High intensity focused ultrasound: surgery of the future?

Comprehensive Evaluation of the BeShape One Device: Assessing Thermal Safety in Noninvasive Body Contouring Using Advanced Techniques

OBJECTIVES

This study aims to assess the thermal safety profile of the BeShape One Device, a noninvasive, high-intensity, non-focused ultrasound device designed for reducing waist circumference. This device possesses several features that distinguish it from other commercial ultrasound-based fat reduction devices. The study focuses on evaluating temperature-related physiological changes through thermal safety analysis and histopathology in a swine model.

MATERIALS AND METHODS

The study utilized three types of applicators-active, demo, and modified-to comprehensively assess the device's impact on various skin layers. Five female Large White X Landrace swine were involved in the study, and the BeShape One Device was applied to designated treatment sites using a specific treatment protocol. The assessment included clinical observations, skin reaction evaluations, gross pathology, histopathological analyses, and advanced temperature measurement techniques, including needle thermocouples, thermal cameras, COMSOL modeling, and CEM43 analysis.

RESULTS

Clinical observations indicated the animals' overall well-being throughout the study. Skin reactions, including erythema, edema, bruising, and crust formation, were temporary and resolved over time. Gross pathology revealed no treatment-related pathologies, except for a discoloration related to a tattoo procedure. Histopathological analyses at 30 and 90 days posttreatment demonstrated an absence of heat-related lesions in skin layers. Needle thermocouples and thermal camera measurements supported the device's ability to maintain consistent thermal homogeneity. COMSOL modeling and CEM43 analysis predicted no thermal damage to the skin, confirming the safety of the BeShape One Device.

CONCLUSIONS

Under the experimental conditions, the BeShape One Device demonstrated a favorable safety profile. Clinically and histopathologically, no adverse effects were observed. The device's ability to achieve thermal homogeneity in skin layers was validated through advanced temperature measurement techniques. COMSOL modeling and CEM43 analysis further supported the conclusion that the device is safe, making it a promising option for noninvasive body contouring procedures.

Management of the Devastated Bladder Outlet after Prostate CANCER Treatment

PURPOSE OF REVIEW

Devastating complications of the bladder outlet resulting from prostate cancer treatments are relatively uncommon. However, the combination of the high incidence of prostate cancer and patient longevity after treatment have raised awareness of adverse outcomes deteriorating patients' quality of life. This narrative review discusses the diagnostic work-up and management options for bladder outlet obstruction resulting from prostate cancer treatments, including those that require urinary diversion.

RECENT FINDINGS

The devastated bladder outlet can be a consequence of the treatment of benign conditions, but more frequently from complications of pelvic cancer treatments. Regardless of etiology, the initial treatment ladder involves endoluminal options such as dilation and direct vision internal urethrotomy, with or without intralesional injection of anti-fibrotic agents. If these conservative strategies fail, surgical reconstruction should be considered. Although surgical reconstruction provides the best prospect of durable success, reconstructive procedures are also associated with serious complications. In the worst circumstances, such as prior radiotherapy, failed reconstruction, devastated bladder outlet with end-stage bladders, or patient's severe comorbidities, reconstruction may neither be realistic nor justified. Urinary diversion with or without cystectomy may be the best option for these patients. Thorough patient counseling before treatment selection is of utmost importance. Outcomes and repercussions on quality of life vary extensively with management options. Meticulous preoperative diagnostic evaluation is paramount in selecting the right treatment strategy for each individual patient. The risk of bladder outlet obstruction, and its severest form, devastated bladder outlet, after treatment of prostate cancer is not negligible, especially following radiation. Management includes endoluminal treatment, open or robot-assisted laparoscopic reconstruction, and urinary diversion in the worst circumstances, with varying success rates.

Complications and adverse events of high-intensity focused ultrasound in its application to gynecological field - a systematic review and meta-analysis

OBJECTIVE

To analyze and summarize the types, incidence rates and relevant influencing factors of adverse events (AEs) after high-intensity focused ultrasound ablation of gynecological diseases and provide reference and basis for handling such events in clinical practice.

METHOD

We searched PubMed, Cochrane Library, Web of Science and Embase databases to retrieve all literature since its establishment until February 2024. We evaluated the quality of included literature and publication bias and conducted a meta-analysis of single group rates for various AEs using Stata 17.0.

RESULTS

This systematic review finally included 41 articles. We summarized 34 kinds of AEs in 7 aspects and conducted a single group rate meta-analysis and sub-group analysis of 16 kinds of AEs. Among the common AEs of High-Intensity Focused Ultrasound (HIFU), the incidence of lower abdominal pain/pelvic pain is 36.1% (95% CI: 24.3%∼48.8%), vaginal bleeding is 20.6% (95% CI: 13.9%∼28.0%), vaginal discharge is 14.0% (95% CI: 9.6%∼19.1%), myoma discharge is 24% (95% CI: 14.6%∼34.8%), buttock pain is 10.8% (95% CI: 6.0%∼16.5%) and sacral pain is 10% (95% CI: 8.8%∼11.2%). Serious complications include uterine rupture, necrotic tissue obstruction requiring surgical intervention, third degree skin burns and persistent lower limb pain or movement disorders.

CONCLUSION

The common AEs after HIFU surgery are mostly mild and controllable, and the incidence of serious complications is extremely low. By reasonable prevention and active intervention, these events can be further reduced, making it a safe and effective treatment method. It is a good choice for patients who crave noninvasive treatment or have other surgical contraindications.

Focused Ultrasound-Responsive Nanocomposite with Near-Infrared II Mechanoluminescence for Spatiotemporally Selective Immune Activation in Lymph Nodes

The immune regulation of the lymphatic system, especially the lymph node (LN), is of great significance for the treatment of diseases and the inhibition of pathogenic organisms spreading in the body. However, achieving precise spatiotemporal control of immune cell activation in LN in vivo remains a challenge due to tissue depth and off-target effects. Furthermore, minimally invasive and real-time feedback methods to monitor the regulation of the immune system in LN are lacking. Here, focused ultrasound responsive immunomodulator loaded nanoplatform (FURIN) with near-infrared II (NIR-II) luminescence is designed to achieve spatiotemporally controllable immune activation in LN in vivo. The NIR-II persistent luminescence of FURIN can track its delivery in LN through bioimaging. Under focused ultrasound (FUS) stimulation, the immunomodulator encapsulated in FURIN can be released locally in the LN to activate immune cells such as dendritic cells and the NIR-II mechanoluminescence of FURIN provides real-time optical feedback signals for immune activation. This work points to a FUS mediated, spatiotemporal selective immune activation strategy in vivo with the feedback control of luminescence signals via ultrasound responsive nanocomposite, which is of great significance in improving the efficacy and reducing the side effect of immune regulation for the development of potential immunotherapeutic methods in the future.

The Effectiveness of High-Intensity Focused Ultrasound in Treating Nasal Obstruction Caused by Inferior Turbinate Hypertrophy: A Clinical Study

Background Nasal obstruction due to inferior turbinate hypertrophy is a common medical complaint among ENT clinic patients, which can significantly affect the patient's quality of life, and some are compelled to use topical intranasal decongestants. Conservative management is the first line of treatment; however, surgical reduction of the inferior turbinate becomes necessary if the symptoms persist after three months of treatment. The optimal surgical technique is controversial. High-intensity focused ultrasound (HIFU) is a minimally invasive surgical option that targets tissue volume precisely and minimally impacts surrounding tissue. This study aimed to assess the effectiveness and safety of HIFU in treating patients suffering from nasal obstruction due to inferior turbinate hypertrophy. Methods This prospective study was conducted from February to December 2016. The study lasted over six months. Patients with a history of allergic and non-allergic rhinitis participated in this study. It included 43 patients who had been experiencing chronic nasal obstruction due to bilateral inferior turbinate hypertrophy and had not shown improvement after three months of medical treatment. The patients underwent Ultrasound Volumetric Tissue Reduction (UVTR) surgery using the D & A Ultrasurg device (Diamant Medical Equipment Ltd., Amman, Jordan) under local anesthesia. The effectiveness, safety, and tolerance of HIFU were assessed subjectively for six months using a well-designed questionnaire utilizing a visual analog scale (VAS) and nasal endoscopy after the surgery. Results The study included 43 patients, 22 male and 21 female, aged 13 to 65 years. The study found that 40 (93%) patients showed significant improvement in nasal obstruction within a month of the surgery. However, three (7%) patients continued to experience persistent nasal obstruction even after six months of follow-up. The procedure was well-tolerated, with low rates of complications after surgery and reasonable pain control. During the surgery, 20 (46.5%) patients reported mild pain described as a pressure-like sensation, and 10 out of 43 patients (23%) required paracetamol after the procedure. Four patients (9.3%) had mild bleeding, which was treated with an ultrasound nasal probe without nasal packing. All patients experienced crusting of the nasal cavity during the first week, but no crustation was observed after the first month. There were no reported cases of synechia among the patients. Conclusion This study confirms that HIFU treatment is a reliable and effective treatment for improving short-term nasal obstruction caused by inferior turbinate hypertrophy. The procedure is easily applied and well-tolerated in outpatient clinics.

