Effects of a microbubble ultrasound contrast agent on high-intensity focused ultrasound for uterine fibroids: a randomised controlled trial

Ultrasound Molecular Imaging Enhances High-Intensity Focused Ultrasound Ablation on Liver Cancer With B7-H3-Targeted Microbubbles

BACKGROUND

High-intensity focused ultrasound (HIFU) is a promising minimally invasive treatment for liver cancer; however, its efficacy is often limited by the attenuation of ultrasonic energy. This study investigates the effectiveness of B7-H3-targeted microbubbles (T-MBs) in enhancing HIFU ablation of liver cancer and explores their potential for clinical translation.

METHODS

T-MBs and isotype control microbubbles (I-MBs) were synthesized through the conjugation of biotinylated anti-B7-H3 antibody and isotype control antibody to the microbubble surface, respectively. Contrast-enhanced ultrasound imaging was performed to compare the accumulation of T-MBs and I-MBs in liver cancer at various time points. The efficacy of T-MBs in enhancing HIFU treatment was evaluated by measuring the immediate tumor ablation rate and long-term tumor growth suppression. Additionally, the induced antitumor immune response was assessed through cytokine quantification in serum and tumor tissue, along with immunofluorescence staining conducted on days 1, 3, and 7 post-treatment.

RESULTS

T-MBs demonstrated superior liver cancer-specific accumulation, characterized by higher concentrations and prolonged retention compared to I-MBs. The combination of T-MBs with HIFU resulted in significantly enhanced tumor ablation rates and superior tumor growth suppression. Post-treatment analysis revealed a gradual uptick in cytokine levels within the tumor microenvironment, along with progressive infiltration of antitumor immune cells.

CONCLUSION

T-MBs effectively enhance the therapeutic efficacy of HIFU for liver cancer treatment while simultaneously promoting an antitumor immune response. These findings provide a strong experimental foundation for the clinical translation of ultrasound molecular imaging combined with HIFU as a novel approach for tumor therapy.

A systematic review of the side effects of high-intensity focused ultrasound ablation of uterine fibroids

Background

A new intervention called high-intensity focused ultrasound (HIFU) targets fibroids with high-intensity ultrasound pulses using ultrasound probes. This noninvasive method, which can be carried out with either magnetic resonance imaging or ultrasound guidance, results in immediate coagulated necrosis within a clearly defined area a few millimeters in diameter.

Methods

This systematic review evaluated the safety of HIFU in the treatment of uterine fibroids regardless of site or size. We specifically aimed to determine the incidence of side effects that can occur during and after HIFU. We searched the PubMed, Scopus, ScienceDirect, and Mendeley archive using only the terms HIFU and fibroid. After identifying 1077 studies of different types from 2014 to March 2024, 300 studies were screened and 60 included.

Results

According to Society of Interventional Radiology guidelines, class A adverse events (AEs) showed no significant results, and individuals with these AEs required no treatment and had no long-term consequences. Similarly, there were no class B significant results. However, 3943 of 10,204 patients (38%) complained of lower abdominal pain after the procedure, a class B AE, which resolved by analgesics. Further, 153 of 24,700 patients (0.6%) had skin burns, blisters, or nodules, and these issues resolved with conservative treatment. Additionally, 74 of 23,741 patients (0.3%) had hematuria; 882 of 5970 patients (14.7%) had abnormal vaginal discharge; 414 of 23,449 (1.7%) had vaginal bleeding; and 267 of 7598 (3.5%) had leg paresthesia. Major AEs (class C and D) were almost nonexistent, and the incidence of death in our study was zero.

Conclusion

HIFU ablation of uterine fibroids is generally safe, causing mostly mild side effects and very few severe complications. The relative safety of HIFU compared to other minimally invasive techniques, such as uterine artery embolization, still needs further evaluation.

Combination of HIFU with sulfur hexafluoride microbubbles in the treatment of solitary uterine fibroids: a systematic review and meta-analysis

OBJECTIVES

To assess the efficacy and safety of sulfur hexafluoride microbubbles on ultrasound-guided high-intensity focused ultrasound (HIFU) ablation of uterine fibroids.

