Enhancing ablation effects of a microbubble-enhancing contrast agent ("SonoVue") in the treatment of uterine fibroids with high-intensity focused ultrasound: a randomized controlled trial

Ultrasound Contrast Agents: Current Role in Adults and Children for Various Indications

Intravenous contrast-enhanced ultrasound (CEUS) is a rapidly evolving imaging technique that uses a microbubble contrast agent to enhance ultrasonographic images by augmenting characterization of blood vessels and organ perfusion. CEUS is considered as a useful problem-solving tool and as an indicated first-line imaging modality in select settings. CEUS technique has an inherent advantage over its predecessor B-mode and Doppler imaging. This article reviews different approved and off-label use of CEUS in the pediatric and adult population and also discusses Food and Drug Administration-approved contrast agents in the United States, their reported side effects, and ongoing efforts in the field.

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.

Role of ultrasonography in the evaluation of disease severity and treatment efficacy in adenomyosis

BACKGROUND

Adenomyosis is a benign disorder characterized by the presence of ectopic endometrial glands and stroma within the myometrium. The main clinical manifestations of adenomyosis are dysmenorrhea, menorrhagia, and infertility, which affect patients' quality of life. Recently, with advancements in imaging techniques, magnetic resonance imaging, and ultrasonography have become the main diagnostic tools for adenomyosis. In addition to the diagnosis and differential diagnosis of adenomyosis, ultrasonography can also be used to evaluate the severity of adenomyosis. The emergence of new techniques, such as elastography and contrast-enhanced ultrasonography (CEUS), has significantly improved the accuracy of ultrasound-based diagnosis of adenomyosis. These two imaging tools can also be used for the differential diagnosis of adenomyosis and the evaluation of treatment efficacy after medication or ablation procedure.

OBJECTIVE

we review the efficacy of ultrasonography as a diagnostic tool for adenomyosis. We also aim to introduce the potential of ultrasound imaging in the evaluation of the severity of this disease, as well as the application of elastography and contrast-enhanced ultrasonography (CEUS) in its diagnosis.

RESULTS AND CONCLUSION

Our findings reveal the potential value of ultrasonography combined with elastography and/or CEUS as medication guidance and efficacy evaluation tools in the long-term management of adenomyosis.

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.

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.

Microbubble contrast agent SonoVue combined with oxytocin improves the efficiency of high-intensity focused ultrasound ablation for adenomyosis

BACKGROUND

To investigate the combined enhancing effects of microbubble-contrast SonoVue and oxytocin on high-intensity focused ultrasound (HIFU) ablation of adenomyosis.

METHODS

330 patients with adenomyosis were randomly assigned to SonoVue and oxytocin group (group A, n = 82), oxytocin (group B, n = 85), SonoVue (group C, n = 81), or the control (group D, n = 82) for HIFU ablation. In group A, oxytocin was dripped 0.32 IU/min, and HIFU ablation was started one minute after SonoVue injection. In group B, oxytocin was dripped 0.32 IU/min during ablation. In group C, HIFU ablation was started one minute after SonoVue injection. In group D, neither oxytocin nor SonoVue was applied. The clinical data, treatment results, and complications were analyzed.

RESULTS

All participants underwent HIFU treatment safely, and the mean energy efficiency factor (EEF) in the four groups was 4.7 ± 0.9J/mm³, 8.5 ± 0.6J/mm³, 8.9 ± 0.7J/mm³, and 12.6 ± 1.8J/mm³, respectively, with the mean ablation time (AT) of 633.7 ± 55.1 s, 874.2 ± 65.6 s, 936.3 ± 85.2 s, and 1103.2 ± 96.2 s, respectively. The non-perfused volume ratios (NPVR) were 90.4 ± 8.8%, 88.7 ± 9.1%, 89.4 ± 7.2%, 80.5 ± 7.9%, respectively. In addition, EEF and AT were the shortest in group A (p < 0.05). NPVR was significantly higher in group A than in the control group D (p < 0.05). The incidence rates of adverse events were not significantly different in the four groups (p > 0.05).

CONCLUSIONS

Compared to the control group, oxytocin combined with SonoVue in HIFU for adenomyosis can significantly decrease the energy and time needed for the ablation and safely enhance the treatment efficiency by improving the cavitation and heating of HIFU ablation and increasing the non-perfused volume ratio.