Current state of the art of traditional and minimal invasive epilepsy surgery approaches

Introduction

Open resective surgery remains the main treatment modality for refractory epilepsy, but is often considered a last resort option due to its invasiveness.

Research question

This manuscript aims to provide an overview on traditional as well as minimally invasive surgical approaches in modern state of the art epilepsy surgery.

Materials and methods

This narrative review addresses both historical and contemporary as well as minimal invasive surgical approaches in epilepsy surgery. Peer-reviewed published articles were retrieved from PubMed and Scopus. Only articles written in English were considered for this work. A range of traditional and minimally invasive surgical approaches in epilepsy surgery were examined, and their respective advantages and disadvantages have been summarized.

Results

The following approaches and techniques are discussed: minimally invasive diagnostics in epilepsy surgery, anterior temporal lobectomy, functional temporal lobectomy, selective amygdalohippocampectomy through a transsylvian, transcortical, or subtemporal approach, insulo-opercular corticectomies compared to laser interstitial thermal therapy, radiofrequency thermocoagulation, stereotactic radiosurgery, neuromodulation, high intensity focused ultrasound, and disconnection surgery including callosotomy, hemispherotomy, and subpial transections.

Discussion and conclusion

Understanding the benefits and disadvantages of different surgical approaches and strategies in traditional and minimal invasive epilepsy surgery might improve the surgical decision tree, as not all procedures are appropriate for all patients.

US-guided high-intensity focused ultrasound in pancreatic cancer treatment: a consensus initiative between Chinese and European HIFU centers

Purpose: Ultrasound-guided high-intensity focused ultrasound (USgHIFU) represents a safe and effective non-invasive thermoablative technique for managing inoperable pancreatic cancer. This treatment method significantly alleviates disease-related symptoms and reduces pancreatic tumor volume. However, the current body of evidence is constrained by a lack of randomized controlled trials. The utilization of USgHIFU is primarily indicated for patients with unresectable, locally advanced, or metastatic pancreatic cancer, particularly those experiencing symptoms due to a locally advanced primary tumor.Methods: This collaborative consensus paper, involving European and Chinese HIFU centers treating pancreatic cancer, delineates criteria for patient selection, focusing on those most likely to benefit from USgHIFU treatment. Consideration is given to endpoints encompassing symptom alleviation, local response rates, other oncological outcomes, as well as overall and progression-free survival. Additionally, this paper defines relevant contraindications, side effects, and complications associated with USgHIFU. The publication also explores the feasibility and role of USgHIFU within the context of palliative care, including standard systemic chemotherapy.Results: The non-invasive local treatment of advanced pancreatic cancer using HIFU should be regarded as an adjunctive option alongside systemic chemotherapy or best supportive care for managing this aggressive disease. Based on the ability of USgHIFU therapy to mitigate pain and reduce primary tumor volume, it should be considered as a complementary therapy for symptomatic patients with inoperable pancreatic cancer and as a potential means of tumor debulking. The underutilized yet promising USgHIFU exhibits the potential to enhance patients' quality of life by alleviating cancer-related pain. Experts in the field should evaluate this treatment option be evaluated by experts in this field, with this consensus paper potentially serving as a guiding resource for the medical community.Conclusions: US-guided HIFU for advanced pancreatic cancer addresses treatment goals, available options, success rates, and limitations. As a non-invasive, effective local therapy, complementary to chemotherapy and best supportive care, it plays a pivotal role in pain relief, reducing of tumor volume, and potentially improving survival rates.

Magnetoelectric Nanodiscs Enable Wireless Transgene-Free Neuromodulation

Deep-brain stimulation (DBS) with implanted electrodes revolutionized treatment of movement disorders and empowered neuroscience studies. Identifying less invasive alternatives to DBS may further extend its clinical and research applications. Nanomaterial-mediated transduction of magnetic fields into electric potentials offers an alternative to invasive DBS. Here, we synthesize magnetoelectric nanodiscs (MENDs) with a core-double shell Fe3O4-CoFe2O4-BaTiO3 architecture with efficient magnetoelectric coupling. We find robust responses to magnetic field stimulation in neurons decorated with MENDs at a density of 1 μg/mm2 despite individual-particle potentials below the neuronal excitation threshold. We propose a model for repetitive subthreshold depolarization, which combined with cable theory, corroborates our findings in vitro and informs magnetoelectric stimulation in vivo. MENDs injected into the ventral tegmental area of genetically intact mice at concentrations of 1 mg/mL enable remote control of reward behavior, setting the stage for mechanistic optimization of magnetoelectric neuromodulation and inspiring its future applications in fundamental and translational neuroscience.

High-Intensity Focused Ultrasound (Sonablate®) for Prostate Cancer: Preliminary Outcomes in Taiwan

PURPOSE

We reported preliminary outcomes of high-intensity focused ultrasound (HIFU) [Sonablate®] in the combination of transurethral resection of the prostate for localized prostate cancer in Taiwan.

METHODS

Seventy-seven patients using Sonablate® HIFU for localized prostate cancer were enrolled in this study from April 2021 to December 2022. Prostate-specific antigen biochemical recurrence, International Index of Erectile Function (IIEF)-5 scores, International Prostate Symptom Score (IPSS), quality of life (QoL) scores, and postoperative complications were recorded during follow-up.

RESULTS

Overall, 19.5% of patients were low-risk, 36.4% were intermediate-risk, and 44.1% were high-risk according to the D'Amico risk classification. The median follow-up was 12.09 ± 5.85 months, and the biochemical-free survival rates for the low-, intermediate-, and high-risk groups were 100% (15/15), 96.4% (27/28), and 79.4% (27/34), respectively. Four patients (5.2%) received salvage radiotherapy and all maintained biochemical-free survival. The mean IPSS and QoL scores before versus after HIFU were 10.4 versus 6.8 (p = 0.003) and 3.2 versus 3.0 (p = 0.096), respectively. There was no statistically significant change in preoperative and postoperative IIEF scores (20.6 vs. 19; p = 0.062) in patients who had an IIEF score of >15 at baseline and received nerve-sparing procedures (subtotal ablation).

CONCLUSIONS

The results of Sonablate® HIFU in Taiwan indicated adequate short-term cancer control, excellent potency, and continence preservation. HIFU can achieve improvement of IPSS with low complication rates.

Tumor phantom model for MRI-guided focused ultrasound ablation studies

BACKGROUND

The persistent development of focused ultrasound (FUS) thermal therapy in the context of oncology creates the need for tissue-mimicking tumor phantom models for early-stage experimentation and evaluation of relevant systems and protocols.

PURPOSE

This study presents the development and evaluation of a tumor-bearing tissue phantom model for testing magnetic resonance imaging (MRI)-guided FUS (MRgFUS) ablation protocols and equipment based on MR thermometry.

METHODS

Normal tissue was mimicked by a pure agar gel, while the tumor simulator was differentiated from the surrounding material by including silicon dioxide. The phantom was characterized in terms of acoustic, thermal, and MRI properties. US, MRI, and computed tomography (CT) images of the phantom were acquired to assess the contrast between the two compartments. The phantom's response to thermal heating was investigated by performing high power sonications with a 2.4 MHz single element spherically focused ultrasonic transducer in a 3T MRI scanner.

RESULTS

The estimated phantom properties fall within the range of literature-reported values of soft tissues. The inclusion of silicon dioxide in the tumor material offered excellent tumor visualization in US, MRI, and CT. MR thermometry revealed temperature elevations in the phantom to ablation levels and clear evidence of larger heat accumulation within the tumor owing to the inclusion of silicon dioxide.

CONCLUSION

Overall, the study findings suggest that the proposed tumor phantom model constitutes a simple and inexpensive tool for preclinical MRgFUS ablation studies, and potentially other image-guided thermal ablation applications upon minimal modifications.

Artificial intelligence-assisted ultrasound-guided focused ultrasound therapy: a feasibility study

OBJECTIVES

Focused ultrasound (FUS) therapy has emerged as a promising noninvasive solution for tumor ablation. Accurate monitoring and guidance of ultrasound energy is crucial for effective FUS treatment. Although ultrasound (US) imaging is a well-suited modality for FUS monitoring, US-guided FUS (USgFUS) faces challenges in achieving precise monitoring, leading to unpredictable ablation shapes and a lack of quantitative monitoring. The demand for precise FUS monitoring heightens when complete tumor ablation involves controlling multiple sonication procedures.