METHODS

Studies that compared HIFU-microbubble combination with HIFU-only in patients with uterine fibroids were searched from inception to April 2022. The standardized mean difference (SMD) or relative risk (RR) with 95% confidence interval (CI) for different outcome parameters was calculated.

RESULTS

Seven studies were included, with a total of 901 patients (519 in the combination group and 382 in the HIFU-only group). The energy consumption for treating 1 cm3 of the lesion in the combination group was less than that in the HIFU-only group [SMD =  - 2.19, 95%CI (- 3.81, - 0.57), p = 0.008]. The use of microbubbles was associated with shortening the duration of the treatment and sonication [SMD =  - 2.60, 95%CI (- 4.09, - 1.10), p = 0.0007; SMD =  - 2.11, 95%CI (- 3.30, - 0.92), p = 0.0005]. The rates of significant greyscale changes during HIFU were greater in the combination group, as well as the increase of non-perfused volume ratio [RR = 1.26, 95%CI (1.04, 1.54), p = 0.02; SMD = 0.32, 95%CI (0.03, 0.61), p = 0.03]. The average sonication durations to reach significant greyscale changes and for ablating 1 cm3 of the fibroid lesion were shorter in the combination group [SMD =  - 1.24, 95%CI (- 2.02, - 0.45), p = 0.002; SMD =  - 0.22, 95%CI (- 0.42, - 0.02), p = 0.03]. The two groups had similar post-HIFU adverse effects, while the combination group had fewer intraprocedural adverse events like abdominal pain, sacrum pain, and leg pain.

CONCLUSIONS

Sulfur hexafluoride microbubbles can be safely used to enhance and accelerate the ablation effects of HIFU in the treatment of uterine fibroids.

CLINICAL RELEVANCE STATEMENT

The combination of HIFU with sulfur hexafluoride microbubbles offers a promising non-invasive treatment option for patients with uterine fibroids.

KEY POINTS

• Sulfur hexafluoride microbubbles combined with ultrasound-guided high-intensity focused ultrasound (USgHIFU) has potential advantages in the treatment of uterine fibroids. • Sulfur hexafluoride microbubbles not only enhance the effects of USgHIFU treatment for uterine fibroids but also shorten its duration. • Sulfur hexafluoride microbubbles do not increase the incidence of USgHIFU-related adverse events in the treatment of uterine fibroids.

Safety of Sonazoid in Assisting High-Intensity Focused Ultrasound Ablation Therapy for Advanced Liver Malignant Lesions: A Single-Arm Clinical Study

OBJECTIVE

The aim of the study described here was to evaluate the safety of Sonazoid-assisted high-intensity focused ultrasound (HIFU) in the treatment of advanced malignant liver lesions.

METHODS

A single-arm study was designed to enroll participants who were diagnosed with advanced primary liver cancer or liver metastases and proposed to receive Sonazoid assistance during HIFU treatment. Serological examination was conducted within 1 wk, and side effects in each patient were monitored for 1 mo. To evaluate therapeutic efficacy, the contrast-enhanced magnetic resonance imaging was performed 1 mo after treatment, and short-term follow-up was conducted a year later.

RESULTS

A total of 17 participants (12 male, 5 female) with an average age of 58 y (range: 46-73 y) were enrolled, including 11 patients with hepatocellular carcinoma, 2 patients with hepatic metastasis and 4 patients with cholangiocarcinoma. The total volume of tumor mass was 111.82 (11.01-272.30) cm3. The average total ablation time for a patient was 2021 ± 1030 s, and the energy efficiency factor was 5979.7 (3108.0, 45634.5) J/cm3. Immediately after HIFU treatment, 1 patient (5.9%) achieved complete response (CR), 4 patients (23.5%) had a moderate response, 8 patients (47.1%) had partial reperfusion and 4 patients (23.5%) had stable disease (SD). The average ablation rate for all the tumors was 51.5 ± 26.7%. The level of glutamic-pyruvic transaminase (ALT) was mildly increased in 71.6% (12/17) of patients after HIFU therapy. Mean ALT values before and after treatment were 22 (14, 35) U/L and 36 (25, 41) U/L, respectively (Z = 1.947, p = 0.051). Mild or obvious edema in skin and subcutaneous soft tissues were observed in 76.5% of patients, but no serious side effects were found. Twelve months after treatment, the follow-up results revealed that 1 patient (5.8%) achieved a CR, 8 patients (47.1%) had SD and 8 patients (47.1%) had progressive disease. The estimated median time to progression was 11 mo after treatment, with a 95% confidence interval of 6, 11 for all involved patients.