Contrast-Enhanced Ultrasonography: Review and Applications

Contrast-enhanced ultrasound (CEUS) has revolutionized ultrasound imaging adding enhanced diagnostic imaging and therapeutic applications to its repertoire. CEUS involves the use of microbubbles which are lauded for their benefit of enhanced imaging without the limitations of radiation exposure or risk of nephrotoxicity seen with other contrast agents. In addition, many innovative uses of microbubbles in diagnosis and treatment stages have been discovered. This article summarizes the composition and resonance properties of microbubbles as the contrast agents for ultrasound, as well as their advanced uses in medicine. The basic role of CEUS is in enhancing the imaging of vessels on a macro and micro level to better classify pathological lesions like atherosclerosis. CEUS is also used in identifying tumor lesions by observing for angiogenesis and monitoring tumors post treatment for remission and relapses. Recent research on using microbubbles for focused drug delivery is very promising. Microbubbles can be used for thrombolysis and targeted delivery of chemotherapeutics in an efficient targeted manner while limiting systemic side effects. CEUS can also be used with therapeutic and diagnostic agents to penetrate into the brain allowing better assessment and management of neurodegenerative disorders. In conclusion, the use of microbubbles opens new frontiers in diagnosis and treatment and will likely be a key technique in medicine in the near future.

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.

Comprehensive review on ultrasound-responsive theranostic nanomaterials: mechanisms, structures and medical applications

The field of theranostics has been rapidly growing in recent years and nanotechnology has played a major role in this growth. Nanomaterials can be constructed to respond to a variety of different stimuli which can be internal (enzyme activity, redox potential, pH changes, temperature changes) or external (light, heat, magnetic fields, ultrasound). Theranostic nanomaterials can respond by producing an imaging signal and/or a therapeutic effect, which frequently involves cell death. Since ultrasound (US) is already well established as a clinical imaging modality, it is attractive to combine it with rationally designed nanoparticles for theranostics. The mechanisms of US interactions include cavitation microbubbles (MBs), acoustic droplet vaporization, acoustic radiation force, localized thermal effects, reactive oxygen species generation, sonoluminescence, and sonoporation. These effects can result in the release of encapsulated drugs or genes at the site of interest as well as cell death and considerable image enhancement. The present review discusses US-responsive theranostic nanomaterials under the following categories: MBs, micelles, liposomes (conventional and echogenic), niosomes, nanoemulsions, polymeric nanoparticles, chitosan nanocapsules, dendrimers, hydrogels, nanogels, gold nanoparticles, titania nanostructures, carbon nanostructures, mesoporous silica nanoparticles, fuel-free nano/micromotors.

Evaluation of Pseudorandom Sonications for Reducing Cavitation With a Clinical Neurosurgery HIFU Device

Transcranial high-intensity focused ultrasound is used in clinics for treating essential tremor (ET) and proposed for many other brain disorders. This promising treatment modality requires high energy resulting eventually in undesired cavitation and potential side effects. The goals of the present work were: 1) to evaluate the potential increase of the cavitation threshold using pseudorandom gated sonications and 2) to assess the heating capabilities with such sonications. The experiments were performed with the transcranial magnetic resonance (MR)-compatible ExAblate Neuro system (InSightec, Haifa, Israel) operating at a frequency of 670 kHz, either in continuous wave (CW) or with pseudorandom gated sonications of 50% duty cycle. Cavitation activity with the two types of sonications was compared using chemical dosimetry of hydroxyl radical production at the focus of the transducer, after propagation in water or through a human skull. Heating trials were performed in a hydrogel tissue-mimicking material embedded in a human skull to mimic a clinical situation. The temperature was measured by MR-thermometry when focusing at the geometrical focus and steering off focus up to 15 mm. Compared with CW sonications, the use of gated sonication did not affect the efficiency (60%) nor the steering abilities of the transducer. After propagation through a human skull, gated sonication required a higher pressure level (10 MPa) to initiate cavitation as compared with CW (5.8 MPa). Moreover, at equivalent acoustic power above the cavitation threshold, the level of cavitation activity initiated with gated sonications was much lower with gated sonication than with continuous sonications, almost half after propagation through water and one-third after propagation through a skull. This lowered cavitation activity may be attributed to a breaking of the dynamic of the bubbles moving from monochromatic to more broadband sonications and to the removal of residual cavitation nuclei between pulses with gated sonications. The heating capability was not affected by the gated sonications, and similar temperature increases were reached at focus with both types of sonications when sonicating at equivalent acoustic power, both in water or after propagation through a human skull (+15 °C at 325 W for 10 s). These data, acquired with a clinical system, suggest that gated sonication could be an alternative to continuous sonications when cavitation onset is an issue.