METHODS

To address these challenges, we propose an artificial intelligence (AI)-assisted USgFUS framework, incorporating an AI segmentation model with B-mode ultrasound imaging. This method labels the ablated regions distinguished by the hyperechogenicity effect, potentially bolstering FUS guidance. We evaluated our proposed method using the Swin-Unet AI architecture, conducting experiments with a USgFUS setup on chicken breast tissue.

RESULTS

Our results showed a 93% accuracy in identifying ablated areas marked by the hyperechogenicity effect in B-mode imaging.

CONCLUSION

Our findings suggest that AI-assisted ultrasound monitoring can significantly improve the precision and control of FUS treatments, suggesting a crucial advancement toward the development of more effective FUS treatment strategies.

High-Intensity Focused Ultrasound Increases Collagen and Elastin Fiber Synthesis by Modulating Caveolin-1 in Aging Skin

Caveolin-1 (Cav-1) induces cellular senescence by reducing extracellular signal-regulated kinase (ERK)1/2 phosphorylation and activating p53 via inhibition of mouse double minute 2 homolog (MDM2) and sirtuin 1 (Sirt1), promoting cell cycle arrest and decreasing fibroblast proliferation and collagen synthesis. High-intensity focused ultrasound (HIFU) treatment increases collagen synthesis, rejuvenating skin. Using H2O2-induced senescent fibroblasts and the skin of 12-month-old mice, we tested the hypothesis that HIFU increases collagen production through Cav-1 modulation. HIFU was administered at 0.3, 0.5, or 0.7 J in the LINEAR and DOT modes. In both models, HIFU administration decreased Cav-1 levels, increased ERK1/2 phosphorylation, and decreased the binding of Cav-1 with both MDM2 and Sirt1. HIFU administration decreased p53 activation (acetylated p53) and p21 levels and increased cyclin D1, cyclin-dependent kinase 2, and proliferating cell nuclear antigen levels in both models. HIFU treatment increased collagen and elastin expression, collagen fiber accumulation, and elastin fiber density in aging skin, with 0.5 J in LINEAR mode resulting in the most prominent effects. HIFU treatment increased collagen synthesis to levels similar to those in Cav-1-silenced senescent fibroblasts. Our results suggest that HIFU administration increases dermal collagen and elastin fibers in aging skin via Cav-1 modulation and reduced p53 activity.

Successful treatment of submental fat using a non-focused pulsed ultrasound

BACKGROUND

The prevalence of non-invasive aesthetic treatments is increasing, with patients demanding easier, safer, and more effective non-invasive cosmetic procedures. Submental fat is usually addressed using liposuction, which is associated with significant adverse events and a long recovery. Although newer, non-invasive submental fat treatments are gaining popularity, they are often complex, require frequent injections, or have adverse side effects.

AIMS

Assess the safety and efficacy of vacuum-assisted acoustic wave technology for treating submental.

PATIENTS/METHODS

Fourteen female patients underwent a total of three weekly 15-min treatments using ultrasound with a 40 mm bell-shaped sonotrode. Improvement in submental fat was assessed 3 months after the final treatment using questionnaires for the patients and physicians. Two blinded dermatologists rated each patient using the Clinician-Reported Submental Fat Rating Scale (CR-SMFRS) 5-point scale.

RESULTS

Both physicians rated a significant improvement in all 14 patients. Furthermore, self-evaluation of the 14 patients on a 1 to 5 satisfaction scale averaged 2.14, indicating that most patients were somewhat satisfied.

CONCLUSION

This study demonstrates that a three-treatment course with an acoustic wave ultrasound applicator with 1-week intervals leads to a significant reduction in submental fat and can be used as a novel, efficient treatment paradigm.

The Role of Ultrasound in Cancer and Cancer-Related Pain-A Bibliometric Analysis and Future Perspectives

Ultrasound has a deep penetrating ability with minimal or no tissue injury, while cancer-mediated complications during diagnosis, therapy, and surgery have become a serious challenge for clinicians and lead to the severity of the primary condition (cancer). The current study highlights the importance of ultrasound imaging and focused ultrasound therapy during cancer diagnosis, pain reduction, guidance for surgical resection of cancer, and the effectiveness of chemotherapy. We performed the bibliometric analysis on research domains involving ultrasound, cancer management, pain, and other challenges (chemotherapy, surgical guidance, and postoperative care), to observe the trend by which the research field has grown over the years and propose a possible future trend. The data was obtained from the Web of Science, processed, and exported as plain text files for analysis in the Bibliometrix R web interface using the Biblioshiny package. A total of 3248 documents were identified from 1100 journal sources. A total of 390 articles were published in 2022, with almost a 100% growth rate from previous years. Based on the various network analysis, we conclude that the outcome of the constant research in this domain will result in better patient care during the management of various diseases, including cancer and other co-morbidities.

Treatment of mammary cancer with focused ultrasound: A pilot study in canine and feline patients

In recent years, veterinary medicine has expanded its practices beyond conventional methods, gradually integrating the Focused Ultrasound (FUS) technology in the care of companion animals like dogs and cats. The current study aimed to examine the feasibility and provide insights into the application of thermal FUS in canine and feline mammary cancer therapy. FUS was delivered by a 2-MHz single-element spherically focused ultrasonic transducer as integrated with an existing robotic positioning device. The functionality of the FUS system and sonication protocol in efficiently and safely ablating live tissue was initially validated in a rabbit thigh model in a laboratory environment. Nine (9) dogs and cats with superficial mammary cancer were recruited through a dedicated campaign according to specific safety criteria. The veterinary patients underwent FUS ablation followed by immediate surgical resection of the entire malignancy. Histopathology examination demonstrated well-defined regions of coagulative necrosis in all treated tumors with no off-target damage. Further study with a larger patient population is needed to confirm the current findings and demonstrate the safety and feasibility of complete FUS ablation of deep-seated tumors.

Weakly nonlinear focused ultrasound in viscoelastic media containing multiple bubbles

To facilitate practical medical applications such as cancer treatment utilizing focused ultrasound and bubbles, a mathematical model that can describe the soft viscoelasticity of human body, the nonlinear propagation of focused ultrasound, and the nonlinear oscillations of multiple bubbles is theoretically derived and numerically solved. The Zener viscoelastic model and Keller-Miksis bubble equation, which have been used for analyses of single or few bubbles in viscoelastic liquid, are used to model the liquid containing multiple bubbles. From the theoretical analysis based on the perturbation expansion with the multiple-scales method, the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation, which has been used as a mathematical model of weakly nonlinear propagation in single phase liquid, is extended to viscoelastic liquid containing multiple bubbles. The results show that liquid elasticity decreases the magnitudes of the nonlinearity, dissipation, and dispersion of ultrasound and increases the phase velocity of the ultrasound and linear natural frequency of the bubble oscillation. From the numerical calculation of resultant KZK equation, the spatial distribution of the liquid pressure fluctuation for the focused ultrasound is obtained for cases in which the liquid is water or liver tissue. In addition, frequency analysis is carried out using the fast Fourier transform, and the generation of higher harmonic components is compared for water and liver tissue. The elasticity suppresses the generation of higher harmonic components and promotes the remnant of the fundamental frequency components. This indicates that the elasticity of liquid suppresses shock wave formation in practical applications.

Development of an US, MRI, and CT imaging compatible realistic mouse phantom for thermal ablation and focused ultrasound evaluation

Tissue mimicking phantoms (TMPs) play an essential role in modern biomedical research as cost-effective quality assurance and training tools, simultaneously contributing to the reduction of animal use. Herein, we present the development and evaluation of an anatomically accurate mouse phantom intended for image-guided thermal ablation and Focused Ultrasound (FUS) applications. The proposed mouse model consists of skeletal and soft tissue mimics, whose design was based on the Computed tomography (CT) scans data of a live mouse. Advantageously, it is compatible with US, CT, and Magnetic Resonance Imaging (MRI). The compatibility assessment was focused on the radiological behavior of the phantom due to the lack of relevant literature. The X-ray linear attenuation coefficient of candidate materials was estimated to assess the one that matches best the radiological behavior of living tissues. The bone part was manufactured by Fused Deposition Modeling (FDM) printing using Acrylonitrile styrene acrylate (ASA) material. For the soft-tissue mimic, a special mold was 3D printed having a cavity with the unique shape of the mouse body and filled with an agar-based silica-doped gel. The mouse phantom accurately matched the size and reproduced the body surface of the imaged mouse. Tissue-equivalency in terms of X-ray attenuation was demonstrated for the agar-based soft-tissue mimic. The phantom demonstrated excellent MRI visibility of the skeletal and soft-tissue mimics. Good radiological contrast between the skeletal and soft-tissue models was also observed in the CT scans. The model was also able to reproduce realistic behavior during trans-skull sonication as proved by thermocouple measurements. Overall, the proposed phantom is inexpensive, ergonomic, and realistic. It could constitute a powerful tool for image-guided thermal ablation and FUS studies in terms of testing and optimizing the performance of relevant equipment and protocols. It also possess great potential for use in transcranial FUS applications, including the emerging topic of FUS-mediated blood brain barrier (BBB) disruption.

