphragmatic ectopic pregnancy using ultrasound-guided percutaneous microwave ablation

Diaphragmatic ectopic pregnancy is a rare status during the perinatal period. We reported that a 24-year-old woman with diaphragmatic ectopic pregnancy successfully received ultrasound-guided percutaneous microwave ablation. It found that beta-human chorionic gonadotropin level decreased showing 1067, 311.3 and 118.4 mIU/mL within five postoperative days, and P level reduced from 3.64 to 1.59 nmol/L. Contrast-enhanced ultrasonography image on the third day after ablation indicated that there was no enhancement in the lesion. This case indicated that ultrasound-guided percutaneous microwave ablation could be critical for a good outcome in diaphragmatic ectopic pregnancy.

Submyometrial vasopressin injection before microwave ablation of vascular-rich submucosal myomas: a preliminary case study

Purpose: Vascular-rich myomas are resistant to treatment involving transcervical microwave myolysis. To overcome cooling by blood perfusion, we injected dilute vasopressin solution into the space between the myometrium and the surface of the vascular-rich myomas. Material and Methods: Seven outpatients [age (mean ± SD age), 44.9 ± 3.9 years] with a single symptomatic vascular-rich submucosal myoma measuring 4.2-9.2 cm (6.5 ± 2.5 cm) underwent transcervical microwave myolysis and microwave endometrial ablation. Before microwave irradiation, dilute vasopressin solution was injected into the space between the myometrium and the surface of the vascular-rich myoma. We assessed the changes in the volumes of the vascular-rich myomas and blood hemoglobin levels before and 3 and 6 months after treatment. In addition, improvements in menorrhagia and satisfaction after the operation were assessed using visual analog scales. Results: Submyometrial injection of dilute vasopressin effectively reduced the abundant blood flow. The vascular-rich myomas were necrotized and shrank significantly by 69.0% at 3 months and 72.4% at 6 months after the operation (p < .05). Blood hemoglobin levels significantly increased at 3 months (p < .01). In addition, the visual analog scale results indicated that menorrhagia improved subjectively and the patients were satisfied with the results of the operation. Conclusions: Vasopressin injection before transcervical microwave myolysis leads to extended necrosis of vascular-rich submucosal myomas.

Percutaneous High Frequency Microwave Ablation of Uterine Fibroids: Systematic Review

Uterine fibroids are the most common benign pelvic tumor of the female genital tract and tend to increase with age; they cause menorrhagia, dysmenorrhea, pelvic pressure symptoms, back pain, and subfertility. Currently, the management is based mainly on medical or surgical approaches. The nonsurgical and minimally invasive therapies are emerging approaches that to the state of the art include uterine artery embolization (UAE), image-guided thermal ablation techniques like magnetic resonance-guided focused ultrasound surgery (MRgFUS) or radiofrequency ablation (RF), and percutaneous microwave ablation (PMWA). The purpose of the present review is to describe feasibility results and safety of PMWA according to largest studies available in current literature. Moreover technical aspects of the procedure were analyzed providing important data on large scale about potential efficacy of PMWA in clinical setting. However larger studies with international registries and randomized, prospective trials are still needed to better demonstrate the expanding benefits of PMWA in the management of uterine fibroids.

Successes and failures of uterine leiomyoma drug discovery

INTRODUCTION

To-date, the only cure for symptomatic uterine fibroids (UFs) is surgical intervention. However, surgery may eliminate the hope of future pregnancies; moreover, the intrinsic risks of surgery make it a less favorable to women with UFs. Because of this, conservative medical therapies have become an attractive and prior option for those women. Leuprolide acetate (LA), a gonadotropin-releasing hormone (GnRH) agonist, is the only pharmacological agent currently approved for the short-term and pre-operative management of symptomatic UFs in the USA. Areas covered: This systematic review covers the successes and failures of prominent drugs that have been researched for UFs in the past and agents that have shown promise in recent clinical trials. The most recent clinical trials and advances in drug therapy are presented in a comprehensive overview outlining the direction UF drug discovery is heading. Expert opinion: Experts in the field are already on the forefront leading the responsibility to uncover potential drugs as long term fertility friendly viable options for non-invasive treatment/prevention of UFs. Indeed, a shift in the UF management is expected in the future.

