Pathological changes in human malignant carcinoma treated with high-intensity focused ultrasound

Numerical studies on shortening the duration of HIFU ablation therapy and their experimental validation

High Intensity Focused Ultrasound (HIFU) is used in clinical practice for thermal ablation of malignant and benign solid tumors located in various organs. One of the reason limiting the wider use of this technology is the long treatment time resulting from i.a. the large difference between the size of the focal volume of the heating beam and the size of the tumor. Therefore, the treatment of large tumors requires scanning their volume with a sequence of single heating beams, the focus of which is moved in the focal plane along a specific trajectory with specific time and distance interval between sonications. To avoid an undesirable increase in the temperature of healthy tissues surrounding the tumor during scanning, the acoustic power and exposure time of each HIFU beam as well as the time intervals between sonications should be selected in such a way as to cover the entire volume of the tumor with necrosis as quickly as possible. This would reduce the costs of treatment. The aim of this study was to quantitatively evaluate the hypothesis that selecting the average acoustic power and exposure time for each individual heating beam, as well as the temporal intervals between sonications, can significantly shorten treatment time. Using 3D numerical simulations, the dependence of the duration of treatment of a tumor with a diameter of 5 mm or 9 mm (requiring multiple exposure to the HIFU beam) on the sonication parameters (acoustic power, exposure time) of each single beam capable of delivering the threshold thermal dose (CEM43 = 240 min) to the treated tissue volume was examined. The treatment duration was determined as the sum of exposure times to individual beams and time intervals between sonications. The tumor was located inside the ex vivo tissue sample at a depth of 12.6 mm. The thickness of the water layer between the HIFU transducer and the tissue was 50 mm. The sonication and scanning parameters selected using the developed algorithm shortened the duration of the ablation procedure by almost 14 times for a 5-mm tumor and 20 times for a 9-mm tumor compared to the duration of the same ablation plan when a HIFU beam was used of a constant acoustic power, constant exposure time (3 s) and constant long time intervals (120 s) between sonications. Results of calculations of the location and size of the necrotic lesion formed were experimentally verified on ex vivo pork loin samples, showing good agreement between them. In this way, it was proven that the proper selection of sonication and scanning parameters for each HIFU beam allows to significantly shorten the time of HIFU therapy.

Functionalized Nanomaterials for Inhibiting ATP-Dependent Heat Shock Proteins in Cancer Photothermal/Photodynamic Therapy and Combination Therapy

Phototherapies induced by photoactive nanomaterials have inspired and accentuated the importance of nanomedicine in cancer therapy in recent years. During these light-activated cancer therapies, a nanoagent can produce heat and cytotoxic reactive oxygen species by absorption of light energy for photothermal therapy (PTT) and photodynamic therapy (PDT). However, PTT is limited by the self-protective nature of cells, with upregulated production of heat shock proteins (HSP) under mild hyperthermia, which also influences PDT. To reduce HSP production in cancer cells and to enhance PTT/PDT, small HSP inhibitors that can competitively bind at the ATP-binding site of an HSP could be employed. Alternatively, reducing intracellular glucose concentration can also decrease ATP production from the metabolic pathways and downregulate HSP production from glucose deprivation. Other than reversing the thermal resistance of cancer cells for mild-temperature PTT, an HSP inhibitor can also be integrated into functionalized nanomaterials to alleviate tumor hypoxia and enhance the efficacy of PDT. Furthermore, the co-delivery of a small-molecule drug for direct HSP inhibition and a chemotherapeutic drug can integrate enhanced PTT/PDT with chemotherapy (CT). On the other hand, delivering a glucose-deprivation agent like glucose oxidase (GOx) can indirectly inhibit HSP and boost the efficacy of PTT/PDT while combining these therapies with cancer starvation therapy (ST). In this review, we intend to discuss different nanomaterial-based approaches that can inhibit HSP production via ATP regulation and their uses in PTT/PDT and cancer combination therapy such as CT and ST.

Clinical translation of abdominal histotripsy: a review of preclinical studies in large animal models

Histotripsy is an emerging noninvasive, non-thermal, and non-ionizing focused ultrasound (US) therapy that can be used to destroy targeted tissue. Histotripsy has evolved from early laboratory prototypes to clinical systems which have been comprehensively evaluated in the preclinical environment to ensure safe translation to human use. This review summarizes the observations and results from preclinical histotripsy studies in the liver, kidney, and pancreas. Key findings from these studies include the ability to make a clinically relevant treatment zone in each organ with maintained collagenous architecture, potentially allowing treatments in areas not currently amenable to thermal ablation. Treatments across organ capsules have proven safe, including in anticoagulated models which may expand patients eligible for treatment or eliminate the risk associated with taking patients off anti-coagulation. Treatment zones are well-defined with imaging and rapidly resorb, which may allow improved evaluation of treatment zones for residual or recurrent tumor. Understanding the effects of histotripsy in animal models will help inform physicians adopting histotripsy for human clinical use.

The dose of focused ultrasound ablation surgery (FUAS) for unresectable pancreatic cancer is predictable: A multicenter retrospective study

To analyze the influencing factors of energy efficiency factors (EEF) in focused ultrasound ablation surgery (FUAS) for unresectable pancreatic cancer and build a dosimetry model. The patients with unresectable pancreatic cancer that underwent FUAS were enrolled from 3 clinical centers between June 2015 and June 2022 for retrospective analysis. The significance of the factors with the potential to affect the EEF was assessed, correlations among the factors were analyzed, and the accuracy of the prediction models established by the factors containing different imaging features was compared. From a total of 236 cases, 215 cases were screened for study, EEF was significantly correlated with mode of anesthesia, grayscale change, tumor volume, tumor location, the distance from the tumor center to skin, contrast-enhanced computer tomography enhancement type, T2-weighted imaging fat suppression signal intensity and contrast-enhanced T1-weighted imaging enhancement type on magnetic resonance imaging. The resultant multiple regression models of EEF achieved significance, contains predictors of Tumor volume, the distance from tumor center to skin, T2-weighted imaging fat suppression signal intensity, and contrast-enhanced T1-weighted imaging enhancement type had better goodness of fit. Compared with CT, the EEF prediction model established by adding magnetic resonance imaging features showed better prediction in FUAS treatment of unresectable pancreatic cancer.

Essential Tremor - Deep Brain Stimulation vs. Focused Ultrasound

INTRODUCTION

Essential Tremor (ET) is one of the most common tremor syndromes typically presented as action tremor, affecting mainly the upper limbs. In at least 30-50% of patients, tremor interferes with quality of life, does not respond to first-line therapies and/or intolerable adverse effects may occur. Therefore, surgery may be considered.