Modeling for Quantitative Analysis of Nakagami Imaging in Accurate Detection and Monitoring of Therapeutic Lesions by High-Intensity Focused Ultrasound

OBJECTIVE

Nakagami imaging is an appealing monitoring and evaluation technique for high-intensity focused ultrasound treatment when bubbles are present in ultrasound images. This study aimed to investigate the accuracy of thermal lesion detection using Nakagami imaging.

METHODS

Simulations were conducted to explore and quantify the influence of the bubbles and the subresolvable effect at the boundary of the thermal lesion on thermal lesion detection. The thermal ablation experiments were conducted in phantom and porcine liver ex vivo.

RESULTS

In the simulation, the estimated lateral and axial size of the thermal lesion in the Nakagami image was 4.91 and 4.79 mm, close to the actual size (5 × 5 mm). The simulation results indicated that the subresolvable region in high-intensity focused ultrasound treatment thermal ablation mainly happened at the boundary between bubbles and the untreated region and does not affect the accuracy of thermal lesion detection. The accurate detection of the thermal lesion using Nakagami imaging mainly depends on bubbles and thermal lesion characterization. Our thermal ablation experiments confirmed that Nakagami imaging has the ability to accurately identify thermal lesions from bubbles.

CONCLUSION

The subresolvable effect is helpful for thermal lesion identification, and precision is related to the Nakagami values chosen for boundary division in Nakagami imaging. Therefore, Nakagami imaging is a promising method for accurately evaluating thermal lesions. Further studies in vivo and in clinical settings will be needed to explore its potential applications.

Mid-term efficacy grading evaluation and predictive factors of magnetic resonance-guided focused ultrasound surgery for painful bone metastases: a multi-center study

OBJECTIVES

MR imaging-guided focused ultrasound surgery (MRgFUS) is an emerging non-invasive treatment. It is helpful in investigating the mid-term grading efficacy and safety of MRgFUS, and possible risk factors in participants with painful bone metastases.

METHODS

This four-center prospective study enrolled 96 participants between June 2016 and May 2019 with painful bone metastases. The Numerical Rating Scale (NRS), Brief Pain Inventory-Quality of Life (BPI-QoL) score, morphine equivalent daily dose (MEDD), and the adverse events (AEs) were recorded before and at 1 week, 1 month, 2 months, and 3 months after MRgFUS. The repeated ANOVA tests were used to analyze the change in NRS and BPI-QoL, and logistic regression analysis was used to analyze the possible risk factors.

RESULTS

A total of 82 participants completed the 3-month follow-up period. And 16 (19.5%) participants were complete responders (CR), 46 (56.1%) participants were effective responders (ER), and the other 20 (24.4%) participants were non-responders (NR). The NRS (2.67 ± 2.47 at 3 months compared to 6.38 ± 1.70 before treatment) and BPI-QoL score (3.11 ± 2.51 at 3 months compared to 5.40 ± 1.85 before treatment) significantly decreased after the treatment at all time points (p < 0.001). Eleven adverse events were recorded and they were all cured within 1 to 52 days after treatment. The non-perfused volume (NPV) ratio (p = 0.001) and the bone metastases lesion type (p = 0.025) were the key risk factors.

CONCLUSIONS

MRgFUS can be used as a non-invasive, effective, and safe modality to treat painful bone metastases. NPV ratio and the lesion type may be used as affecting factors to predict the mid-term efficacy of MRgFUS.

KEY POINTS

• MRgFUS can be considered a non-invasive, effective, and safe modality to treat painful bone metastases. • The NRS and BPI-QoL score at 1 week, 1 month, 2 months, and 3 months all decreased significantly (p < 0.001) after receiving MRgFUS. Among 82 participants, 16 (19.5%) were complete responders, 46 (56.1%) were effective responders, and the other 20 (24.4%) were non-responders. • According to logistic regression analysis, non-perfused volume ratio and the bone metastases lesion type were the affecting factors to predict the mid-term efficacy of MRgFUS. The adjusted OR of non-perfused volume ratio was 0.86 (p = 0.001), and osteoblastic lesion type was 0.06 (p = 0.025).

A Systematic Review of the Efficacy of Microfocused Ultrasound for Facial Skin Tightening

Objective: to systematically review the efficacy of microfocused ultrasound (MFU) for facial skin tightening. Methods: A systematic search was performed (Pubmed, Embase) to assess the efficacy of single MFU treatments for facial skin tightening. Eligible studies included randomised controlled trials, controlled trials, cohort studies and case series (n ≥ 10). Objective and subjective outcomes were assessed. Results: A total of 693 studies were identified of which 16 studies were eligible. All the studies involved female patients. MFU is capable of tightening the skin, as observed in studies measuring the results of brow lifts (0.47−1.7 mm) and submental lifts (measured as a 26−45 mm2 reduction in the submental area on lateral photographs). Data from the Global Aesthetic Improvement Scale (GAIS) were pooled, and the day 90 pooled subjective investigator reported scores (IGAIS) (n = 337) showed that 92% of the patients demonstrated an improvement in skin tightening and/or in wrinkle reduction which continued up to one year. Longer-term follow-up data are not available. The patient-reported pooled scores (SGAIS) (n = 81) showed that the skin improvements were mild and continued to increase from 42% (90 days) to 53% (360 days) post-treatment. The MFU treatment was moderately painful and caused transient erythema with or without oedema. Other adverse effects were rare (2%), including dysesthesia (numbness or hypersensitivity), bruising and stinging, mandibular burns, striations and contact dermatitis. Various device settings, treatment protocols and energies were applied. Excessive skin laxity and a BMI > 30 were posed as relative contraindications for MFU treatment because positive results declined with an increase in laxity and BMI. Conclusions: MFU treatment is effective in tightening female patients’ mildly to moderately lax facial skin. Future studies should focus on objective treatment outcomes, optimising treatment regimens and male patients.

Analysis of the results of high-intensity focused ultrasound for patients with advanced pancreatic cancer

OBJECTIVE

To investigate the safety, local ablation efficacy, analgesic effects, and factors influencing the survival of patients with advanced pancreatic cancer treated with high-intensity focused ultrasound (HIFU).

MATERIALS AND METHODS

Patients with advanced pancreatic cancer who underwent HIFU for the first time at the Suining Central Hospital between January 2018 and September 2022 were enrolled. The efficacy of tumor ablation was assessed using enhanced computed tomography (CT) and magnetic resonance imaging (MRI), pain relief was assessed using the visual analog scale (VAS), and complications and survival rates were investigated. The Kaplan-Meier method and a Cox regression model were used to analyze the independent risk factors that may have affected prognosis.

RESULTS

Intraoperative ultrasonography showed varying degrees of grayscale changes in all cases. One month after surgery, enhanced computed tomography or magnetic resonance imaging examinations showed complete or partial responses in 85.22% of the patients. Pain relief was achieved in 98.21% of the patients. No postoperative complications of SIR-C grade or higher were observed. The overall median survival time (MST) was 12.1 months. Cox multifactorial analysis showed that the main factors affecting overall survival (OS) were clinical stage, preoperative liver function, and combination chemotherapy.

CONCLUSION

HIFU is safe and effective for pancreatic cancer treatment, and has the potential to become an important supplement for the treatment of advanced pancreatic cancer. This approach needs to be further verified by multi-center and large-sample studies.

Experiments and simulations demonstrating the rapid ultrasonic rewarming of frozen tissue cryovials

The development of methods to safely rewarm large cryopreserved biological samples remains a barrier to the widespread adoption of cryopreservation. Here, experiments and simulations were performed to demonstrate that ultrasound can increase rewarming rates relative to thermal conduction alone. An ultrasonic rewarming setup based on a custom 444 kHz tubular piezoelectric transducer was designed, characterized, and tested with 2 ml cryovials filled with frozen ground beef. Rewarming rates were characterized in the -20 °C to 5 °C range. Thermal conduction-based rewarming was compared to thermal conduction plus ultrasonic rewarming, demonstrating a tenfold increase in rewarming rate when ultrasound was applied. The maximum recorded rewarming rate with ultrasound was 57° C/min, approximately 2.5 times faster than with thermal conduction alone. Coupled acoustic and thermal simulations were developed and showed good agreement with the heating rates demonstrated experimentally and were also used to demonstrate spatial heating distributions with small (<3° C) temperature differentials throughout the sample when the sample was below 0° C. The experiments and simulations demonstrate the potential for ultrasonic cryovial rewarming with a possible application to large volume rewarming, as faster rewarming rates may improve the viability of cryopreserved tissues and reduce the time needed for cells to regain normal function.