CONCLUSION

Use of Sonazoid is safe and feasible for improving HIFU ablation efficiency during the treatment of advanced malignant liver lesions. The therapeutic efficacy of Sonazoid-assisted HIFU needs to be explored in additional controlled clinical investigations.

Assessing Enhanced Acoustic Absorption From Sonosensitive Perfluorocarbon Emulsion With Magnetic Resonance-Guided High-Intensity Focused Ultrasound and a Percolated Tissue-Mimicking Flow Phantom

OBJECTIVE

Sonosensitive high-boiling point perfluorocarbon F₈TAC₁₈-PFOB emulsions previously exhibited thermal enhancement during focused ultrasound heating in ex vivo pig livers, kidneys and a laminar flow phantom. The main objectives of this study were to evaluate heating under turbulent conditions, observe perfusion effects, quantify heating in terms of acoustic absorption and model the experimental data.

METHODS

In this study, similar perfluorocarbon emulsions were circulated at incremental concentrations of 0.07, 0.13, 0.19 and 0.25% v:v through a percolated turbulent flow phantom, more representative of the biological tissue than a laminar flow phantom. The concentrations represent the droplet content in only the perfused fluid, rather than the droplet concentration throughout the entire cross-section. The temperature was measured with magnetic resonance thermometry, during focused ultrasound sonications of 67 W, 95% duty cycle and 33 s duration. These were used in Bioheat equation simulations to investigate in silico the thermal phenomena. The temperature change was compared with the control condition by circulating de-gassed and de-ionized water through the flow phantom without droplets.

RESULTS

With these 1.24 µm diameter droplets at 0.25% v:v, the acoustic absorption coefficient increased from 0.93 ± 0.05 at 0.0% v:v to 1.82 ± 0.22 m^-1 at 0.25% v:v using a 0.1 mL s^-1 flow rate. Without perfusion at 0.25% v:v, an increase was observed from 1.23 ± 0.07 m^-1 at 0.0% v:v to 1.65 ± 0.17 m^-1.

CONCLUSION

The results further support previously reported thermal enhancement with F₈TAC₁₈-PFOB emulsion, quantified the increased absorption at small concentration intervals, illustrated that the effects can be observed in a variety of visceral tissue models and provided a method to simulate untested scenarios.

MR-guided ultrasound-stimulated microbubble therapy enhances radiation-induced tumor response