AREAS COVERED

In this review, the authors discuss and compare unilateral ventral intermedius nucleus deep brain stimulation (VIM DBS) and bilateral DBS with Magnetic Resonance-guided Focused Ultrasound (MRgFUS) thalamotomy, which comprises focused acoustic energy generating ablation under real-time MRI guidance. Discussion includes their impact on tremor reduction and their potential complications. Finally, the authors provide their expert opinion.

EXPERT OPINION

DBS is adjustable, potentially reversible and allows bilateral treatments; however, it is invasive requires hardware implantation, and has higher surgical risks. Instead, MRgFUS is less invasive, less expensive, and requires no hardware maintenance. Beyond these technical differences, the decision should also involve the patient, family, and caregivers.

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.

Focused ultrasound ablation surgery for multiple breast fibroadenomas: pathological and follow-up results

OBJECTIVE

To investigate the histopathological findings and follow-up outcome of focused ultrasound ablation surgery (FUAS) treatment of multiple fibroadenomas (FA).

METHODS

A total of 20 patients with 101 multiple FAs were enrolled. After one session FUAS ablation, 21 lesions (≥15.0 mm) were surgically removed within one week for histopathological analysis, including 2, 3, 5-triphenyltetrazolium chloride (TTC) staining, H&E staining, nicotinamide adenine dinucleotide (NADH) -flavretin enzyme staining, Transmission electron microscope (TEM) and scanning electron microscope (SEM). The remaining 80 lesions were followed up at 3, 6 and 12 months after treatment.

RESULTS

All ablation procedures were performed successfully. Pathologic findings showed that irreversible damage of FA was confirmed. TTC, H&E and NADH staining and TEM/SEM demonstrated tumor cell death and tumor structural destruction at the gross, cellular, and subcellular levels, respectively. The median shrinkage rate at 12 months post-FUAS was 66.4 (43.6, 89.5) %.

CONCLUSION

Histopathological analysis for FAs after FUAS treatment proved that FUAS could effectively induce irreversible coagulative necrosis of FA, and the tumor volume would gradually shrink in follow-up. FUAS was safe and effective to treat multiple FAs with good cosmesis.Key pointsThis study was the first study of detailed histopathological analysis for FAs after FUAS treatment.FUAS can effectively induce irreversible coagulative necrosis of fibroadenoma cells.FUAS ablation of multiple fibroadenomas is safe and effective.

Nanomedicine Penetration to Tumor: Challenges, and Advanced Strategies to Tackle This Issue

Nanomedicine has been under investigation for several years to improve the efficiency of chemotherapeutics, having minimal pharmacological effects clinically. Ineffective tumor penetration is mediated by tumor environments, including limited vascular system, rising cancer cells, higher interstitial pressure, and extra-cellular matrix, among other things. Thus far, numerous methods to increase nanomedicine access to tumors have been described, including the manipulation of tumor micro-environments and the improvement of nanomedicine characteristics; however, such outdated approaches still have shortcomings. Multi-functional convertible nanocarriers have recently been developed as an innovative nanomedicine generation with excellent tumor infiltration abilities, such as tumor-penetrating peptide-mediated transcellular transport. The developments and limitations of nanomedicines, as well as expectations for better outcomes of tumor penetration, are discussed in this review.

Combined Therapy Planning, Real-Time Monitoring, and Low Intensity Focused Ultrasound Treatment Using a Diagnostic Imaging Array

Low intensity focused ultrasound (FUS) therapies use low intensity focused ultrasound waves, typically in combination with microbubbles, to non-invasively induce a variety of therapeutic effects. FUS therapies require pre-therapy planning and real-time monitoring during treatment to ensure the FUS beam is correctly targeted to the desired tissue region. To facilitate more streamlined FUS treatments, we present a system for pre-therapy planning, real-time FUS beam visualization, and low intensity FUS treatment using a single diagnostic imaging array. Therapy planning was accomplished by manually segmenting a B-mode image captured by the imaging array and calculating a sonication pattern for the treatment based on the user-input region of interest. For real-time monitoring, the imaging array transmitted a visualization pulse which was focused to the same location as the FUS therapy beam and ultrasonic backscatter from this pulse was used to reconstruct the intensity field of the FUS beam. The therapy planning and beam monitoring techniques were demonstrated in a tissue-mimicking phantom and in a rat tumor in vivo while a mock FUS treatment was carried out. The FUS pulse from the imaging array was excited with an MI of 0.78, which suggests that the array could be used to administer select low intensity FUS treatments involving microbubble activation.

How Did Conventional Nanoparticle-Mediated Photothermal Therapy Become "Hot" in Combination with Cancer Immunotherapy?

Simple Summary

Photothermal therapy (PTT) has become effective through the development of nanoparticle-based photoabsorbers with various functions, such as targeting properties, high light-to-heat conversion, and photostability. Conventional nanoparticle-mediated PTT has attained localized efficiency in cancer treatment by heat-induced apoptosis or necrosis of cancer cells. Currently, such treatment methods evolve into cancer immunotherapy through the induction of immunogenic cell death (ICD). Damage-associated molecular patterns from dead cells by nanoparticle-mediated PTT activate immune cells for systemic anti-cancer effect. In this review, we investigate various nanoparticle-based PTT and compare its methodology to clarify how it undergoes a transition from thermotherapy to immunotherapy.

Abstract

One of the promising cancer treatment methods is photothermal therapy (PTT), which has achieved good therapeutic efficiency through nanoparticle-based photoabsorbers. Because of the various functions of nanoparticles, such as targeting properties, high light-to-heat conversion, and photostability, nanoparticle-mediated PTT successfully induces photothermal damage in tumor tissues with minimal side effects on surrounding healthy tissues. The therapeutic efficacy of PTT originates from cell membrane disruption, protein denaturation, and DNA damage by light-induced heat, but these biological impacts only influence localized tumor areas. This conventional nanoparticle-mediated PTT still attracts attention as a novel cancer immunotherapy, because PTT causes immune responses against cancer. PTT-induced immunogenic cell death activates immune cells for systemic anti-cancer effect. Additionally, the excellent compatibility of PTT with other treatment methods (e.g., chemotherapy and immune checkpoint blockade therapy) reinforces the therapeutic efficacy of PTT as combined immunotherapy. In this review, we investigate various PTT agents of nanoparticles and compare their applications to reveal how nanoparticle-mediated PTT undergoes a transition from thermotherapy to immunotherapy.

Comparison of Dose and Effectiveness of a Single-Session Ultrasound-Guided High-Intensity Focused Ultrasound Ablation of Uterine Fibroids With Different Sizes

PURPOSE

This study aimed to compare the dose and effectiveness of ultrasound-guided high-intensity focused ultrasound (USgHIFU) ablation of uterine fibroids with different sizes and explore the effect of uterine fibroid size on dose, which provided dose evaluation for clinicians in accordance with the size of uterine fibroids.