Salvage high intensity focused ultrasound for residual or recurrent cervical cancer after definitive chemoradiotherapy

Objective

The treatment of residual/recurrent cervical cancer within a previously irradiated area is challenging and generally associated with a poor outcome. Local treatments such as salvage surgery and re-irradiation are usually traumatic and have limited efficacy. High intensity focused ultrasound (HIFU) treatment can directly ablate solid tumors without damaging neighboring healthy tissue. However, the HIFU studies for these patients are limited. Experience gained over the course of 10 years with the use of HIFU for the management of residual/recurrent cervical cancer after chemoradiotherapy is reported herein.

Methods

153 patients with residual/recurrent cervical cancer in a previously irradiated field who received HIFU treatment between 2010 and 2021 were retrospectively analyzed. Adverse effects, survival benefit and factors affecting prognosis were given particular attention.

Results

A total of 36 patients (23.5%) achieved a partial response following HIFU treatment and 107 patients (69.9%) had stable disease. The objective response and disease control rates were 23.5% and 93.5%, respectively. The median progression-free survival (mPFS) and median overall survival (mOS) were 17.0 months and 24.5 months, respectively. Moreover, patients with lesions ≥1.40 cm before HIFU treatment and a shrinkage rate ≥ 30% after treatment had a higher mPFS and mOS, and patients with lesions ≤1.00 cm after HIFU treatment had a higher mPFS (P=<0.05). All the treatment-related adverse events were limited to minor complications, which included skin burns, abdominal pain and vaginal discharge.

Conclusions

HIFU treatment is likely a preferred option for cervical cancer patients with residual disease or recurrence following CRT that can safely improve the local control rate and extend survival.

3D-printed microrobots from design to translation

Microrobots have attracted the attention of scientists owing to their unique features to accomplish tasks in hard-to-reach sites in the human body. Microrobots can be precisely actuated and maneuvered individually or in a swarm for cargo delivery, sampling, surgery, and imaging applications. In addition, microrobots have found applications in the environmental sector (e.g., water treatment). Besides, recent advancements of three-dimensional (3D) printers have enabled the high-resolution fabrication of microrobots with a faster design-production turnaround time for users with limited micromanufacturing skills. Here, the latest end applications of 3D printed microrobots are reviewed (ranging from environmental to biomedical applications) along with a brief discussion over the feasible actuation methods (e.g., on- and off-board), and practical 3D printing technologies for microrobot fabrication. In addition, as a future perspective, we discussed the potential advantages of integration of microrobots with smart materials, and conceivable benefits of implementation of artificial intelligence (AI), as well as physical intelligence (PI). Moreover, in order to facilitate bench-to-bedside translation of microrobots, current challenges impeding clinical translation of microrobots are elaborated, including entry obstacles (e.g., immune system attacks) and cumbersome standard test procedures to ensure biocompatibility.

Microbots have attracted attention due to an ability to reach places and perform tasks which are not possible with conventional techniques in a wide range of applications. Here, the authors review the recent work in the field on the fabrication, application and actuation of 3D printed microbots offering a view of the direction of future microbot research.

Persistent Radicals Derived from N-Heterocyclic Carbenes for Material Applications

Persistent radicals are potential building blocks of novel materials in many fields. Recently, highly stable persistent radicals are considered to be within reach, thanks to several radical stabilization strategies such as spin delocalization and steric protection. N-Heterocyclic carbene (NHC)-derived substituents can be attached to a radical center for these purposes, as illustrated by numerous NHC-stabilized radicals reported in the last two decades.This Account describes our recent work on developing NHC-derived persistent radicals, as well as their prospective applications. Considering that NHCs not only stabilize radicals but also reversibly interact with gas molecules, in 2015 our group reported NHC-nitric oxide (NHC-NO) radicals produced by reversibly trapping nitric oxide (NO) radical gas in NHCs. The resultant compounds were loaded into biocompatible poly(ethylene glycol)-block-poly(caprolactone) (PEG-b-PCL) micelles and injected into tumor-bearing mice. Then, NO release was triggered by high-intensity focused ultrasound irradiation of the tumor tissue. Furthermore, the NHC-NO radicals could also serve as a platform to generate other organic radicals such as oxime ether or iminyl radicals. Apart from medicine-related applications, radicals stabilized by NHCs can be used as energy storage materials. In this context, the triazenyl radical containing two NHC units reported by our laboratory could be a cathode active material in batteries, as an organic alternative to LiCoO₂. The subsequently prepared unsymmetrical triazenyl radical derivatives were applied as anolytes in nonaqueous all-organic redox flow batteries. In addition, a ferrocene-based redox flow battery anolyte was obtained by introducing NHC-derived substituents that effectively stabilize the ferrocenate derivatives previously reported only at low temperatures. The batteries containing NHC-supported radicals exhibited high energy efficiency and insignificant radical decomposition over multiple cycles. Finally, toward developing air-persistent organic radicals for flexible devices and MRI contrasting agents, we also highlight our recent air- and physiologically stable organic radicals derived from NHCs. Coordination of tris(pentafluorophenyl)borane to the NHC-NO radical produced a new radical cation that is stable in an organic solvent under air for several months. The readily accessible 1,2-dicarbonyl radical cations generated by the reaction of NHCs with oxalyl chloride are remarkably persistent even in an aqueous solution for several months. They are also highly stable even under physiological conditions, making them particularly attractive potential candidates for organic MRI contrast agents. We hope that this Account will serve as a guide for the future development of stable NHC-derived organic radicals and draw the attention of the synthetic community to their potential applications in material science.

GPU-accelerated study of the inertial cavitation threshold in viscoelastic soft tissue using a dual-frequency driving signal

Inertial cavitation thresholds under two forms of ultrasonic excitation (the single- and dual-frequency ultrasound modes) are studied numerically. The Gilmore-Akulichev model coupled with the Zener viscoelastic model is used to model the bubble dynamics. The threshold pressures are determined with two criteria, one based on the bubble radius and the other on the bubble collapse speed. The threshold behavior is investigated for different initial bubble sizes, acoustic signal modes, frequencies, tissue viscosities, tissue elasticities, and all their combinations. Due to the large number of parameters and their many combinations (around 1.5 billion for each threshold criterion), all simulations were executed on graphics processing units to speed up the calculations. We used our own code written in the C++ and CUDA C languages. The results obtained demonstrate that using the dual-frequency signal mode can help to reduce the inertial cavitation threshold (in comparison to the single-frequency mode). The criterion based on the bubble size gives a lower threshold than the criterion using the bubble collapse speed. With an increase of the elasticity, the threshold pressure also increases, whereas changing the viscosity has a very small impact on the optimal threshold, unlike the elasticity. A detailed analysis of the optimal ultrasound frequencies for a dual-frequency driving signal found that for viscosities less than 0.02 Pa·s, the first optimal frequency, in general, is much smaller than the second optimal frequency, which can reach 1 MHz. However, for high viscosities, both optimal frequencies are similar and varied in the range 0.01-0.05 MHz. Overall, this study presents a detailed analysis of inertial cavitation in soft tissue under dual-frequency signal excitation. It may be helpful for the further development of different applications of biomedical ultrasound.

Weakly nonlinear propagation of focused ultrasound in bubbly liquids with a thermal effect: Derivation of two cases of Khokolov-Zabolotskaya-Kuznetsoz equations

A physico-mathematical model composed of a single equation that consistently describes nonlinear focused ultrasound, bubble oscillations, and temperature fluctuations is theoretically proposed for microbubble-enhanced medical applications. The Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation that has been widely used as a simplified model for nonlinear propagation of focused ultrasound in pure liquid is extended to that in liquid containing many spherical microbubbles, by applying the method of multiple scales to the volumetric averaged basic equations for bubbly liquids. As a result, for two-dimensional and three-dimensional cases, KZK equations composed of the linear combination of nonlinear, dissipation, dispersion, and focusing terms are derived. Especially, the dissipation term depends on three factors, i.e., interfacial liquid viscosity, liquid compressibility, and thermal conductivity of gas inside bubbles; the thermal conduction is evaluated by using four types of temperature gradient models. Finally, we numerically solve the derived KZK equation and show a moderate temperature rise appropriate to medical applications.