Contrast-enhanced ultrasound is better than magnetic resonance imaging in evaluating the short-term results of microwave ablation treatment of uterine fibroids

Contrast-enhanced ultrasound (CEUS) and magnetic resonance imaging (MRI) were compared in evaluating the short-term effects of microwave ablation (MWA) on uterine fibroids. A total of 60 patients with uterine fibroids treated by MWA were enrolled in the experimental group during their two-year follow-up period according to the inclusion criteria. Conventional two-dimensional US, MRI and CEUS were performed to determine the volume reduction and the fibroid residue by displaying the size, echo and signal intensity of fibroids prior to and after MWA treatment. As the control group, 60 consecutive patients were recruited on their follow-up visit at least two years after MWA treatment of uterine fibroids. Significant differences were observed in the wash-in rate (WiR) of the fibroid tissue, start time difference, rise time ratio (RTR) and WiR ratio between the experimental and control groups (P<0.05). However, the WiR of fibroid vessel, total area under the curve of fibroid vessel and tissue, and rise time difference (RTD) between fibroid vessel and tissue did not display any significant differences between the two groups. Fibroids were either reduced in volume or cured by MWA therapy in patients with uterine fibroids. The reductions in volume of hypointense, isointense and hyperintense fibroids were 62.42±18.13, 53.27±10.05 and 47.43±9.56%, respectively, on T1-weighted imaging (T1WI). On T2WI, the corresponding reductions were 67.32±32.63, 59.36±19.36 and 42.63±10.37%, respectively. The higher the signal intensity on T1WI and T2WI, the lower the reduction in volume. It is indicative that different blood supply to fibroids results in different ablation. CEUS was proved to be more effective than MRI in evaluating the effects of MWA on uterine fibroids during the first postoperative year.

Status and advancement of microwave ablation in China

Tumour ablation is defined as the direct application of chemical or thermal therapy to eradicate or substantially destroy a tumour. Currently, minimally invasive ablation techniques are available for the local destruction of focal tumours in multiple organ sites. Microwave ablation (MWA) is premised on the biological response of solid tumours to tissue hyperthermia, and it is a relatively low-risk procedure. Due to several advantages of MWA, including higher thermal efficiency, higher capability for coagulating blood vessels, faster ablation time and the simultaneous application of multiple antennae, MWA could be a promising minimally invasive ablation technique for the treatment of solid tumours. Therefore, the use of MWA has developed rapidly in China during the last decade. Many successful studies have been performed, and widespread use has been achieved for multiple types of tumours in China, especially for liver cancer. This review will describe the state-of-the-art of MWA in China, including the development of MWA equipment and its application in the treatment of multiple types of tumours.

Effectiveness of ultrasound-guided percutaneous microwave ablation for symptomatic uterine fibroids: a multicentre study in China

PURPOSE

To evaluate the clinical efficacy of ultrasound-guided percutaneous microwave ablation (PMWA) therapy for symptomatic uterine fibroids in a multicentre study.

MATERIALS AND METHODS

Patients with symptomatic uterine fibroids who underwent PMWA at multiple treatment centres in China between January 2013 and August 2015 were prospectively studied to compare the reduction rate of uterine fibroids, haemoglobin level and uterine fibroid symptom and health-related quality of life questionnaire (UFS-QOL) scores before and at 3, 6 and 12 months after ablation.

RESULTS

A total of 311 patients (405 leiomyomas) from eight treatment centres underwent the treatment (age, 29-55 years; mean ± SD, 41 ± 5.11 years). The mean diameter of the myomas ranged from 2.03 to 12.50 cm (mean, 5.10 ± 1.28 cm) and the volume ranged from 4.40 to 1022.14 cm³ (mean, 95.01 ± 70.29 cm³). Forty-eight myomas were identified as FIGO type 1/2 fibroids, 256 as type 3/4 fibroids and 101 as type 5/6 fibroids. The mean ablation rate was 86.6% (54.0-100%). The mean reduction rate was 63.5%, 78.5% and 86.7% at 3, 6 and 12 months posttreatment, respectively. The haemoglobin level increased significantly from 88.84 ± 9.31 g/L before treatment to 107.14 ± 13.32, 116.05 ± 7.66 and 117.79 ± 6.51 g/L at 3, 6 and 12 months posttreatment, respectively (p = .000). The symptom severity score (SSS) and health-related quality of life (HRQL) scores were also significantly improved posttreatment compared with before treatment (p = .000).

CONCLUSION

PMWA is an effective, minimally invasive treatment for symptomatic leiomyomas that can significantly improve the quality of life of patients.

Laparoscopic Radiofrequency Thermal Ablation for Uterine Adenomyosis

BACKGROUND AND OBJECTIVES

Symptomatic uterine adenomyosis, unresponsive to medical therapy, is a challenging condition for patients who desire to preserve their uterus. This study was an evaluation of the feasibility and efficacy of laparoscopic radiofrequency thermal ablation of symptomatic nodular uterine adenomyosis.

METHODS

Fifteen women with symptomatic nodular adenomyosis, who had no plans for pregnancy but declined hysterectomy, underwent radiofrequency thermal ablation. Ultrasonography was performed at baseline and at postoperative follow-ups at 3, 6, 9, and 12 months. The impact of uterine adenomyosis-related symptoms was assessed according to the visual analog scale.