MATERIALS AND METHODS

A total of 1,000 patients with symptomatic uterine fibroids who received a single-session USgHIFU treatment were enrolled in this study. The size of fibroids was divided into seven groups: 3-4 cm, 4-5 cm, 5-6 cm, 6-7 cm, 7-8 cm, 8-9 cm, and 9-11 cm. The dose was expressed on the basis of the energy efficiency factor (EEF) as the energy required for ablation per unit volume of tissue, and the non-perfused volume ratio (NPVR) was used to assess the effect of HIFU ablation.

RESULTS

The median NPVR of 88.3% (IQR: 80.3%-94.8%) was obtained, and no significant difference was observed among the seven groups. The classification of T2-weighted image signal intensity fibroids in the 4-5 cm group was compared with that in the 6-7 cm and 8-9 cm groups, and the difference was significant (p < 0.05). However, the proportion of T2WI hyperintense signal fibroids had no significant difference among the seven groups (p > 0.05). The median EEF was 3.88 J/mm³, and a significant difference was observed among the seven groups of EEF (p < 0.05). The EEF of groups with a fibroid size less than 6 cm was more than double the EEF of groups with a fibroid size above 6 cm. In addition, the EEF of groups with a fibroid size of 4-5 cm and 3-4 cm was 3-4 times higher than those with a fibroid size above 7 cm (p < 0.05).

CONCLUSIONS

A single-session HIFU ablation for uterine fibroids of 3-11 cm can obtain an NPVR of more than 80%. The EEF decreased with the increase of the size of uterine fibroids. A fibroid size of 6.5 cm was considered as a clinical meaningful point affecting EEF.

Review of clinical tumor ablation advance in Asia

Tumor ablation has been widely applied in Asia, accounting for 44.65% of clinical studies worldwide. We reviewed 5853 clinical studies to provide insight on the advance of tumor ablation in Asia chronologically and geographically among different techniques and organs. Since 1998, tumor ablation application has dramatically evolved in Asia. All kinds of ablation techniques, including percutaneous ethanol injection (PEI), radiofrequency ablation (RFA), microwave ablation (MWA), laser ablation (LA), cryoablation (CA), high-intensity focused ultrasound (HIFU), and irreversible electroporation (IRE), have been applied, with the first application of PEI and the most popular application of RFA. Twenty-five countries and one district in Asia have applied tumor ablation in various organs, including liver, lung, uterus, thyroid, kidney, pancreas, bone, prostate, breast, adrenal gland, lymph node parathyroid, esophagus, etc. Due to the high incidence of tumors as well as advanced economy and technology, East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%). With the enrichment of evidence from large-scale multicenter and randomized control studies, China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques. Therefore, Asia has made active contribution to global tumor ablation therapy.KeypointsKey point 1: Asia accounted for 44.65% of clinical studies worldwide on tumor ablation.Key point 2: Twenty-five countries and one district in Asia have used tumor ablation in various organs, and East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%).Key point 3: China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques.

Temperature Monitoring in Hyperthermia Treatments of Bone Tumors: State-of-the-Art and Future Challenges

Bone metastases and osteoid osteoma (OO) have a high incidence in patients facing primary lesions in many organs. Radiotherapy has long been the standard choice for these patients, performed as stand-alone or in conjunction with surgery. However, the needs of these patients have never been fully met, especially in the ones with low life expectancy, where treatments devoted to pain reduction are pivotal. New techniques as hyperthermia treatments (HTs) are emerging to reduce the associated pain of bone metastases and OO. Temperature monitoring during HTs may significantly improve the clinical outcomes since the amount of thermal injury depends on the tissue temperature and the exposure time. This is particularly relevant in bone tumors due to the adjacent vulnerable structures (e.g., spinal cord and nerve roots). In this Review, we focus on the potential of temperature monitoring on HT of bone cancer. Preclinical and clinical studies have been proposed and are underway to investigate the use of different thermometric techniques in this scenario. We review these studies, the principle of work of the thermometric techniques used in HTs, their strengths, weaknesses, and pitfalls, as well as the strategies and the potential of improving the HTs outcomes.

Characterization and Ex Vivo evaluation of an extracorporeal high-intensity focused ultrasound (HIFU) system

Background

High‐intensity focused ultrasound (HIFU) has been in clinical use for a variety of solid tumors and cancers. Accurate and reliable calibration is in a great need for clinical applications. An extracorporeal clinical HIFU system applied for the investigational device exemption (IDE) to the Food and Drug Administration (FDA) so that evaluation of its characteristics, performance, and safety was required.

Methods

The acoustic pressure and power output was characterized by a fiber optic probe and a radiation force balance, respectively, with the electrical power up to 2000 W. An in situ acoustic energy was established as the clinical protocol at the electrical power up to 500 W. Temperature elevation inside the tissue sample was measured by a thermocouple array. Generated lesion volume at different in situ acoustic energies and pathological examination of the lesions was evaluated ex vivo.

Results

Acoustic pressure mapping showed the insignificant presence of side/grating lobes and pre‐ or post‐focal peaks (≤−12 dB). Although distorted acoustic pressure waveform was found in the free field, the nonlinearity was reduced significantly after the beam propagating through tissue samples (i.e., the second harmonic of −11.8 dB at 500 W). Temperature elevation was <10°C at a distance of 10 mm away from a 20‐mm target, which suggests the well‐controlled HIFU energy deposition and no damage to the surrounding tissue. An acoustic energy in the range of 750–1250 J resulted in discrete lesions with an interval space of 5 mm between the treatment spots. Histology confirmed that the lesions represented a region of permanently damaged cells by heat fixation, without causing cell lysis by either cavitation or boiling.

Conclusions

Our characterization and ex vivo evaluation protocol met the IDE requirement. The in‐situ acoustic energy model will be used in clinical trials to deliver almost consistent energy to the various targets.

The value of dynamic contrast enhanced ultrasound (DCE-US) in monitoring treatment effect of high-intensity focused ultrasound (HIFU) in locally advanced pancreatic cancer (LAPC)

PURPOSE

To evaluate the feasibility of dynamic contrast enhanced ultrasound (DCE-US) in predicting treatment response of high-intensity focused ultrasound (HIFU) in patients with locally advanced pancreatic cancer (LAPC) lesions.

PATIENTS AND METHODS

In this prospective study, 10 patients with pathologically confirmed LAPC lesions (7 men, 3 women; average age, 61.13±5.80 years) were prospectively enrolled. All patients received HIFU treatment with peak intensity at 12000 W/cm2. Contrast enhanced ultrasound (CEUS) was performed with an ACUSON Oxana 2 ultrasound equipment and a 6 C-1 transducer (1-6 Hz). A dose of 2.4 ml SonoVue was injected for each examination. Time intensity curves (TICs) were generated and quantitative analyses were performed by SonoLiver software. B mode ultrasound (BMUS) features, CEUS enhancement patterns, TICs, CEUS quantitative parameters and serum carcinoma antigen 19-9 (CA19-9) levels were compared before and 4 weeks after HIFU treatment. Statistical analyses were performed with SPSS Version 20.0 and GraphPad Prism 5.