Investigation of hardware and software techniques to enhance the characteristics of focused ultrasound (FUS) spectra

Objective. Microbubble cavitation generated by focused ultrasound (FUS) can induce safe blood-brain-barrier (BBB) opening allowing therapeutic drug passage. Spectral changes in the hydrophone sensor signal are currently used to distinguish stable cavitation from inertial cavitation that can damage the BBB. Gibbs’ ringing, peak intensity loss and peak width increase are well-known distortions evident when using the discrete Fourier transform (DFT) to transform data containing a few hundred points. We investigate overcoming the fact that FUS time signals (10 ms providing 312 500 points sampled at 32 ns intervals) can generate such sharp spectral peaks that variations in their DFT-related distortions can significantly impact the values of the key metrics used for cavitation characterization. Approach. We introduce low-pass filter hardware to improve how the analogue to digital convertor handles high-frequency noise components and the orders of magnitude differences between FUS harmonic intensities. We investigate the enhanced FUS spectral stability and resolution obtained from a new technique, physical sparsification (PH-SP), customized to the a-priori information that all key FUS components are harmonically related. Results are compared with standard DFT optimizations involving time data windowing and Fourier interpolation. Main results. A new simulation model showed peak intensity, widths and metrics modified by small changes in the transformed signal’s length when removing the noisy starting transient of the FUS hydrophone signal or following minor excitation frequency or sampling rate adjustments. 25%–60% area-under-the-curve changes occurred in phantom studies at different pressure levels. Spectral peak sharpness was best optimized and stabilized with PH-SP. Significance. Special FUS characteristics mean starting transients and minor variations in experimental procedures lead to significant changes in the spectral metrics used to monitor cavitation levels. Customizing PH-SP to these characteristics led to sharper, more stable spectra with the potential to track the impact of microbubble environment changes.

Nanodroplet-Mediated Low-Energy Mechanical Ultrasound Surgery

Mechanical ultrasound surgery methods use short, high-intensity pulses to fractionate tissues. This study reports the development of a two-step technology for low-energy mechanical ultrasound surgery of tissues using nanodroplets to reduce the pressure threshold. Step 1 consists of vaporizing the nanodroplets into gaseous microbubbles via megahertz ultrasound excitation. Then, low-frequency ultrasound is applied to the microbubbles, which turns them into therapeutic warheads that trigger potent mechanical effects in the surrounding tissue. The use of nanoscale nanodroplets coupled with low-frequency ultrasound reduces the pressure threshold required for mechanical ultrasound surgery by an order of magnitude. In addition, their average diameter of 300 nm can overcome challenges associated with the size of microbubbles. Optimization experiments were performed to determine the ultrasound parameters for nanodroplet vaporization and the subsequent microbubble implosion processes. Optimal vaporization was obtained when transmitting a 2-cycle excitation pulse at a center frequency of 5 MHz and a peak negative pressure of 4.1 MPa (mechanical index = 1.8). Low-frequency insonation of the generated microbubbles at a center frequency of 850, 250 or 80 kHz caused enhanced contrast reduction at a center frequency of 80 kHz, compared with the other frequencies, while operating at the same mechanical index of 0.9. Nanodroplet-mediated insonation of ex vivo chicken liver samples generated mechanical damage. Low-frequency treatment at a mechanical index of 0.9 and a center frequency of 80 kHz induced the largest lesion area (average of 0.59 mm²) compared with 250- and 850-kHz treatments with the same mechanical index (average lesions areas of 0.29 and 0.19 mm², respectively, p < 0.001). The two-step approach makes it possible to conduct both the vaporization and implosion stages at mechanical indices below 1.9, thus avoiding undesired mechanical damage. The findings indicate that coupled with low-frequency ultrasound, nanodroplets can be used for low-energy mechanical ultrasound surgery.

Long-Term Outcomes of Implants Placed in Maxillary Sinus Floor Augmentation with Porous Fluorohydroxyapatite (Algipore® FRIOS®) in Comparison with Anorganic Bovine Bone (Bio-Oss®) and Platelet Rich Plasma (PRP): A Retrospective Study

Purpose: The objective of this retrospective study was to evaluate the long-term clinical outcomes of bone regeneration procedures using algae-derived plant hydroxyapatite (Algipore^® FRIOS^®) compared with demineralized anorganic bovine bone (Bio-Oss^®), in combination with autologous blood-derived PRP. Materials and Methods: Partially edentulous patients with severe atrophy of posterior maxillary treated by means of the split bone technique in a two-stage grafting procedures were observed for up to seven years after implants placement. After surgeries, the natural porous fluorohydroxyapatite (FHA) (Algipore^® FRIOS^®; Group, n = 29) or anorganic bovine bone (Bio-Oss^® Group, n = 28) with autogenous bone in a 50:50 composite ratio with PRP, were administered in a 2.8-mm critical-size defect (CSD). Four months later, implants were placed at second-stage surgery. Results: A sample of fifty-seven consecutive patients who required sinus augmentation was included in the study, and 57 implants were placed. There was no drop out or loss of follow-up of any case. Clinical and radiographic examinations revealed a comparable pattern of newly formed bone in both groups after seven years of functional loading for implants placed after sinus augmentation using porous fluorohydroxyapatite and anorganic bovine bone. No significant difference in marginal bone loss was found around implants in both groups. Conclusions: The favorable implant outcomes suggest both biomaterials are suitable for sinus grafting in severely atrophic maxillae.

Recognition of Biological Tissue Denaturation Based on Improved Multiscale Permutation Entropy and GK Fuzzy Clustering

Recognition of biological tissue denaturation is a vital work in high-intensity focused ultrasound (HIFU) therapy. Multiscale permutation entropy (MPE) is a nonlinear signal processing method for feature extraction, widely applied to the recognition of biological tissue denaturation. However, the typical MPE cannot derive a stable entropy due to intensity information loss during the coarse-graining process. For this problem, an improved multiscale permutation entropy (IMPE) is proposed in this work. IMPE is obtained through refining and reconstructing MPE. Compared with MPE, the IMPE overcomes the deficiency of amplitude information loss due to the coarse-graining process when computing signal complexity. Through the simulation of calculating MPE and IMPE from white Gaussian noise, it is found that the entropy derived by IMPE is more stable than that derived by MPE. The processing method based on IMPE feature extraction is applied to the experimental ultrasonic scattered echo signals in HIFU treatment. Support vector machine and Gustafson–Kessel fuzzy clustering based on MPE and IMPE feature extraction are also used for biological tissue denaturation classification and recognition. The results calculated from the different combination algorithms show that the recognition of biological tissue denaturation based on IMPE-GK clustering is more reliable with the accuracy of 95.5%.

Numerical Study of Bubble Cloud and Thermal Lesion Evolution During Acoustic Droplet Vaporization Enhanced HIFU Treatment

Acoustic droplet vaporization (ADV) has been proven to enhance high intensity focused ultrasound (HIFU) thermal ablation of tumor. It has also been demonstrated that triggering droplets before HIFU exposure could be a potential way to control both the size and the shape of the thermal lesion. In this paper, a numerical model is proposed to predict the thermal lesion created in ADV enhanced HIFU treatment. Bubble oscillation was coupled into a viscoelastic medium in the model to more closely represent real applications in tissues. Several physical processes caused by continuous wave ultrasound and elevated temperature during the HIFU exposure were considered, including rectified diffusion, gas solubility variation with temperature in the medium, and boiling. Four droplet concentrations spanning two orders of magnitude were calculated. The bubble cloud formed from triggering of the droplets by the pulse wave ultrasound, along with the evolution of the shape and location of the bubble cloud and thermal lesion during the following continuous wave exposure was obtained. The increase of bubble void fraction caused by continuous wave exposure was found to be consistent with the experimental observation. With the increase of droplet concentration, the predicted bubble cloud shapes vary from tadpole to triangular and double triangular, while the thermal lesions move toward the transducer. The results show that the assumptions used in this model increased the accuracy of the results. This model may be used for parametrical study of ADV enhanced HIFU treatment and be further used for treatment planning and optimization in the future.

Localized motion imaging for monitoring HIFU therapy: Comparison of modulating frequencies and utilization of square modulating wave

High-intensity focused ultrasound (HIFU) has been successfully used as a minimally invasive cancer therapy method. For monitoring the therapy, the amplitude-modulated (AM) localized motion imaging (LMI) method had been proposed. This paper compares the performance of AM-LMI while using different sine modulating wave frequencies and proposes the utilization of square modulating waves to gain the advantages of both high and low modulating frequencies. A single element therapy transducer with a 2 MHz central frequency was driven by sine modulating waves with different frequencies (approximate 34, 67, 102, 168, and 201 Hz) and by square modulating waves with two frequencies (34 and 67 Hz). An imaging probe with a 5 MHz central frequency and a 20 MHz sampling frequency was mounted in the center hole of the therapy transducer to acquire pulse-echo data, which were used to estimate the tissue oscillation amplitude induced by the acoustic radiation force of the HIFU beam. The decrease ratio of the oscillation amount was then utilized to estimate the coagulated lesion length during the therapy. The comparison of modulating frequencies demonstrated that a higher frequency could bring higher sensitivity to small lesions, while a lower frequency not only gives greater noise robustness but also promotes the ability to estimate lengths of larger lesions. The utilization of a square modulating wave demonstrated its utility to produce tissue oscillation with multiple frequencies and gain the advantages of both high and low modulating frequencies.