High intensity focused ultrasound (HIFU) systems have been approved for therapeutic ultrasound delivery to cause tissue ablation or induced hyperthermia. Microbubble agents have also been used in combination with sonication exposures. These require temperature feedback and monitoring to prevent unstable cavitation and prevent excess tissue heating. Previous work has utilized lower power and pressure to oscillate microbubbles and transfer energy to endothelial cells in the absence of thermally induced damage that can radiosensitize tumors. This work investigated whether reduced acoustic power and pressure on a commercial available MR-integrated HIFU system could result in enhanced radiation-induced tumor response after exposure to ultrasound-stimulated microbubbles (USMB) therapy. A commercially available MR-integrated HIFU system was used with a hyperthermia system calibration provided by the manufacturer. The ultrasound transducer was calibrated to reach a peak negative pressure of - 750 kPa. Thirty male New Zealand white rabbits bearing human derived PC3 tumors were grouped to receive no treatment, 14 min of USMB, 8 Gy of radiation in a separate irradiation cabinet, or combined treatments. In vivo temperature changes were collected using MR thermometry at the tumor center and far-field muscle region. Tissues specimens were collected 24 h post radiation therapy. Tumor cell death was measured and compared to untreated controls through hematoxylin and eosin staining and immunohistochemical analysis. The desired peak negative pressure of - 750 kPa used for previous USMB occurred at approximately an input power of 5 W. Temperature changes were limited to under 4 °C in ten of twelve rabbits monitored. The median temperature in the far-field muscle region of the leg was 2.50 °C for groups receiving USMB alone or in combination with radiation. Finally, statistically significant tumor cell death was demonstrated using immunohistochemical analysis in the combined therapy group compared to untreated controls. A commercial MR-guided therapy HIFU system was able to effectively treat PC3 tumors in a rabbit model using USMB therapy in combination with radiation exposures. Future work could find the use of reduced power and pressure levels in a commercial MR-guided therapy system to mechanically stimulate microbubbles and damage endothelial cells without requiring high thermal doses to elicit an antitumor response.

Application value of contrast-enhanced ultrasonography in the treatment of uterine fibroids by high-intensity focused ultrasound ablation: A retrospective study

PURPOSE

To determine efficacy and safety of contrast-enhanced ultrasonography (CEUS) in high-intensity focused ultrasound (HIFU) ablation of uterine fibroids (UFs).

METHODS

We retrospectively reviewed women undergoing HIFU ablation for UFs between June 2018 and January 2020. Before and after HIFU, patients underwent CEUS and magnetic resonance imaging (MRI) examinations. The relationship between CEUS features and ablation rate was analyzed. The time-intensity curves on CEUS were measured before and after HIFU ablation, and compared with those obtained using MRI. Adverse reactions were recorded.

RESULTS

A total of 64 patients were included. The immediate HIFU ablation rate significantly differed between low-, iso-, and high-enhancement UFs (87.2% ± 1.6%, 83.3% ± 2.1%, and 72.9% ± 3.1%, respectively; p < 0.05). On CEUS, the peak time of the time-intensity curve was significantly longer after treatment than before treatment (32.2 ± 9.7 and 26.7 ± 9.4 s, respectively; p < 0.05). Peak intensity was significantly lower after treatment than before treatment (13.7 ± 7.5 and 30.9 ± 11.2 dB, respectively; p < 0.05). All measurements were comparable between CEUS and MRI. The most common peri- and post-procedure adverse reaction was pain, which was temporary.

CONCLUSION

CEUS could dynamically and safely evaluate the immediate effects of the HIFU ablation of UFs.

PFOB sonosensitive microdroplets: determining their interaction radii with focused ultrasound using MR thermometry and a Gaussian convolution kernel computation

Purpose: Micron-sized perfluorocarbon droplet adjuvants to focused ultrasound therapies allow lower applied power, circumvent unwanted prefocal heating, and enhance thermal dose in highly perfused tissues. The heat enhancement has been shown to saturate at increasing concentrations. Experiments were performed to empirically model the saturating heating effects during focused ultrasound.Materials and methods: The measurements were made at varying concentrations using magnetic resonance thermometry and focused ultrasound by circulating droplets of mean diameter 1.9 to 2.3 µm through a perfused phantom. A simulation was performed to estimate the interaction radius size, empirically.Results: The interaction radius, representing the radius of a sphere encompassing 90% of the probability for the transformation of acoustic energy into heat deposition around a single droplet, was determined experimentally from ultrasonic absorption coefficient measurements The simulations suggest the interaction radius was approximately 12.5-fold larger than the geometrical radius of droplets, corresponding to an interaction volume on the order of 2000 larger than the geometrical volume.Conclusions: The results provide information regarding the dose-response relationship from the droplets, a measure with 15% precision of their interaction radii with focused ultrasound, and subsequent insights into the underlying physical heating mechanism.