RESULTS

While comparing before and after HIFU, no significant difference was obtained on mean size of lesion, BMUS or CEUS features. After HIFU treatment, TICs showed decreased and delayed enhancement. Among all CEUS quantitative parameters, significant decrease could be found in maximum intensity (MI) (60.66±23.95% vs 41.31±26.74%) and mean transit time (mTT) (76.66±47.61 s vs 38.42±28.35 s). CA19-9 level decreased significantly after HIFU (2747.92±4237.41 U/ml vs 715.08±1773.90 U/ml) (P = 0.05).

CONCLUSION

DCE-US combining with quantitative analysis might be a useful imaging method for early treatment response evaluation of HIFU in LAPC lesions.

Quantifying cell death induced by doxorubicin, hyperthermia or HIFU ablation with flow cytometry

Triggered release and targeted drug delivery of potent anti-cancer agents using hyperthermia-mediated focused-ultrasound (FUS) is gaining momentum in the clinical setting. In early phase studies, tissue biopsy samples may be harvested to assess drug delivery efficacy and demonstrate lack of instantaneous cell death due to FUS exposure. We present an optimised tissue cell recovery method and a cell viability assay, compatible with intra-cellular doxorubicin. Flow cytometry was used to determine levels of cell death with suspensions comprised of: (i) HT29 cell line exposed to hyperthermia (30 min at 47 °C) and/or doxorubicin, or ex-vivo bovine liver tissue exposed to (ii) hyperthermia (up to 2 h at 45 °C), or (iii) ablative high intensity FUS (HIFU). Flow cytometric analysis revealed maximal cell death in HT29 receiving both heat and doxorubicin insults and increases in both cell granularity (p < 0.01) and cell death (p < 0.01) in cells recovered from ex-vivo liver tissue exposed to hyperthermia and high pressures of HIFU (8.2 MPa peak-to-peak free-field at 1 MHz) relative to controls. Ex-vivo results were validated with microscopy using pan-cytokeratin stain. This rapid, sensitive and highly quantitative cell-viability method is applicable to the small masses of liver tissue typically recovered from a standard core biopsy (5–20 mg) and may be applied to tissues of other histological origins including immunostaining.

A Novel High-Intensity Focused Ultrasound-Treated Herpes Simplex Virus 2 Vaccine Induces Long-Term Protective Immunity against Lethal Challenge in Mice

High-intensity focused ultrasound (HIFU), a noninvasive ablation therapy that has been widely used clinically in ablation of solid tumors, induces immune sensitization. We therefore in this study investigated whether HIFU treatment could enhance the efficacy of a herpes simplex virus 2 (HSV-2) vaccine. First, we observed that in HSV-2-positive cervical intraepithelial neoplasia (CIN) II patients, HIFU treatment induced significantly higher anti-HSV-2 neutralization response than surgical removal. Next, we tested the efficacy of HIFU-treated, UV-inactivated HSV-2-infected cells as a proof-of-concept vaccine in mice. Our data showed that HIFU-treated formulation significantly enhanced HSV-2 antibody titers and neutralization titers, compared to UV-, microwave (MW)-, or freeze-thaw (FT)-treated formulations. HIFU treatment also promoted the Th1/2 cell-mediated response. A long-term full protection was observed in mice that received the HIFU-treated formulation, and no weight loss was detected. Our findings indicate that the novel application of HIFU in vaccine production may represent a rational way to improve vaccine efficacy.IMPORTANCE High-intensity focused ultrasound (HIFU) is mainly used in tumor ablation and tumor vaccinology study. It has been shown to induce immune sensitization and enhance tumor responsiveness to other therapies. Our study has shown enhanced anti-HSV-2 response in HIFU-treated CIN II patients. Furthermore, in a murine model, we have demonstrated that HIFU-treated HSV-2 vaccine induced long-term protective immunity against lethal challenge. Our findings indicate that the novel application of HIFU in vaccine production may represent a rational way to improve vaccine efficacy.

Acoustic Coupling Quantification in Ultrasound-Guided Focused Ultrasound Surgery: Simulation-Based Evaluation and Experimental Feasibility Study

Adequate acoustic coupling between the therapeutic transducer and the patient's body is essential for safe and efficient focused ultrasound surgery (FUS). There is currently no quantitative method for acoustic coupling verification in ultrasound-guided FUS. In this work, a quantitative method was developed and a related metric was introduced: the acoustic coupling coefficient. This metric associates the adequacy of the acoustic coupling with the reflected signals recorded through an imaging probe during a low-energy sonication. The acoustic coupling issue was simulated in silico and validated through in vitro tests. Our results indicated a sigmoidal behavior of the introduced metric as the contact surface between the coupling system and the patient's skin increases. The proposed method could be a safety-check criterion for verifying the adequacy of the acoustic coupling before starting the FUS treatment, thus ensuring efficient energy transmission to the target and preventing damage to both the patient and the instrumentation.

Biomedical and Pharmacological Uses of Fluorescein Isothiocyanate Chitosan-Based Nanocarriers

Chitosan-based nanocarriers (ChNCs) are considered suitable drug carriers due to their ability to encapsulate a variety of drugs and cross biological barriers to deliver the cargo to their target site. Fluorescein isothiocyanate-labeled chitosan-based NCs (FITC@ChNCs) are used extensively in biomedical and pharmacological applications. The main advantage of using FITC@ChNCs consists of the ability to track their fate both intra and extracellularly. This journey is strictly dependent on the physico-chemical properties of the carrier and the cell types under investigation. Other applications make use of fluorescent ChNCs in cell labeling for the detection of disorders in vivo and controlling of living cells in situ. This review describes the use of FITC@ChNCs in the various applications with a focus on understanding their usefulness in labeled drug-delivery systems.

Feasibility of High-Intensity Focused Ultrasound for Hepatocellular Carcinoma after Stereotactic Body Radiation Therapy: Initial Experience

The purpose of this initial clinical observation was to investigate the safety and effect of high-intensity focused ultrasound (HIFU) for patients with hepatocellular carcinoma (HCC) after stereotactic body radiation therapy (SBRT). Twenty patients who had been treated with SBRT, with 24 local residuals, received HIFU ablation. The changes of periphery blood cell count and serum biochemistry were observed before HIFU and 1 week after. Contrast-enhanced magnetic resonance imaging before HIFU and 2 weeks after was performed to assess the effect of HIFU. All patients received follow-up. The mean ± standard deviation follow-up time was 19.3 ± 18.0 mo. The median survival time and 1-y survival rate were 21 mo and 76.2%. Seventeen residual lesions (70.8%) received complete ablation and seven received partial ablation, with a mean ablation ratio of 75.8% ± 18.2%. No significant differences were found in periphery blood cell counts or serum biochemistry 1 week after HIFU compared with before HIFU. No severe adverse reactions related to HIFU were observed. Thus, we believe that HIFU can safely and effectively ablate residual HCC after SBRT, which may be a feasible option for patients with HCC who have local residuals after SBRT.