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.

Functional micro/nanobubbles for ultrasound medicine and visualizable guidance

Chemically functionalized gas-filled bubbles with a versatile micro/nano-sized scale have witnessed a long history of developments and emerging applications in disease diagnosis and treatments. In combination with ultrasound and image-guidance, micro/nanobubbles have been endowed with the capabilities of biomedical imaging, drug delivery, gene transfection and disease-oriented therapy. As an external stimulus, ultrasound (US)-mediated targeting treatments have been achieving unprecedented efficiency. Nowadays, US is playing a crucial role in visualizing biological/pathological changes in lives as a reliable imaging technique and a powerful therapeutic tool. This review retrospects the history of ultrasound, the chemistry of functionalized agents and summarizes recent advancements of functional micro/nanobubbles as US contrast agents in preclinical and transclinical research. Latest ultrasound-based treatment modalities in association with functional micro/nanobubbles have been highlighted as their great potentials for disease precision therapy. It is believed that these state-of-the-art micro/nanobubbles will become a booster for ultrasound medicine and visualizable guidance to serve future human healthcare in a more comprehensive and practical manner.

Clinical significance of performing Sonazoid-based contrast-enhanced ultrasonography before ablation of uterine fibroids by high-intensity focused ultrasound: A preliminary cohort study

High-intensity focused ultrasound (HIFU) is effective for the ablation of uterine fibroids. However, no research has indicated whether HIFU ablation of uterine fibroids might be improved by application of contrast-enhanced ultrasonography (CEUS) with Sonazoid as a contrast agent. This study aimed to assess the clinical significance of Sonazoid-based CEUS 30 minute before HIFU ablation of uterine fibroids.This retrospective cohort study included Asian patients with solitary uterine fibroids who were treated with HIFU at Seoul HICARE Clinic (South Korea; n = 34) and the Second Affiliated Hospital of Chongqing Medical University (China; n = 30) between August 1, 2017, and October 31, 2017. The patients in Seoul underwent Sonazoid-based CEUS 30 minute before HIFU. All the patients received contrast-enhanced magnetic resonance imaging to diagnose uterine fibroids. The ablation results were evaluated 1 day after HIFU by contrast-enhanced magnetic resonance imaging or Sonazoid-based CEUS.All the patients were successfully treated with HIFU. The CEUS+HIFU group had lower values for sonication power, treatment time, sonication time, total energy applied, and energy efficiency factor compared with HIFU alone group (P < .001). There were no major adverse events after ablation therapy in either group. The incidence of post-procedure sacrococcygeal pain was lower in the CEUS+HIFU group than that in the HIFU alone group (P = .045), while the incidences of all other intraoperative and postoperative adverse events were similar between the 2 groups.Our findings suggest that Sonazoid-based CEUS before HIFU may enhance the ablation of uterine fibroids.

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.

Nanoparticle-Coated Microbubbles for Combined Ultrasound Imaging and Drug Delivery

Biomedical microbubbles stabilized by a coating of magnetic or drug-containing nanoparticles show great potential for theranostics applications. Nanoparticle-coated microbubbles can be made to be stable, to be echogenic, and to release the cargo of drug-containing nanoparticles with an ultrasound trigger. This Article reviews the design principles of nanoparticle-coated microbubbles for ultrasound imaging and drug delivery, with a particular focus on the physical chemistry of nanoparticle-coated interfaces; the formation, stability, and dynamics of nanoparticle-coated bubbles; and the conditions for controlled nanoparticle release in ultrasound. The emerging understanding of the modes of nanoparticle expulsion and of the transport of expelled material by microbubble-induced flow is paving the way toward more efficient nanoparticle-mediated drug delivery. This Article highlights the knowledge gap that still remains to be addressed before we can control these phenomena.

Clinical Usefulness of the Microbubble Contrast Agent SonoVue in Enhancing the Effects of High-Intensity Focused Ultrasound for the Treatment of Adenomyosis

OBJECTIVE

To evaluate the clinical usefulness of the microbubble contrast agent SonoVue in enhancing high-intensity focused ultrasound (HIFU) for the treatment of adenomyosis.

METHODS

A total of 102 patients with adenomyosis, assessed from August 2015 to April 2017, were randomly divided into 1-minute (A) and 10-minute (B) groups, respectively. In groups A and B, HIFU started 1 minute and 10 minutes, respectively, after SonoVue injection. All patients underwent a magnetic resonance imaging scan before and after HIFU treatment.