Phase-shift Perfluoropentane Nanoemulsions Enhance Pulsed High-intensity Focused Ultrasound Ablation in an Isolated Perfused Liver System and Their Potential Value for Cancer Therapy

PURPOSE

To investigate whether phase-shift perfluoropetane (PFP) nanoemulsions can enhance pulsed high-intensity focused ultrasound (HIFU) ablation.

METHODS

PFP was encapsulated by poly(lactic-co-glycolic acid) (PLGA) to form a nanometer-sized droplet (PLGA-PFP), which was added to an isolated perfused liver system. Meanwhile, phosphate-buffered saline (PBS) was used as a control. The perfused liver was exposed to HIFU (150 W, t = 3/5/10 s) at various duty cycles (DCs). The ultrasound images, cavitation emissions, and temperature were recorded. Rabbits with subcutaneous VX2 tumors were exposed to HIFU (150 W) at various DCs with or without PLGA-PFP. After ablation, necrosis volume and energy efficiency factor were calculated. Pathologic characteristics were observed.

RESULTS

Compared to the PBS control, PLGA-PFP nanoemulsions markedly enhanced HIFU-induced necrosis volume in both perfused livers and subcutaneous VX2 tumor-bearing rabbits (P <.05). Inertial cavitation was much stronger in the pulsed-HIFU exposure at 10% than that in the continuous-wave HIFU exposure (P <.01). Peak temperature at 100% DC was significantly higher than that at 10% (P <.05). Compared to 100% DC HIFU exposure, the mean necrosis volume induced by 10 s exposure at 50% DC was significantly larger (P <.005) but lower at 10% DC in the isolated perfused livers (P <.05). In addition, the mean necrosis volume in subcutaneous VX2 tumor-bearing rabbits was significantly increased after HIFU exposure at 10% DC when compared to those at 100% DC (P <.05). Histopathologic analysis showed liquefaction necrosis in pulsed HIFU.

CONCLUSION

PLGA-PFP nanoemulsions can enhance HIFU ablation in the isolated perfused livers and promote tumor ablation in the subcutaneous xenograft rabbit model. Appropriate pulsed HIFU exposure may increase the necrosis volume and reduce total ultrasound energy required for HIFU ablation.

Contrast-Enhanced Ultrasound Imaging of Uterine Disorders: A Systematic Review

Uterine disorders are often presented with overlapping symptoms. The microvasculature holds specific information important for diagnosing uterine disorders. Conventional sonography is an established diagnostic technique in gynecology, but is limited by its inability to image the microvasculature. Contrast-enhanced ultrasound (CEUS), is capable of imaging the microvasculature by means of intravascular contrast agents; that is, gas-filled microbubbles. We provide a literature overview on the use of CEUS in diagnosing myometrial and endometrial disorders, that is, fibroids, adenomyosis, leiomyosarcomas and endometrial carcinomas, as well as for monitoring and enhancing the effectiveness of minimally invasive therapies. A systematic literature search with quality assessment was performed until December 2020. In total 34 studies were included, published between 2007 and 2020.The results entail a description of contrast-enhancement patterns obtained from healthy tissue and from malignant and benign tissue; providing a first base for potential diagnostic differentiation in gynecology. In addition it is also possible to determine the degree of myometrial invasion in case of endometrial carcinoma using CEUS. The effectiveness of minimally invasive therapies for uterine disorders can safely and accurately be assessed with CEUS. In conclusion, the abovementioned applications of CEUS are promising and it is worth further exploring its full potential for gynecology by designing innovative and methodologically high-quality clinical studies.

Comparison of outcomes of hysteroscopic myomectomy of type 2 submucous fibroids greater than 4 cm in diameter via pretreatment with HIFU or GnRH-a

OBJECTIVE

To compare the efficacy and safety of high-intensity focused ultrasound (HIFU) and gonadotropin-releasing analogues (GnRH-a) as pretreatments for the hysteroscopic transcervical resection of myoma (TCRM) for type 2 submucosal fibroids greater than 4 centimeters in diameter.