Sonication of the Anterior Thalamus With MRI-Guided Transcranial Focused Ultrasound (tFUS) Alters Pain Thresholds in Healthy Adults: A Double-Blind, Sham-Controlled Study

(Appeared originally in Brain Stimulation 2020; 13:1805-1812) Reprinted with permission from Elsevier.

Ultrasound Application in Physical Therapy of Dogs: Comparative Study

The application of ultrasonic methods in veterinary medicine, especially in the therapy of dogs, is the main objective of this study. We compared the frequency of therapeutic ultrasound using in rehabilitation as well as in microsurgical interventions of dogs in Slovakian and Hungarian veterinary practices. Regarding to the evaluation of survey realized in restricted regions, the ultrasound therapies and interventions are currently used in Slovakia less than in Hungary. Our study could start a change in this unfavourable aspect in Slovakian veterinary medicine and contribute to a better promotion of ultrasound application in the therapy of animals.

Current Landscape of Sonodynamic Therapy for Treating Cancer

Simple Summary

Recently, ultrasound has advanced in its treatment opportunities. One example is sonodynamic therapy, a minimally invasive anti-cancer therapy involving a chemical sonosensitizer and focused ultrasound. The combination of the ultrasound and chemical sonosensitizer amplifies the drug’s ability to target cancer cells. Combining multiple chemical sonosensitizers with ultrasound can create a synergistic effect that could effectively disrupt tumorigenic growth, induce cell death, and elicit an immune response. This review provides an oversight of the application of this treatment to various types of cancer, including prostate cancer, glioma, and pancreatic ductal adenocarcinoma tumors.

Abstract

Recent advancements have tangibly changed the cancer treatment landscape. However, curative therapy for this dreadful disease remains an unmet need. Sonodynamic therapy (SDT) is a minimally invasive anti-cancer therapy involving a chemical sonosensitizer and focused ultrasound. A high-intensity focused ultrasound (HIFU) beam is used to destroy or denature targeted cancer tissues. Some SDTs are based on unfocused ultrasound (US). In some SDTs, HIFU is combined with a drug, known as a chemical sonosensitizer, to amplify the drug’s ability to damage cancer cells preferentially. The mechanism by which US interferes with cancer cell function is further amplified by applying acoustic sensitizers. Combining multiple chemical sonosensitizers with US creates a substantial synergistic effect that could effectively disrupt tumorigenic growth, induce cell death, and elicit an immune response. Therefore, the minimally invasive SDT treatment is currently attracting attention. It can be combined with targeted therapy (double-targeting cancer therapy) and immunotherapy in the future and is expected to be a boon for treating previously incurable cancers. In this paper, we will consider the current state of this therapy and discuss parts of our research.

Efficacy and Safety of High-Intensity, High-Frequency, Parallel Ultrasound Beams for Fine Lines and Wrinkles

BACKGROUND

Ultrasound energy has been used for cutaneous rejuvenation, including treatment of fine lines and wrinkles. Ultrasound waves of high intensity can induce thermal injury in the dermis, which causes tissue coagulation and remodeling.

OBJECTIVE

To examine the safety and utility of a novel ultrasound device that uses high-intensity, high-frequency, parallel ultrasound beams to improve fine lines and wrinkles of the face and neck.

MATERIALS AND METHODS

A prospective, multicenter, clinical study investigated the utility of this novel ultrasound device to improve fine lines and wrinkles. Sixty subjects were enrolled for single treatment to the face and neck.

RESULTS

Fifty-eight subjects completed the study. The mean age was 58 years, and 87.9% were women. Fitzpatrick skin Types I to VI were represented. Assessments compared 12-week follow-up with baseline. Two blinded reviewers agreed in identifying pretreatment and post-treatment photographs for 78% of subjects. There was significant improvement of 1 to 3 Fitzpatrick Wrinkle and Elastosis Scale units in 86% of subjects. For investigator global improvement scores, 88% of subjects had improvement. Overall, 72% of subjects noted improvement, and the majority were satisfied. There were no device-related adverse events.

CONCLUSION

Treatment with a novel ultrasound device that uses high-intensity, high-frequency, parallel ultrasound beams safely improved the clinical appearance of fine lines and wrinkles of the face and neck.

A Review of High-Intensity Focused Ultrasound in Urology

This review provides an introduction to high-intensity focused ultrasound (HIFU) and reviews its historical and current use in urological surgery. Current and historical literature (1927-2020), including that describing trials and review articles in the medical and ultrasonic literature, has been reviewed, using Pub Med and Cochrane search engines. HIFU is currently one of a number of treatments for prostate cancer, both as a primary treatment that can be repeated, and as a salvage treatment post-radiotherapy. HIFU is not yet sufficiently mature to be a standard treatment for renal cancer or other urological diseases, although there has been some success in early clinical trials. As the technology improves, this situation is likely to change. HIFU has been understood as a concept for a century, and has been applied in experimental use for half that time. It is now an accepted treatment with low morbidity in many diseases outside the scope of this review. In urological surgery, prostate HIFU is accepted as a localised treatment in selected cases, with potentially fewer side effects than other localised therapies. Currently the treatment for renal cancer is hindered by the perinephric fat and the position of the kidneys behind the ribs; however, as the technology improves with image fusion, faster treatments, and the ability with phased array transducers and motion compensation to overcome the problems caused by the ribs and breathing, successful treatment of kidney tumours will become more of a reality. In due course, there will be a new generation of machines for treating prostate cancer. These devices will further minimise the side effects of radical treatment of prostate cancer.

Evolvable Acoustic Field Generated by a Transducer with 3D-Printed Fresnel Lens

Evolvable acoustic fields are considered an effective method for solving technical problems related to fields such as biological imaging, particle manipulation, drug therapy and intervention. However, because of technical difficulties and the limited technology available for realizing flexible adjustments of sound fields, few studies have reported on this aspect in recent years. Herein, we propose a novel solution, using a Fresnel lens-focused ultrasonic transducer for generating excited-signal-dependent acoustic pressure patterns. Finite element analysis (FEA) is used to predict the performance of a transducer with a Fresnel lens. The Fresnel lens is printed using 3D additive manufacturing. Normalized intensity maps of the acoustic pressure fields are characterized from the Fresnel lens-focused transducer under various numbers of excited-signal cycles. The results demonstrate that under different cycle excitations, a temporal evolution acoustic intensity can be generated and regulated by an ultrasound transducer with a 3D Fresnel lens. This acoustical pattern control method is not only simple to realize but also has considerable application prospects.

Devastated Bladder Outlet in Pelvic Cancer Survivors: Issues on Surgical Reconstruction and Quality of Life

Bladder outlet obstruction following treatment of pelvic cancer, predominantly prostate cancer, occurs in 1-8% of patients. The high incidence of prostate cancer combined with the long-life expectancy after treatment has increased concerns with cancer survivorship care. However, despite increased oncological cure rates, these adverse events do occur, compromising patients' quality of life. Non-traumatic obstruction of the posterior urethra and bladder neck include membranous and prostatic urethral stenosis and bladder neck stenosis (also known as contracture). The devastated bladder outlet can result from benign conditions, such as neurogenic dysfunction, trauma, iatrogenic causes, or more frequently from complications of oncologic treatment, such as prostate, bladder and rectum. Most posterior urethral stenoses may respond to endoluminal treatments such as dilatation, direct vision internal urethrotomy, and occasionally urethral stents. Although surgical reconstruction offers the best chance of durable success, these reconstructive options are fraught with severe complications and, therefore, are far from being ideal. In patients with prior RT, failed reconstruction, densely fibrotic and/or necrotic and calcified posterior urethra, refractory incontinence or severe comorbidities, reconstruction may not be either feasible or recommended. In these cases, urinary diversion with or without cystectomy is usually required. This review aims to discuss the diagnostic evaluation and treatment options for patients with bladder outlet obstruction with a special emphasis on patients unsuitable for reconstruction of the posterior urethra and requiring urinary diversion.