RESULTS

The occurrence rates of massive gray scale change, nonperfused volume, and fractional ablation were similar in both groups (P > .05). Meanwhile, sonication time to massive gray scale change was reduced in group A compared with group B (P < .05). In addition, mean power, total energy, and energy efficiency factor were lower in group A than group B (all P < .05). The incidence rates of most perioperative and all postoperative adverse events were similar in both groups (P > .05). The incidence rates of pain in the treated region, leg pain, and sciatic or buttock pain during HIFU were substantially lower in group A than group B (P < .05).

CONCLUSIONS

Overall, starting HIFU sonication at 1 minute after SonoVue injection enhances HIFU ablation by cavitation and heating and is safe. Early massive gray scale change, lower total energy, and reduced mean power are potential safety factors.

Application of contrast-enhanced ultrasound and enhanced CT in diagnosis of liver cancer and evaluation of radiofrequency ablation

This study investigated the application effect of contrast-enhanced ultrasound (CEUS) and enhanced CT in diagnosis of liver cancer and response evaluation of radiofrequency ablation (RFA). A total of 60 patients with liver cancer were selected in Dongying People's Hospital from April 2016 to May 2017. All patients were subjected to CEUS and enhanced CT. With pathological examination as the gold standard, diagnostic consistency of the two methods was compared. After RFA, patients were subjected to CEUS and enhanced CT to assess the efficacy, and the consistency was compared. There was no significant difference in diagnostic accuracy between CEUS and CT (p>0.05). Area under the ROC curve of CEUS was 0.896, with a sensitivity of 91.2% and a specificity of 88.7%. The area under the ROC curve for enhanced CT diagnosis was 0.907, with a sensitivity of 91.8% and a specificity of 89.7%. No significant difference in the maximal cross sectional area of lesions was found between CEUS and enhanced CT, and there was no significant difference in evaluation of therapeutic efficiency between the methods (p>0.05) before and 1 and 3 months after treatment. Bland-Altman test showed that there was a strong consistency between CEUS and enhanced CT in the measured maximum cross-sectional area of lesions at 1 and 3 months after treatment. Linear regression analysis showed that maximum section cross-sectional area measured by CEUS was significantly correlated with that detected by enhanced CT (r²=0.617). The results suggested that diagnostic efficiency of CEUS was similar to that of enhanced CT, and both showed high sensitivity and specificity. Two methods showed high consistency in evaluating the curative effect of RFA. CEUS can achieve real-time observation of focal blood flow perfusion, and was more economically affordable and convenient.

Imaging with ultrasound contrast agents: current status and future

Microbubble ultrasound contrast agents (UCAs) were recently approved by the Food and Drug administration for non-cardiac imaging. The physical principles of UCAs, methods of administration, dosage, adverse effects, and imaging techniques both current and future are described. UCAs consist of microbubbles in suspension which strongly interact with the ultrasound beam and are readily detectable by ultrasound imaging systems. They are confined to the blood pool when administered intravenously, unlike iodinated and gadolinium contrast agents. UCAs have a proven safety record based on over two decades of use, during which they have been used in echocardiography in the U.S. and for non-cardiac imaging in the rest of the world. Adverse effects are less common with UCAs than CT/MR contrast agents. Compared to CT and MR, contrast-enhanced ultrasound has the advantages of real-time imaging, portability, and reduced susceptibility to metal and motion artifact. UCAs are not nephrotoxic and can be used in renal failure. High acoustic amplitudes can cause microbubbles to fragment in a manner that can result in short-term increases in capillary permeability or capillary rupture. These bioeffects can be beneficial and have been used to enhance drug delivery under appropriate conditions. Imaging with a mechanical index of < 0.4 preserves the microbubbles and is not typically associated with substantial bioeffects. Molecularly targeted ultrasound contrast agents are created by conjugating the microbubble shell with a peptide, antibody, or other ligand designed to target an endothelial biomarker associated with tumor angiogenesis or inflammation. These microbubbles then accumulate in the microvasculature at target sites where they can be imaged. Ultrasound contrast agents are a valuable addition to the diagnostic imaging toolkit. They will facilitate cross-sectional abdominal imaging in situations where contrast-enhanced CT and MR are contraindicated or impractical.

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

OBJECTIVE

To investigate the effects of a microbubble ultrasound contrast agent on high-intensity focused ultrasound (HIFU) treatment of uterine fibroids.