MATERIALS AND METHODS

Seventy-nine patients were assigned into two groups according patient preference: 42 in HIFU and 37 in GnRHa. TCRM was performed after 3 months of pretreatment with HIFU or GnRHa.

RESULTS

Following pretreatment with HIFU or GnRHa, uterine-fibroid symptom (UFS) scores and hemoglobin levels (HGB) showed improvement. The fibroid maximum diameter, size of fibroids, and volume of the uterus were decreased. Following HIFU pretreatment, one case reported complete vaginal fibroid expulsion, and four reported partial fibroid expulsion. No similar cases were found in the GnRHa group. Eighteen patients were lost to follow-up prior to TCRM. Among the 31 patients in HIFU, the fibroids were downgraded to type 0 in 10 cases and type 1 in 5 cases. Of the 30 patients in GnRHa, the treated fibroids were downgraded to type 1 in 9 cases. The mean operation time and intraoperative blood loss of the HIFU group were significantly lower than those in the GnRHa group. No significant differences were observed in the incidence of intraoperative complications and the one-time resection rate of fibroids between the two groups (p>.05).

CONCLUSIONS

HIFU seems to be superior to GnRHa as a pretreatment method prior to TCRM for type 2 submucosal fibroids greater than 4 centimeters in diameter.

[Preparation of doxorubicin-loaded metallic organic nanoparticles and their effect for enhancing efficacy of high-intensity focused ultrasound therapy in tumor-bearing mice]

OBJECTIVE

To prepare metallic organic nanoparticles that produce synergistic effect in high-intensity focused ultrasound (HIFU) therapy of tumors.

OBJECTIVE

Glucose oxidase (GOD), MnO₂, ferric iron (Fe³⁺) and doxorubicin (DOX) were self-assembled by physical adsorption with previously prepared manganese dioxide (MnO₂) nanoparticles to obtain GOD-MnO₂-Fe³⁺-DOX nanoparticles (GMFD NPs). HepG2 tumor-bearing nude mouse models were given intravenous injections of normal saline or GMFD NPs followed 4 h later by HIFU at the acoustic power of 90 W with a total treatment time of 3 s. The changes of tumor gray value before and after HIFU irradiation were observed and 24 h after HIFU irradiation, coagulation necrosis in the tumor tissues was examined; the histological changes of the tumor tissues were observed with HE staining.

OBJECTIVE

We successfully prepared GMFD NPs, which had an average particle size of 131.23±0.84 nm with a surface potential of 21.87±1.72 mV. GMFD NPs, with a drug loading rate of 40.18%, was capable of releasing more than 77.2% of the loaded DOX within 4 h in acidic environment. In the tumor-bearing mouse models, HIFU irradiation following GMFD NP injection, as compared with saline injection, resulted in significantly enhanced gray value of the tumor (25.5±4.5 vs 18.7±3.9, P=0.04) and greater volume of coagulation necrosis (105.80 ± 1.21 mm³ vs 38.02 ± 0.34 mm³). The energy efficiency factor (EEF) was significantly lower in GMFD NPs group than in saline group (1.79 vs 4.97, P < 0.001).

OBJECTIVE

GMFD NPs prepared in this study can enhance tumor ablation efficacy of HIFU and release DOX for further treatment of the residual tumor tissue in mice.

Nanobiotechnology-enabled energy utilization elevation for augmenting minimally-invasive and noninvasive oncology thermal ablation

Depending on the local or targeted treatment, independence on tumor type and minimally-invasive and noninvasive feature, various thermal ablation technologies have been established, but they still suffer from the intractable paradox between safety and efficacy. It has been extensively accepted that improving energy utilization efficiency is the primary means of decreasing thermal ablation power and shortening ablation time, which is beneficial for concurrently improving both treatment safety and treatment efficiency. Recent efforts have been made to receive a significant advance in various thermal methods including non-invasive high-intensity focused ultrasound, minimally-invasive radiofrequency and microwave, and non-invasive and minimally-invasive photothermal ablation, and so on. Especially, various nanobiotechnologies and design methodologies were employed to elevate the energy utilization efficiency for acquiring unexpected ablation outcomes accompanied with tremendously reduced power and time. More significantly, some combined technologies, for example, chemotherapy, photodynamic therapy (PDT), gaseous therapy, sonodynamic therapy (SDT), immunotherapy, chemodynamic therapy (CDT), or catalytic nanomedicine, were used to assist these ablation means to repress or completely remove tumors. We discussed and summarized the ablation principles and energy transformation pathways of the four ablation means, and reviewed and commented the progress in this field including newly developed technology or new material types with a highlight on nanobiotechnology-inspired design principles, and provided the deep insights into the existing problems and development direction. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Emerging Technologies.