High-Frequency Focused Ultrasound on Quality Traits of Bovine Triceps brachii Muscle

This aim of this study was to evaluate the effect of high-frequency focused ultrasound (HFFU) on quality traits of bovine Triceps brachii. Four treatments (0, 10, 20, and 30 min) of HFFU (2 MHz and 1.5 W/cm²) were applied to bovine T. brachii muscle. Immediately after treatment, evaluations of color, pH, drip loss, water holding capacity, and shear force in meat were undertaken. The application of HFFU slightly decreased (p < 0.05) the redness of meat. In addition, a significant (p < 0.05) decrease in the shear force of meat was observed after the application of HFFU at 30 min. No effect (p > 0.05) was observed on other color parameters, drip loss, and water holding capacity of meat. Overall, HFFU improved beef tenderness without negative impacts on color, pH, drip loss, and water holding capacity of meat. HFFU offers the option of tenderizing specific muscles or anatomical regions of the beef carcass. These findings provide new insights into the potential application of ultrasound in meat processing.

Oncologic outcome of salvage high-intensity focused ultrasound (HIFU) in radiorecurrent prostate cancer. A systematic review

INTRODUCTION

External Beam Radiation Therapy (EBRT) is one of the option available for the treatment of clinically localized prostate cancer. In patients with radiorecurrent localized prostate cancer, Androgen Deprivation Therapy (ADT) is one of the most common therapeutic strategies. However, in the last decades, other salvage treatment options have been investigated, such as brachytherapy, cryoablation and High Intensity Focused Ultrasound (Hifu).

MATERIAL AND METHODS

The oncologic outcome of Hifu in a salvage setting after EBRT failure was investigated. We reviewed the literature from 2005 to 2020 in order to report the oncologic outcome of the technique.

RESULTS

A total of 1241 patients were analyzed, with a mean age of 68.6 years and a PSA value of 5.87 ng/mL before treatment. Mean follow-up was 24.3 months after treatment, ranging from 3 to 168 months.

CONCLUSION

Our review of the literature revealed that salvage Hifu is effective in the treatment of radiorecurrent clinically localized prostate cancer, with an overall survival of 85.2% at 5 years.

Oxford's clinical experience in the development of high intensity focused ultrasound therapy

High Intensity Focused Ultrasound (HIFU) capably bridges the disciplines of surgery, oncology and biomedical engineering science. It provides the precision associated with a surgical tool whilst remaining a truly non-invasive technique. Oxford has been a centre for both clinical and preclinical research in HIFU over the last twenty years. Research into this technology in the UK has a longer history, with much of the early research being carried out by Professor Gail ter Haar and her team at the Institute of Cancer Research at Sutton in Surrey. A broad range of potential applications have been explored extending from tissue ablation to novel drug delivery. This review presents Oxford's clinical studies and applications for the development of this non-invasive therapy. This includes treatment of solid abdominal tumours comprising those of the liver, kidney, uterus, pancreas, pelvis and prostate. It also briefly introduces preclinical and translational works that are currently being undertaken at the Institute of Biomedical Engineering, University of Oxford. The safety, wide tolerability and effectiveness of this technology is comprehensively demonstrated across these studies. These results can facilitate the incorporation of HIFU as a key clinical management strategy.

Nonlinearity of the coefficient of thermal expansion in brain tissue

The coefficient of thermal expansion (CTE) in biological tissues is an integral parameter behind the application of electromagnetic energy to biomedical technologies; however, its behavior is far from being fully characterized. In this study, we apply digital image correlation (DIC) to non-invasively measure the microscale thermal expansions of recently excised embryonic E18 rodent brain tissue slices. Although the CTE has been measured previously in soft tissues, the literature surrounding the expansion of brain tissue remains sparse. Previous work in measuring the thermal expansion behavior of soft tissue often simplifies the results into a single measurement of a linear CTE parameter and fails to convey the temperature-dependent nonlinearity that exists. In this work, we demonstrate that: (1) the coefficient of brain tissue is more similar to fat than blood, and (2) there exists a significant nonlinear increase in CTE at physiologically-relevant temperatures. This suggests some limitations with the interpretation of previously reported values of the CTE, which are often measured at room temperature.

Numerical study on sector-vortex phased irradiation method using annular array transducer in High-Intensity Focused Ultrasound treatment

Sector-vortex phased irradiation from annular array transducer was numerically studied with breast model constructed from MRI data of real patient. Phase compensation (PC) based on time reversal pre-computation was applied in order to handle phase delay caused by heterogeneity of breast tissues, and results showed great effectiveness on single-focus case, insignificant effectiveness on multi-focus cases with 4 and 8 phase-sectors, but ineffectiveness on multi-focus case with 12 phase-sectors, where enormous undesired outer ablation occurred. For single-focus case, phase compensation not only produced real focus very close to targeted site (0.1 mm deviation), but also decreased thermal peak ratio (outer/focal) largely by 30%. However, phase compensation did not increase total ablated size. For multi-focus cases with 4 and 8 phase-sectors, deformed focal shapes by tissue heterogeneity were restored by phase compensation, but the 4-phase-sector case had higher thermal peak ratio and smaller ablation than 8-phase-sector case for strong cancelling effect between phase-sector borders. Ineffectiveness of phase compensation on multi-focus case with 12 phase-sectors had three considerable reasons. 1st, inequality of piezo-element number between sectors; 2nd, heterogeneous attenuation of breast model; 3rd, insufficient number of piezo-elements per sector; where the 2nd reason originated from breast model, and other two reasons were related to array transducer. This research gave several preliminary indications. 1st, ineffectiveness of phase compensation occurs on case with large phase-sector number when using annular array transducer; 2nd, with same input energy and same irradiation time, sector-vortex phased irradiation creates smaller focal ablation, but withstands longer than single-focus irradiation free of outer ablation; 3rd, phase-difference π between neighboring phase-sectors is disadvantageous because of energy loss; 4th, phase compensation is effective on single-focus for improving pinpoint ablation but not for increasing total ablated size.

Drug Delivery by Ultrasound-Responsive Nanocarriers for Cancer Treatment

Conventional cancer chemotherapies often exhibit insufficient therapeutic outcomes and dose-limiting toxicity. Therefore, there is a need for novel therapeutics and formulations with higher efficacy, improved safety, and more favorable toxicological profiles. This has promoted the development of nanomedicines, including systems for drug delivery, but also for imaging and diagnostics. Nanoparticles loaded with drugs can be designed to overcome several biological barriers to improving efficiency and reducing toxicity. In addition, stimuli-responsive nanocarriers are able to release their payload on demand at the tumor tissue site, preventing premature drug loss. This review focuses on ultrasound-triggered drug delivery by nanocarriers as a versatile, cost-efficient, non-invasive technique for improving tissue specificity and tissue penetration, and for achieving high drug concentrations at their intended site of action. It highlights aspects relevant for ultrasound-mediated drug delivery, including ultrasound parameters and resulting biological effects. Then, concepts in ultrasound-mediated drug delivery are introduced and a comprehensive overview of several types of nanoparticles used for this purpose is given. This includes an in-depth compilation of the literature on the various in vivo ultrasound-responsive drug delivery systems. Finally, toxicological and safety considerations regarding ultrasound-mediated drug delivery with nanocarriers are discussed.

Phasor Wave-Field Simulation Providing Direct Access to Instantaneous Frequency: A Demonstration for a Damped Elastic Wave Simulation

In this work, we describe and simulate a wave field as a phasor field by simultaneously propagating its real and imaginary parts. In this way, the unique phase angle is directly available, and its time derivative determines the instantaneous frequency. We utilize the concept to describe damping in elastic wave propagation, which is of high importance in several engineering and research disciplines, ranging from earth science and medical diagnosis to physics.

Investigation of feasibility of noise suppression method for cavitation-enhanced high-intensity focused ultrasound treatment

In high-intensity focused ultrasound (HIFU) treatment, a method that monitors tissue changes while irradiating therapeutic ultrasound is needed to detect changes in the order of milliseconds due to thermal coagulation and the presence of cavitation bubbles. The new filtering method in which only the HIFU noise was reduced while the tissue signals remained intact was proposed in the conventional HIFU exposure in our preliminary study. However, HIFU was irradiated perpendicular to the direction of the imaging ultrasound in the preliminary experiment, which was believed to be impractical. This study investigated the efficacy of the proposed method a parallel setup, in which both HIFU and imaging beams have the same axis just as in a practical application. In addition, this filtering algorithm was applied to the "Trigger HIFU" sequence in which ultrasound-induced cavitation bubbles were generated in the HIFU focal region to enhance heating. In this setup and sequence, HIFU noise level was increased and the summation or difference tone induced by the interaction of HIFU waves with the imaging pulse has the potential to affect this proposed method. Ex-vivo experiments proved that the HIFU noise was selectively eliminated by the proposed filtering method in which chaotic acoustic signals were emitted by the cavitation bubbles at the HIFU focus. These results suggest that the proposed method was practically efficient for monitoring tissue changes in HIFU-induced cavitation bubbles.