METHODS

A total of 120 patients with solitary uterine fibroid were randomly assigned into Groups A, B, C and D. Patients in Groups A and B received 1.5 ml of SonoVue, Groups C and D received 1.5 ml of saline before HIFU ablation. HIFU sonication started at 6 min after administration of SonoVue or saline in Groups A and C, whereas it started at 10 min in Groups B and D. On day 1 after HIFU, magnetic resonance imaging was performed. Patients were followed up via phone or clinic visit during the first week after HIFU.

RESULTS

No significant difference was observed in terms of age, fibroid location, diameter of fibroids, signal intensity on T2-weighted imaging, or tumour volume among the four groups (p > 0.05). The use of SonoVue significantly shortened the treatment time and sonication time. The sonication start time of 6 min, relative to 10 min, had significant effects on the treatment time and sonication time. The use of intravenous SonoVue followed by HIFU ablation 6 min later significantly increased the rate of significant grey-scale changes (55.9%) and the non-perfused volume ratio (94.2% ± 10.6%). No significant differences were observed in the incidence of intra-procedure and post-HIFU adverse effects among the four groups (p > 0.05).

CONCLUSIONS

SonoVue could be safely used to enhance the ablation effects of HIFU treatment of uterine fibroids.

Using microbubble sonographic contrast agent to enhance the effect of high intensity focused ultrasound for the treatment of uterine fibroids

OBJECTIVE

To evaluate the effects of the ultrasound contrast agent SonoVue in enhancing the ablative effects of Ultrasound-Guided high-intensity focused ultrasound (HIFU) on different sub-types of uterine fibroids.

MATERIALS AND METHODS

In this study, 390 fibroids from 319 patients were retrospectively evaluated, among which 155 were treated with SonoVue and 235 were without SonoVue during HIFU ablation. The efficacy of HIFU was evaluated using magnetic resonance scanning (MRI) in all patients.

RESULTS

The total ablation time to achieve the same non-perfused volume was significantly shortened with SonoVue. The average energy used and the acoustic energy for treating 1 mm(3) (EEF) was less when SonoVue is used as enhancing agent. The non-perfused volume (NPV) was measured by post-HIFU MRI and the mean fractional ablation was calculated. Mean NPV was 74% (range: 15%-100%) in the HIFU-only group and 75% (range: 17%-100%) in the HIFU+ SonoVue group. However, for T2 MRI low intensity signal fibroids, NPV in the SonoVue group reached 83% (range: 20%-100%) that was significantly higher than in the HIFU-only group, which was 76% (range: 15%-100%). No differences in adverse events were observed between the two groups.

CONCLUSIONS

Our observations demonstrate that the use of therapeutic SonoVue during the HIFU procedure can significantly decrease the ablation time and the energy requirement for the treatment of the same fibroid volume in all types of fibroids.

Evolution of contrast agents for ultrasound imaging and ultrasound-mediated drug delivery

Ultrasound (US) is one of the most frequently used diagnostic methods. It is a non-invasive, comparably inexpensive imaging method with a broad spectrum of applications, which can be increased even more by using bubbles as contrast agents (CAs). There are various different types of bubbles: filled with different gases, composed of soft- or hard-shell materials, and ranging in size from nano- to micrometers. These intravascular CAs enable functional analyses, e.g., to acquire organ perfusion in real-time. Molecular analyses are achieved by coupling specific ligands to the bubbles' shell, which bind to marker molecules in the area of interest. Bubbles can also be loaded with or attached to drugs, peptides or genes and can be destroyed by US pulses to locally release the entrapped agent. Recent studies show that US CAs are also valuable tools in hyperthermia-induced ablation therapy of tumors, or can increase cellular uptake of locally released drugs by enhancing membrane permeability. This review summarizes important steps in the development of US CAs and introduces the current clinical applications of contrast-enhanced US. Additionally, an overview of the recent developments in US probe design for functional and molecular diagnosis as well as for drug delivery is given.

Modeling and predicting tissue movement and deformation for high intensity focused ultrasound therapy

Purpose

In ultrasound-guided High Intensity Focused Ultrasound (HIFU) therapy, the target tissue (such as a tumor) often moves and/or deforms in response to an external force. This problem creates difficulties in treating patients and can lead to the destruction of normal tissue. In order to solve this problem, we present a novel method to model and predict the movement and deformation of the target tissue during ultrasound-guided HIFU therapy.