Patient-Specific 3-Dimensional Model for High-Intensity Focused Ultrasound Treatment Through the Rib Cage: A Preliminary Study

OBJECTIVES

The purpose of this study was to develop a patient-specific 3-dimensional model for high-intensity focused ultrasound (HIFU) treatment through the rib cage using patient data.

METHODS

Experimental testing to derive parameters used in defining the amount of energy and alteration needed in treatment protocols for upper abdominal disorders under the rib cage was performed. Reconstructed rib cage models based on patient data, tissue-mimicking material phantoms, and magnetic resonance imaging-guided HIFU using a multielement phased array transducer were used in the experiments. Changes in the focal temperature, acoustic power, and acoustic pressure distribution were investigated with and without the presence of the rib cage model. An ExAblate system (InSightec Ltd, Tirat Carmel, Israel) was used to sonicate phantoms by varying the target phantom or rib cage model location.

RESULTS

The effect of the rib cage on the acoustic pressure distribution and acoustic power was closely related to the anatomic structures of the ribs. Thermometry revealed that heating at the focus could be controlled by changing either the power or duration of HIFU application to improve the focal temperature change. The focal temperature change was found to be related to the distance between the rib cage model and focus and the shadow area on the transducer elements covered by the rib cage model in the beam path.

CONCLUSIONS

Experimental results suggest that the rib cage model is a valuable and useful tool that can provide realistic human anatomic structures and properties for evaluating the effects of the rib cage on ultrasound propagation.

An Introduction to High Intensity Focused Ultrasound: Systematic Review on Principles, Devices, and Clinical Applications

Ultrasound can penetrate deep into tissues and interact with human tissue via thermal and mechanical mechanisms. The ability to focus an ultrasound beam and its energy onto millimeter-size targets was a significant milestone in the development of therapeutic applications of focused ultrasound. Focused ultrasound can be used as a non-invasive thermal ablation technique for tumor treatment and is being developed as an option to standard oncologic therapies. High-intensity focused ultrasound has now been used for clinical treatment of a variety of solid malignant tumors, including those in the pancreas, liver, kidney, bone, prostate, and breast, as well as uterine fibroids and soft-tissue sarcomas. Magnetic resonance imaging and Ultrasound imaging can be combined with high intensity focused ultrasound to provide real-time imaging during ablation. Magnetic resonance guided focused ultrasound represents a novel non-invasive method of treatment that may play an important role as an alternative to open neurosurgical procedures for treatment of a number of brain disorders. This paper briefly reviews the underlying principles of HIFU and presents current applications, outcomes, and complications after treatment. Recent applications of Focused ultrasound for tumor treatment, drug delivery, vessel occlusion, histotripsy, movement disorders, and vascular, oncologic, and psychiatric applications are reviewed, along with clinical challenges and potential future clinical applications of HIFU.

Multifunctional Nanodroplets Encapsulating Naphthalocyanine and Perfluorohexane for Bimodal Image-Guided Therapy

Although nanocarriers containing perfluorocarbon (PFC) have been widely investigated as an ultrasound (US) imaging agent and a high intensity focused ultrasound (HIFU) agent, these carriers have suffered from low stability and biocompatibility limiting their further biomedical applications. Here, we developed surface cross-linked polymer nanodroplets as a HIFU therapeutic agent guided by bimodal photoacoustic (PA) and US imaging. Pluronic F127 was reacted with 4-nitrophenyl chloroformate (NPC) and mixed with naphthalocyanine (Nc) in dichloromethane, which was added into the aqueous solution of amine-functionalized six-arm-branched poly(ethylene glycol) (PEG) to form an oil-in-water emulsion for the cross-linking reaction between the terminal NPC of Pluronic F127 and the primary amine of six-arm PEG. The resulting solution was sonicated with liquid perfluorohexane (PFH) to prepare PEG cross-linked Pluronic F127 nanoparticles encapsulating Nc and PFH (Nc/PFH@PCPN). Nc/PFH@PCPN appeared to be stable without any coalescence or vaporization in the physiological condition. Upon the application of HIFU, Nc/PFH@PCPN was vaporized and showed increased US intensity for 180 min. The Nc dye in the nanodroplets enabled the stable encapsulation of PFH and the bimodal US/PA imaging. In vivo PA/US image-guided HIFU ablation therapy confirmed that the nanodroplets increased the cavitation effect, induced necrosis and apoptosis of tumor cells, and reduced tumor growth significantly for 12 days. Taken together, the multifunctional Nc/PFH@PCPN was successfully developed as a new platform for PA/US image-guided HIFU therapy.

Evaluating HIFU-mediated local drug release using thermal strain imaging: Phantom and preliminary in-vivo studies

PURPOSE

High-intensity focused ultrasound (HIFU)-mediated drug release becomes a promising therapeutic technique for treatment of cancer, which has merits of deep penetration, noninvasive approach and nonionizing radiation. However, conventional thermocouple-based approach for treatment monitoring would encounter big challenges such as the viscous heating artifact and difficulty in monitoring in the deep region. In this study, we develop an effective method based on thermal strain imaging (TSI) for the evaluation of HIFU-mediated drug release.

METHODS

Both phantom experiments and preliminary animal experiments were performed to investigate the feasibility of the proposed approach. Doxorubicin (DOX)-loaded cerasomes (HIFU and temperature-sensitive cerasomes, HTSCs) were prepared. In the phantom experiments, the HTSC solution is contained inside a cylindrical chamber within a tissue-mimicking phantom. In the animal experiments, the HTSCs are intravenously injected into tumor-bearing mice. An HIFU transducer is used to trigger DOX release from the HTSCs within the phantom or mice, and TSI is performed during HIFU heating. In the phantom experiments, the accuracy of temperature estimation using TSI is validated by measuring with a thermocouple. In animal experiments, the spatial consistency between the distribution of DOX released within the tumor and the location of the heating region estimated by TSI is validated using a spectrofluorophotometer.

RESULTS

In the phantom experiments, the HTSCs show a burst release of DOX when the temperature of the HTSC solution estimated by TSI reaches about 42°C, which is in agreement with the condition for drug release from the HTSCs. The temperature estimation using TSI has high accuracy with error below 2.5%. In animal experiments, fluorescence imaging of the tumor validates that the heating region of HIFU could be localized by the low-strain region of TSI.

CONCLUSION

The present framework demonstrates a reliable and effective solution to the evaluation of HIFU-mediated local drug delivery.