The safety of echo contrast-enhanced ultrasound in high-intensity focused ultrasound ablation for abdominal wall endometriosis: a retrospective study

Background

We aimed to investigate the efficacy and safety of echo contrast-enhanced ultrasound (CEUS) during high-intensity focused ultrasound (HIFU) ablation therapy for abdominal wall endometriosis (AWE).

Methods

A total of 67 patients with AWE were treated with HIFU ablation, and their demographic characteristics were retrospectively analysed. Blood perfusion of the focal lesion was assessed before the operation, during ablation and after the operation with the use of an ultrasound contrast agent, and the effect of the ultrasound contrast agent on treatment was assessed over a 1-year follow-up period. The degree of symptom relief and adverse effects were evaluated after HIFU ablation.

Results

Eighty-two lesions were ablated in 67 patients. CEUS showed that all lesions were successfully ablated with HIFU. The shrinkage ratio of the lesions significantly increased over the follow-up period. Intermittent pain disappeared at 1 month after the operation, and the patients' pain scores significantly decreased at the 1-year follow-up. The mean [± standard deviation (SD)] lesion volume was 7.64±8.95 cm³ on B-mode ultrasound. The post-HIFU non-perfused volume was 18.34±24.08 cm³, and the rate of massive changes on greyscale imaging was 96.16%±5.44% at 12 months. During the procedure, the main complications were a prickling sensation and tenderness in the treatment area and/or a transient "hot" sensation on the skin. After the procedure, there was no obvious discomfort except for pain. Two patients developed an approximately 1-cm area of skin that exhibited a waxy appearance. Seven patients had haematuria. No severe complications were observed.

Conclusions

Ultrasound contrast agents are effective and safe for evaluating the effect of HIFU ablation on AWE, and this approach provides significant guidance and evaluation benefits for the use of HIFU treatment for AWE without obvious side effects.

Comparative Effectiveness and Safety of High-Intensity Focused Ultrasound for Uterine Fibroids: A Systematic Review and Meta-Analysis

Background: Uterine fibroids are common benign tumors among premenopausal women. High- intensity focused ultrasound (HIFU) is an emerging non-invasive intervention which uses the high-intensity ultrasound waves from ultrasound probes to focus on the targeted fibroids. However, the efficacy of HIFU in comparison with that of other common treatment types in clinical procedure remains unclear.

Objective: To investigate the comparative effectiveness and safety of HIFU with other techniques which have been widely used in clinical settings.

Methods: We searched the Cochrane Central Register of Controlled Trials, PubMed, EMBASE, Cumulative Index to Nursing & Allied Health Literature, Web of Science, ProQuest Nursing & Allied Health Database, and three Chinese academic databases, including randomized controlled trials (RCTs), non-RCTs, and cohort studies. The primary outcome was the rate of re-intervention, and the GRADE approach was used to interpret the findings.

Results: About 18 studies met the inclusion criteria. HIFU was associated with an increased risk of re-intervention rate in comparison with myomectomy (MYO) [pooled odds ratio (OR): 4.05, 95% confidence interval (CI): 1.82–8.9]. The results favored HIFU in comparison with hysterectomy (HYS) on the change of follicle-stimulating hormone [pooled mean difference (MD): −7.95, 95% CI: −8.92–6.98), luteinizing hormone (MD: −4.38, 95% CI: −5.17−3.59), and estradiol (pooled MD: 43.82, 95% CI: 36.92–50.72)]. HIFU had a shorter duration of hospital stay in comparison with MYO (pooled MD: −4.70, 95% CI: −7.46−1.94, p < 0.01). It had a lower incidence of fever (pooled OR: 0.15, 95% CI: 0.06–0.39, p < 0.01) and a lower incidence of major adverse events (pooled OR: 0.04, 95% CI: 0.00–0.30, p < 0.01) in comparison with HYS.