Methods

Our method computationally predicts the position of the target tissue under external force. This prediction allows appropriate adjustments in the focal region during the application of HIFU so that the treatment head is kept aligned with the diseased tissue through the course of therapy. To accomplish this goal, we utilize the cow tissue as the experimental target tissue to collect spatial sequences of ultrasound images using the HIFU equipment. A Geodesic Localized Chan-Vese (GLCV) model is developed to segment the target tissue images. A 3D target tissue model is built based on the segmented results. A versatile particle framework is constructed based on Smoothed Particle Hydrodynamics (SPH) to model the movement and deformation of the target tissue. Further, an iterative parameter estimation algorithm is utilized to determine the essential parameters of the versatile particle framework. Finally, the versatile particle framework with the determined parameters is used to estimate the movement and deformation of the target tissue.

Results

To validate our method, we compare the predicted contours with the ground truth contours. We found that the lowest, highest and average Dice Similarity Coefficient (DSC) values between predicted and ground truth contours were, respectively, 0.9615, 0.9770 and 0.9697.

Conclusion

Our experimental result indicates that the proposed method can effectively predict the dynamic contours of the moving and deforming tissue during ultrasound-guided HIFU therapy.

Contrast-enhanced ultrasound for evaluation of high-intensity focused ultrasound treatment of benign uterine diseases: retrospective analysis of contrast safety

As a noninvasive treatment technique, ultrasound-guided high-intensity focused ultrasound (HIFU) has been considered as a routine treatment for uterine fibroids and adenomyosis in China. Contrast-enhanced ultrasound (CEUS) has been proposed as another option to assess the treatment efficacy during HIFU treatment. The aim of this investigation is to evaluate the adverse effects of HIFU ablation for benign uterine diseases in a group of patients studied with ultrasound contrast agent (UCA), in comparison with a group of patients not exposed to UCA. From November 2010 to December 2013, 2604 patients with benign uterine diseases were treated with HIFU. Among them, 1300 patients were exposed to an UCA, whereas 1304 patients were not.During HIFU procedure, the incidences of leg pain, sacral/buttock pain, groin pain, treatment area pain, and the discomfort "hot" sensation on skin were higher in the patients who were exposed to SonoVue (Bracco, Milan, Italy) than those who were not (20.5% vs 11.7%, 52.5% vs 42.3%, 6.5% vs 4.5%, 68.9% vs 55.4%, and 48.1% vs 42.9%, respectively). Among the postoperative adverse effects, the incidence of lower abdominal pain was significantly higher in patients who were exposed to an UCA than those who were not (51.2% vs 39.9%, P < 0.05). Two patients who were exposed to an UCA had acute renal function failure.In conclusion, UCA may increase the incidences of some common HIFU-related adverse effects during HIFU treatment for benign uterine diseases, but most of which were acceptable and self-limited. After HIFU treatment, renal function should be monitored in patients with a history of hypertension or taking nonsteroidal anti-inflammatory drugs.

Intraprocedure contrast enhanced ultrasound: the value in assessing the effect of ultrasound-guided high intensity focused ultrasound ablation for uterine fibroids

PURPOSE

To investigate the value of microbubble contrast-enhanced ultrasound (CEUS) in evaluating the treatment response of uterine fibroids to HIFU ablation.

MATERIALS AND METHODS

Sixty-eight patients with a solitary uterine fibroid from the First Affiliated Hospital of Chongqing Medical University were included and analyzed. All patients underwent pre- and post-treatment magnetic resonance imaging (MRI) with a standardized protocol, as well as pre-evaluation, intraprocedure, and immediate post-treatment CEUS. CEUS and MRI were compared by different radiologists.

RESULTS

In comparison with MRI, CEUS showed that the size of fibroids, volume of fibroids, size of non-perfused regions, non-perfused volume (NPV) or fractional ablation (NPV ratio) was similar to that of MRI. In terms of CEUS examination results, the median volume of fibroids was 75.2 (interquartile range, 34.2-127.3) cm(3), the median non-perfused volume was 54.9 (interquartile range, 28.0-98.1) cm(3), the mean fractional ablation was 83.7±13.6 (range, 30.0-100.0)%. In terms of MRI examination results, the median volume of fibroids was 74.1 (interquartile range, 33.4-116.2) cm(3). On the basis of contrast-enhanced T1-weighted images immediately after HIFU treatment, the median non-perfused volume was 58.5 (interquartile range, 27.7-100.0) cm(3), the average fractional ablation was 84.2±14.2 (range, 40.0-100.0)%.

CONCLUSIONS

CEUS clearly showed the size of fibroids and the non-perfused areas of the fibroid. Results from CEUS correlated well with results obtained from MRI.