A Pilot Study for a Quantitative Evaluation of Acoustic Coupling in US-guided Focused Ultrasound Surgery

In Ultrasound-guided High Intensity Focused Ultrasound (USgHIFU) surgery, the verification of the acoustic coupling correctness between the HIFU transducer and the patient's body is a fundamental step for an efficient and safe therapy. Nowadays, clinicians perform this check by qualitative inspecting Ultrasound images. The aim of this study is the introduction of an objective index to quantitively evaluate the coupling on the base of the radiofrequency echo signals acquired during a low-energy HIFU shot. The experimental session involved a tissue mimicking phantom and a robotic system composed by a HIFU therapeutic transducer and a 2D confocal Ultrasound probe. 15 different coupling conditions between the phantom and the transducer were tested: in each of them, the maximum absolute value of the Fourier Transform of the echo signals was computed and employed to determine an Acoustic Coupling (AC) coefficient.This metrics showed a sigmoidal trend between AC coefficient and coupling increase. This curve can be employed as a calibration tool to quantitatively assess the correctness of the therapeutic set-up before starting the HIFU treatment.

Concurrent Osteosarcoma Theranostic Strategy Using Contrast-Enhanced Ultrasound and Drug-Loaded Bubbles

Osteosarcoma (OS) is the most common bone tumor in children and teenagers. The multidrug resistant property of OS produces a major obstacle to chemotherapy, since the effective drug dose cannot be achieved via conventional drug delivery routes without serious systemic cytotoxicity. Microbubbles in conjunction with ultrasound (US) has recently been shown to spatially and temporally permeabilize the cellular membrane, promoting drug penetration into tumors. Here, we investigated whether drug (doxorubicin, DOX)-loaded bubbles (DOX-bubbles) can serve as drug-loaded carriers in combination with US in order to facilitate tumor drug delivery. The proposed bubbles have a high payload capacity (efficiency of 69.4 ± 9.1%, payload of 1.4 mg/mL) for DOX. In vitro data revealed that when used in combination with US (1-MHz), these DOX-bubbles facilitate DOX entering into tumor cells. In tumor-bearing animals, DOX-bubbles + US could provide 3.7-fold suppression of tumor growth compared with the group without insonation (1.8 ± 0.9 cm³ vs. 8.5 ± 2.2 cm³) because of the acceleration of DOX-induced tumor necrosis. In the meantime, the tumor perfusion and volume can be monitored by DOX-bubbles with contrast-enhanced ultrasound imaging. Our data provide useful information in support of translating the use of theranostic US-responsive bubbles for regulated tumor drug delivery into clinical use.

Real-Time Photoacoustic Thermometry Combined With Clinical Ultrasound Imaging and High-Intensity Focused Ultrasound

High-intensity focused ultrasound (HIFU) treatment is a promising non-invasive method for killing or destroying the diseased tissues by locally delivering thermal and mechanical energy without damaging surrounding normal tissues. In HIFU, measuring the temperature at the site of delivery is important for improving therapeutic efficacy, controlling safety, and appropriately planning a treatment. Several researchers have proposed photoacoustic thermometry for monitoring HIFU treatment, but they had many limitations, including the inability to image while the HIFU is on, inability to provide two-dimensional monitoring, and the inability to be used clinically. In this paper, we propose a novel integrated real-time photoacoustic thermometry system for HIFU treatment monitoring. The system provides ultrasound B-mode imaging, photoacoustic structural imaging, and photoacoustic thermometry during HIFU treatment in real-time for both in vitro and in vivo environments, without any interference from the strong therapeutic HIFU waves. We have successfully tested the real-time photoacoustic thermometry by investigating the relationship between the photoacoustic amplitude and the measured temperature with in vitro phantoms and in vivo tumor-bearing mice. The results show the feasibility of a real-time photoacoustic thermometry system for safe and effective monitoring of HIFU treatment.

Magnetically targeted nanoparticles for imaging-guided photothermal therapy of cancer

Over the past several decades, nanocarriers have constituted a vital research area for accurate tumor therapy. Herein, magnetically targeted nanoparticles (IRFes) for photothermal therapy were generated by integrating IR780, a molecule with strong emission and absorption in the NIR spectrum and the ability to produce heat after laser irradiation, with Fe₃O₄ nanoparticles (NPs). These IRFes were guided to the tumor site by the application of an external magnetic field. In particular, the strong NIR absorption of IR780 was used for NIRF imaging, and we also demonstrated effective magnetic targeting for the photothermal ablation of tumors. In vitro cell viability and in vivo antitumor experiments showed that these IRFes can ablate 4T1 cells or transplanted 4T1 cell tumors when exposed to 808 nm laser irradiation and a magnetic field. In vivo experiments showed that IRFes only act on tumors, do not damage other organs and can be used to image tumors. These results demonstrate the enormous potential of local photothermal therapy for cancer under the guidance of external magnetic fields and reveal the prospect for the use of multifunctional nanoparticles in tumor therapy.

Magnetically targeted nanoparticles (IRFes) for photothermal therapy were generated by integrating IR780, a molecule with strong emission and absorption in the NIR spectrum and the ability to produce heat after laser irradiation, with Fe₃O₄ nanoparticles.

Efficient and controllable thermal ablation induced by short-pulsed HIFU sequence assisted with perfluorohexane nanodroplets

A HIFU sequence with extremely short pulse duration and high pulse repetition frequency can achieve thermal ablation at a low acoustic power using inertial cavitation. Because of its cavitation-dependent property, the therapeutic outcome is unreliable when the treatment zone lacks cavitation nuclei. To overcome this intrinsic limitation, we introduced perfluorocarbon nanodroplets as extra cavitation nuclei into short-pulsed HIFU-mediated thermal ablation. Two types of nanodroplets were used with perfluorohexane (PFH) as the core material coated with bovine serum albumin (BSA) or an anionic fluorosurfactant (FS) to demonstrate the feasibility of this study. The thermal ablation process was recorded by high-speed photography. The inertial cavitation activity during the ablation was revealed by sonoluminescence (SL). The high-speed photography results show that the thermal ablation volume increased by ∼643% and 596% with BSA-PFH and FS-PFH, respectively, than the short-pulsed HIFU alone at an acoustic power of 19.5 W. Using nanodroplets, much larger ablation volumes were created even at a much lower acoustic power. Meanwhile, the treatment time for ablating a desired volume significantly reduced in the presence of nanodroplets. Moreover, by adjusting the treatment time, lesion migration towards the HIFU transducer could also be avoided. The SL results show that the thermal lesion shape was significantly dependent on the inertial cavitation in this short-pulsed HIFU-mediated thermal ablation. The inertial cavitation activity became more predictable by using nanodroplets. Therefore, the introduction of PFH nanodroplets as extra cavitation nuclei made the short-pulsed HIFU thermal ablation more efficient by increasing the ablation volume and speed, and more controllable by reducing the acoustic power and preventing lesion migration.