Conclusions: High-intensity focused ultrasound may help maintain feminity and shorten the duration of hospital stay. High-quality clinical studies with a large sample size, a long-term follow-up, and the newest HIFU treatment protocol for evaluating the re-intervention rate are suggested to be carried out. Clinical decision should be based on the specific situation of the patients and individual values.

Contrast-Enhanced Ultrasound for Monitoring Non-surgical Treatments of Uterine Fibroids: A Systematic Review

Non-surgical treatment options for uterine fibroids are uterine artery embolization (UAE), high-intensity focused ultrasound ablation (HIFUA), and percutaneous microwave ablation (PMWA). Magnetic resonance imaging (MRI) is the reference standard imaging method before and after these procedures. Contrast-enhanced ultrasound (CEUS) has been studied as an alternative to MRI for evaluating the fibroids' characteristics and responses to non-surgical treatments. PubMed, Ovid MEDLINE and Scopus databases were searched for literature published from January 2000 through June 7, 2020, that investigated the application of CEUS as an adjunct to monitor UAE, HIFUA or PMWA in human uterine fibroid treatments. Two independent reviewers analyzed 128 publications, out of which 17 were included. Based on this systematic review, CEUS provides detailed data about fibroid volume and vascularization prior, during and post UAE, and it helps determine the endpoint of the procedure. HIFUA with intra-procedural CEUS has faster volume shrinkage over a shorter time period with less needed energy and provides early detection of residual tissue after HIFUA. CEUS and contrast-enhanced MRI have sufficient agreement to be used interchangeably in the clinic to evaluate the therapeutic effect of PMWA and HIFUA on fibroids.

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.

Enhancement of HIFU ablation by sonosensitizer-loading liquid fluorocarbon nanoparticles with pre-targeting in a mouse model

High intensity focused ultrasound (HIFU) is a noninvasive thermal ablation technique for the treatment of benign and malignant solid masses. To improve the efficacy of HIFU ablation, we developed poly (lactide-co-glycolide) (PLGA) nanoparticles encapsulating perfluoropentane (PFP) and hematoporphyrin monomethyl ether (HMME) as synergistic agents (HMME+PFP/PLGA). Two-step biotin-avidin pre-targeting technique was applied for the HIFU ablation. We further modified the nanoparticles with streptavidin (HMME+PFP/PLGA-SA). HMME+PFP/PLGA-SA were highly dispersed with spherical morphology (477.8 ± 81.8 nm in diameter). The encapsulation efficiency of HMME and PFP were 46.6 ± 3.3% and 40.1 ± 2.6%, respectively. The binding efficiency of nanoparticles to streptavidin was 95.5 ± 2.5%. The targeting ability of the HMME+PFP/PLGA-SA nanoparticles was tested by parallel plate flow chamber in vitro. In the pre-targeting group (HMME+PFP/PLGA-SA), a large number of nanoparticles bound to the peripheral and surface of the cell. In the HIFU ablation experiment in vivo, compared with the other groups, the largest gray-scale changes and coagulation necrosis areas were observed in the pre-targeting (HMME+PFP/PLGA-SA) group, with the lowest energy efficiency factor value. Moreover, the microvessel density and proliferation index declined, while the apoptotic index increased, in the tumor tissue surrounding the coagulation necrosis area in the pre-targeting group. Meanwhile, the survival time of the tumor-bearing nude mice in the pre-targeting group was significantly longer than that in the HIFU treatment group. These results suggest that HMME+PFP/PLGA-SA have high potential to act as synergistic agents in HIFU ablation.