RESULTS

The median number of nodular lesions treated per patient was 1 (range, 1-2). The median baseline volume of the adenomyosis area was 60 cm(3) (range, 18-128). The median reduction in volume was 32, 49.4, 59.6, and 65.4% at 3, 6, 9, and 12 months, respectively. A significant progressive improvement in the symptoms score was observed at the 4 follow-ups.

CONCLUSION

In this study, laparoscopic radiofrequency thermal ablation reduced uterine adenomyosis-related symptoms and volume, with significant relief of symptoms.

Evaluation of MRI protocols for the assessment of lumbar facet joints after MR-guided focused ultrasound treatment

BACKGROUND

MR-guided focused ultrasound (MRgFUS) might be a very safe and effective minimally invasive technique to treat facet joint pain caused by arthritis and other degenerative changes. However, there are still safety concerns for this treatment and challenges regarding MR imaging and temperature mapping due to susceptibility effects between the bone and soft tissue near the joint, which has resulted in poor MR image quality. The goal of this research was to evaluate multiple magnetic resonance imaging (MRI) pulse sequences for characterizing ablated lumbar facet joint lesions created by high-intensity focused ultrasound (FUS) and compare the findings to histological tissue assessment. In particular, we investigated the use of T2-weighted MRI to assess treatment effects without contrast administration.

METHODS

An IACUC approved study (n = 6 pigs) was performed using a 3T widebore MRI system equipped with an MRgFUS system. Facet joints of the lumbar vertebra were ablated using 1-MHz frequency and multiple sonication energies (300-800 J). In addition to T2-weighted MRI for treatment planning, T1-, T2-, and T2*-weighted and perfusion MRI sequences were applied. Signal intensity ratios of the lesions were determined. Histopathology was used to characterize cellular changes.

RESULTS

Ablation of the facet joint, using MRgFUS, was successful in all animals. T2-weighted images showed high signal intensity in the edematous facet joint and adjacent muscle, while delayed contrast-enhanced T1-weighted images showed an enhanced ring surrounding the target volume. T2*-weighted GRE images revealed inconsistent lesion visualization. Histopathology confirmed the presence of cellular coagulation (shrinkage), extracellular expansion (edema), and hemorrhage in the bone marrow.

CONCLUSIONS

MRgFUS provided sufficient precision and image quality for visualization and characterization of ablated facet joints directly after ablation. MRI may help in monitoring the efficacy of FUS ablation without contrast after treating patients with back pain.

Unplanned pregnancy after ultrasound-guided percutaneous microwave ablation of uterine fibroids: A follow-up study

A follow-up study was performed with 169 women of childbearing age who underwent ultrasound-guided percutaneous microwave ablation (UPMWA) therapy for symptomatic uterine fibroids in the Chinese PLA General Hospital from June 2007 to December 2014. This study aimed to observe the incidence of unplanned pregnancies in these women after UPMWA treatment in order to evaluate its effect on natural conception. Ten unplanned pregnancies in nine women were occurred. Of the nine patients, six did not want the pregnancy and chose for induced abortion to end the pregnancy at an early stage. Three chose to continue with the pregnancy and gave birth to a healthy term infant delivered by cesarean section (of these three patients, two had been previously diagnosed as infertility). None of the patients had any serious obstetric complications. After UPMWA treatment for uterine fibroids, patients may conceive naturally, the impact of the procedure on fertility and pregnancy outcomes is worthy of further prospective study in larger sample.

Ultrasound-guided percutaneous microwave ablation for adenomyosis: efficacy of treatment and effect on ovarian function

A total of 142 premenopausal women with symptomatic adenomyosis underwent ultrasound (US)-guided percutaneous microwave ablation (PMWA) at the Chinese PLA General Hospital. This study aimed to evaluate changes in serum pituitary, gonadal hormone and cancer antigen 125 (CA125) levels after US-guided PMWA. Therefore, estradiol (E₂), follicle-stimulating hormone (FSH), prolactin (PRL) and CA125 levels were evaluated before ablation and at 3, 6, 9 and 12 months after ablation. No significant differences were observed in the E₂ and FSH levels pre-ablation and during follow-up (E₂: p = 0.933, p = 0.987, p = 0.106, p = 0.936; FSH: p = 0.552, p = 0.295, p = 0.414, p = 0.760). The mean absolute values of serum CA125 and PRL were significantly decreased at 3, 6, 9 and 12 months after ablation (CA125: p < 0.001, p < 0.001, p < 0.001, p = 0.003; PRL: p < 0.001, p < 0.001, p < 0.001, p < 0.001). A significant correlation between changes in CA125 levels and uterine volume was found (p < 0.001). No evidence of a decline in ovarian function was observed after US-guided PMWA.