Numerical investigation of the inertial cavitation threshold under multi-frequency ultrasound

Through the introduction of multi-frequency sonication in High Intensity Focused Ultrasound (HIFU), enhancement of efficiency has been noted in several applications including thrombolysis, tissue ablation, sonochemistry, and sonoluminescence. One key experimental observation is that multi-frequency ultrasound can help lower the inertial cavitation threshold, thereby improving the power efficiency. However, this has not been well corroborated by the theory. In this paper, a numerical investigation on the inertial cavitation threshold of microbubbles (MBs) under multi-frequency ultrasound irradiation is conducted. The relationships between the cavitation threshold and MB size at various frequencies and in different media are investigated. The results of single-, dual and triple frequency sonication show reduced inertial cavitation thresholds by introducing additional frequencies which is consistent with previous experimental work. In addition, no significant difference is observed between dual frequency sonication with various frequency differences. This study, not only reaffirms the benefit of using multi-frequency ultrasound for various applications, but also provides a possible route for optimizing ultrasound excitations for initiating inertial cavitation.

Real-Time Spatiotemporal Control of High-Intensity Focused Ultrasound Thermal Ablation Using Echo Decorrelation Imaging in ex Vivo Bovine Liver

The ability to control high-intensity focused ultrasound (HIFU) thermal ablation using echo decorrelation imaging feedback was evaluated in ex vivo bovine liver. Sonications were automatically ceased when the minimum cumulative echo decorrelation within the region of interest exceeded an ablation control threshold, determined from preliminary experiments as -2.7 (log-scaled decorrelation per millisecond), corresponding to 90% specificity for local ablation prediction. Controlled HIFU thermal ablation experiments were compared with uncontrolled experiments employing two, five or nine sonication cycles. Means and standard errors of the lesion width, area and depth, as well as receiver operating characteristic curves testing ablation prediction performance, were computed for each group. Controlled trials exhibited significantly smaller average lesion area, width and treatment time than five-cycle or nine-cycle uncontrolled trials and also had significantly greater prediction capability than two-cycle uncontrolled trials. These results suggest echo decorrelation imaging is an effective approach to real-time HIFU ablation control.

The efficacy of a new high intensity focused ultrasound therapy for locally advanced pancreatic cancer

PURPOSE

To compare the survival benefit and safety of the low power cumulative and traditional high intensity focused ultrasound (HIFU) for locally advanced pancreatic cancer.

METHOD

We retrospectively analyzed 38 patients with locally advanced, inoperable, stage III pancreatic patients received HIFU treatment between January 2008 and April 2014 in the Department of Surgery, the Second Affiliated Hospital, Zhejiang University, School of Medicine. 11 of them received the low power cumulative HIFU treatment, while other 27 received the traditional HIFU treatment. The HIFU device used was the FEP-BY02 (Yuande Biomedical Engineering Co. Ltd, Beijing, China). Serum biochemistry and adverse events were assessed before and after treatment. All the patients were followed up until death. The survival rate and adverse events of two groups were compared.

RESULTS

In 38 patients, the baseline characteristics including gender, age, Karnofsky performance status (KPS) score, tumor location of two groups were generally well balanced (P > 0.05). The median overall survival (OS) for low power cumulative HIFU group was 10.3 months (95% CI, 6.3-14.3 months), which is significantly longer than traditional HIFU group with 6.0 months (95% CI, 5.2-6.8 months) (P = 0.018). In low power cumulative HIFU group, the 6-month and 12-month survival rates were higher than traditional group, 100% v.s 44.4%, 11.1% v.s 36.4%, respectively. The adverse events in both groups include abdominal pain, fever, C-reactive protein (CRP) elevated. The incidence was lower in low power cumulative HIFU group, however, without statistical significance.

CONCLUSION

The low power cumulative HIFU treatment showed a statistical significance in survival benefit with better safety profile compared to the traditional HIFU treatment in patients with locally advanced pancreatic cancer.

Materials Chemistry of Nanoultrasonic Biomedicine

As a special cross-disciplinary research frontier, nanoultrasonic biomedicine refers to the design and synthesis of nanomaterials to solve some critical issues of ultrasound (US)-based biomedicine. The concept of nanoultrasonic biomedicine can also overcome the drawbacks of traditional microbubbles and promote the generation of novel US-based contrast agents or synergistic agents for US theranostics. Here, we discuss the recent developments of material chemistry in advancing the nanoultrasonic biomedicine for diverse US-based bio-applications. We initially introduce the design principles of novel nanoplatforms for serving the nanoultrasonic biomedicine, from the viewpoint of synthetic material chemistry. Based on these principles and diverse US-based bio-application backgrounds, the representative proof-of-concept paradigms on this topic are clarified in detail, including nanodroplet vaporization for intelligent/responsive US imaging, multifunctional nano-contrast agents for US-based multi-modality imaging, activatable synergistic agents for US-based therapy, US-triggered on-demand drug releasing, US-enhanced gene transfection, US-based synergistic therapy on combating the cancer and potential toxicity issue of screening various nanosystems suitable for nanoultrasonic biomedicine. It is highly expected that this novel nanoultrasonic biomedicine and corresponding high performance in US imaging and therapy can significantly promote the generation of new sub-discipline of US-based biomedicine by rationally integrating material chemistry and theranostic nanomedicine with clinical US-based biomedicine.

Visualization and quantitation of fetal movements by real-time three-dimensional ultrasound with live xPlane imaging in the first trimester of pregnancy

Aim

To prove whether real-time three-dimensional (3D) ultrasound with live xPlane imaging is better in observing fetal movements than standard ultrasound imaging.

Methods

50 healthy women with singleton pregnancies (22-43 years old) at 11 to 14 weeks of gestation underwent real-time 3D ultrasound examination with live xPlane imaging from July 2014 to February 2015. The incidence and frequency of 10 fetal movement patterns in 10 minutes were evaluated, including general movements (GMs), isolated arm movements, isolated leg movements, hiccup, stretching, breathing, startle, jaw opening, isolated head retroflexion, and isolated head anteflexion. The correlation between gestational age and frequency of each fetal movement pattern was analyzed.

Results

GM had the highest incidence (100%), followed by startle (84%) and isolated arm movements (68%). Their median frequency was 5 (IQR 3-6), 5 (IQR 1.75-11.5), and 1 (IQR 0-2), respectively. GM (Z = 5.875, P < 0.001) and startle (Z = 5.302, P < 0.001) had significantly higher frequency than isolated arm movements. The other 7 fetal movement patterns had much lower incidence and frequency. The frequency of GM was positively correlated with gestational age (r = 0.360, P = 0.010).

Conclusion

Real-time 3D ultrasound with live x Plane imaging was shown to be a feasible tool for observing fetal movements.