Thermal ablative treatment of uterine fibroids

In addition to surgical methods of treating uterine fibroids, numerous non-invasive treatments have been developed. Many of these involve the use of hyperthermia, the heating of tissue by a variety of methods. These include the use of lasers, radiofrequency, microwave energy and high intensity focused ultrasound, guided by both ultrasound and magnetic resonance imaging. In this review we examine the technology behind these treatment modalities and review the current evidence for their use.

A retrospective comparison of microwave ablation and high intensity focused ultrasound for treating symptomatic uterine fibroids

OBJECTIVES

To retrospectively compare the effectiveness and safety of percutaneous microwave ablation (PMWA) and ultrasound-guided high-intensity focused ultrasound (USgHIFU) for treating symptomatic uterine fibroids.

METHODS

Seventy-three women with symptomatic uterine fibroids who met the inclusion criteria were enrolled in our study from September 2012 to December 2013. Thirty-one patients with forty uterine fibroids underwent PMWA, and forty-two patients with fifty-one uterine fibroids underwent USgHIFU. A contrast-enhanced MRI was performed before and after treatment, and all patients were followed up for 6 months. Assessment endpoints included symptom severity scores (SSS), treatment time, ablation rate, fibroid regression rate and adverse events.

RESULTS

The mean age of the patients in our study was 35.4±6.2 years (range, 21-49 years), and the median volume of uterine fibroids was 95.7cm(3) (60.3-131.5cm(3)). The ablation rate of uterine fibroids was 79.8±18.2% and 77.1±14.9% in the PMWA group and the USgHIFU group, respectively, and showed no significant difference between the groups. Changes in SSS after PMWA were similar in the PMWA group (47.7 pre-treatment vs. 29.9 post-treatment) and USgHIFU group (42.1 pre-treatment vs. 24.6 post-treatment). The regression rate of uterine fibroids also showed no marked difference between the two groups (PMWA, 50.3%; USgHIFU, 52.4%). The median treatment time of the PMWA group was 46.2min, which was demonstrably superior to USgHIFU. Finally, the occurrence rate of adverse events was the same in the two groups.

CONCLUSIONS

The safety and effectiveness of PMWA and USgHIFU in the treatment of uterine fibroids were similar; however, the median treatment time of PMWA was shorter than that of USgHIFU.

Research of dose-effect relationship parameters of percutaneous microwave ablation for uterine leiomyomas--a quantitative study

Eighty eight patients with 91 uterine leiomyomas who underwent ultrasound-guided percutaneous microwave ablation (PMWA) treatment were prospectively included in the study in order to study the dose-effect relationship parameters (DERP) of PMWA for uterine leiomyomas and its relationship with T2-weighted MR imaging (T2WI). Based on the signal intensity of T2WI, uterine leiomyomas were classified as hypointense, isointense, and hyperintense. During ablation, leiomyomas were treated with quantitative microwave ablation (QMWA) energy of 50 w × 300 s or 60 w × 300 s. After QMWA, contrast-enhanced ultrasound (CEUS) was performed to evaluate DERP. No matter under 50 w × 300 s or 60 w × 300 s, quantitative microwave ablation volume (QMAV) of hyperintense leiomyoma was smaller than that of hypointense and isointense leiomyoma (P<0.016). For hypointense and isointense leiomyoma, QMAV of 60 w × 300 s was larger than that of 50 w × 300 s (P<0.05). DERPs obtained by T2WI can be used to guide the treatment of uterine leiomyoma by PMWA.

Feasibility study on energy prediction of microwave ablation upon uterine adenomyosis and leiomyomas by MRI

OBJECTIVE

To evaluate the feasibility of energy prediction of percutaneous microwave ablation (PMWA) upon uterine leiomyomas and adenomyosis by MRI.

METHODS

63 patients (49 patients with 49 uterine leiomyomas and 14 patients with adenomyosis) who underwent ultrasound-guided PMWA treatment were studied during the period from June 2011 to December 2012. Before PMWA, contrast-enhanced MRI (ceMRI) was performed for all of the patients. Based on the signal intensity (SI) of T2 weighted MRI, uterine leiomyomas were classified as hypointense, isointense and hyperintense. During ablation, the output energy of the microwave was set at 50 W, and T11a microwave antennas were used. ceMRI was performed within 7 days after PMWA treatment. Non-perfused volume and energy required per unit volume were analysed statistically.

RESULTS

When unit volume of lesions was ablated, uterine adenomyosis needed more energy than did uterine leiomyomas, and hyperintense uterine leiomyomas needed more energy than did hypointense pattern.

CONCLUSIONS

MRI SI of uterine leiomyomas and uterine adenomyosis can be used to predict PMWA energy.

ADVANCES IN KNOWLEDGE

The conclusions indicate that MRI SI can be used to perform pre-treatment planning, which will make the treatment more precise.