Modern Palliative Treatments for Metastatic Bone Disease: Awareness of Advantages, Disadvantages, and Guidance

BACKGROUND

Metastatic disease is the most common malignancy of the bone. Prostate, breast, lung, kidney, and thyroid cancer account for 80% of skeletal metastases. Bone metastases are associated with significant skeletal morbidity including severe bone pain, pathologic fractures, spinal cord or nerve roots compression, and malignant hypercalcemia. These events compromise greatly the quality of life of the patients. The treatment of cancer patients with bone metastases is mostly aimed at palliation.

OBJECTIVE

This article aims to present these palliative treatments for the patients with bone metastases, summarize the clinical applications, and review the techniques and results.

METHODS

It gives an extensive overview of the possibilities of palliation in patients with metastatic cancer to the bone.

RESULTS AND DISCUSSION

Currently, modern treatments are available for the palliative management of patients with metastatic bone disease. These include modern radiation therapy, chemotherapy, embolization, electrochemotherapy, radiofrequency ablation, and high-intensity focused ultrasound. As such it is of interest for all physicians with no experience with these developments to make palliative procedures safer and more reliable.

A novel transcutaneous, non-focused ultrasound energy delivering device is able to induce subcutaneous adipose tissue destruction in an animal model

BACKGROUND AND OBJECTIVES

The understanding that adipocytes are greatly influenced by thermal changes combined with the advancement of non-invasive ultrasound technologies have led to the application of ultrasound as an energy source to induce thermal fat destruction. While application of high intensity focused, ultrasound energy have been widely explored, there is far less information regarding the effects of non-focused ultrasound on adipose tissue. The purpose of this study was to characterize the effects of a novel transcutaneous, multi-elements, non-focused ultrasound energy regimen in an animal model, as a proof-of-concept of its potential to treat non-invasive subcutaneous benign tumors.

MATERIALS AND METHODS

The non-invasive transcutaneous ultrasound system prototype (LUMENIS, Ltd., Yoqneam, Israel) was applied to thermally induce adipocytes' death. During treatment, the ultrasound energy was transmitted into the subcutaneous adipose tissue (SAT) of 12 domestic adult female pigs. Two modes of operation (long and short), which differ in both the acoustic energy applied to the tissue and in their time durations (i.e., differ in their power settings), were used in this study. Efficacy and safety assessments included: Temperature measurement of skin and subcutaneous adipose tissue (SAT) visual inspection and ultrasound imaging of the thermally affected areas, histopathological assessment of tissue samples using hematoxylin & eosin, and Masson's trichrome stains and in situ cell death detection kit for apoptosis assessment.

RESULTS

The long and short treatment modes led to a 13.2°C and 17.8°C rise from baseline, respectively, in the SAT, whereas skin surface temperature was practically unaffected. Visual, ultrasonographic, and histopathological evaluation of the treated area showed SAT ablation. No treatment-related changes were observed in the epidermis, dermis subcutaneous muscle and nerves, or in livers and kidneys of treated animals. Additionally, no significant changes from baseline in blood- and urine-borne analytes were detected post-treatment.

CONCLUSIONS

The novel transcutaneous, multi-elements, non-focused ultrasound energy regimen used in this study, proved effective in non-invasively ablating SAT in an animal model. The usage of low energy settings such as in the current study might reduce unwanted side effects related to high energy application. Lasers Surg. Med. 49:110-121, 2017. © 2016 Wiley Periodicals, Inc.

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

Improved Human Bone Marrow Mesenchymal Stem Cell Osteogenesis in 3D Bioprinted Tissue Scaffolds with Low Intensity Pulsed Ultrasound Stimulation

3D printing and ultrasound techniques are showing great promise in the evolution of human musculoskeletal tissue repair and regeneration medicine. The uniqueness of the present study was to combine low intensity pulsed ultrasound (LIPUS) and advanced 3D printing techniques to synergistically improve growth and osteogenic differentiation of human mesenchymal stem cells (MSC). Specifically, polyethylene glycol diacrylate bioinks containing cell adhesive Arginine-Glycine-Aspartic acid-Serene (RGDS) peptide and/or nanocrystalline hydroxyapatite (nHA) were used to fabricate 3D scaffolds with different geometric patterns via novel table-top stereolithography 3D printer. The resultant scaffolds provide a highly porous and interconnected 3D environment to support cell proliferation. Scaffolds with small square pores were determined to be the optimal geometric pattern for MSC attachment and growth. The optimal LIPUS working parameters were determined to be 1.5 MHz, 20% duty cycle with 150 mW/cm(2) intensity. Results demonstrated that RGDS peptide and nHA containing 3D printed scaffolds under LIPUS treatment can greatly promote MSC proliferation, alkaline phosphatase activity, calcium deposition and total protein content. These results illustrate the effectiveness of the combination of LIPUS and biomimetic 3D printing scaffolds as a valuable combinatorial tool for improved MSC function, thus make them promising for future clinical and various regenerative medicine application.

High intensity focused ultrasound (HIFU) applied to hepato-bilio-pancreatic and the digestive system-current state of the art and future perspectives

BACKGROUND

High intensity focused ultrasound (HIFU) is emerging as a valid minimally-invasive image-guided treatment of malignancies. We aimed to review to current state of the art of HIFU therapy applied to the digestive system and discuss some promising avenues of the technology.

METHODS

Pertinent studies were identified through PubMed and Embase search engines using the following keywords, combined in different ways: HIFU, esophagus, stomach, liver, pancreas, gallbladder, colon, rectum, and cancer. Experimental proof of the concept of endoluminal HIFU mucosa/submucosa ablation using a custom-made transducer has been obtained in vivo in the porcine model.

RESULTS

Forty-four studies reported on the clinical use of HIFU to treat liver lesions, while 19 series were found on HIFU treatment of pancreatic cancers and four studies included patients suffering from both liver and pancreatic cancers, reporting on a total of 1,682 and 823 cases for liver and pancreas, respectively. Only very limited comparative prospective studies have been reported.

CONCLUSIONS

Digestive system clinical applications of HIFU are limited to pancreatic and liver cancer. It is safe and well tolerated. The exact place in the hepatocellular carcinoma (HCC) management algorithm remains to be defined. HIFU seems to add clear survival advantages over trans arterial chemo embolization (TACE) alone and similar results when compared to radio frequency (RF). For pancreatic cancer, HIFU achieves consistent cancer-related pain relief. Further research is warranted to improve targeting accuracy and efficacy monitoring. Furthermore, additional work is required to transfer this technology on appealing treatments such as endoscopic HIFU-based therapies.

High-Intensity Focused Ultrasound (HIFU) for Specific Therapeutic Treatments: A Literature Review

A literature review is provided concerning the scientific studies that have been published involving high-intensity focused ultrasound (HIFU) as a therapeutic treatment for tumors of the prostate, uterus, and brain. This is a revival of earlier work that now focuses on targeted therapy with sonography, but the studies that have been conducted vary in their level of evidence and translation to clinical practice. The review arranges the published studies by levels of evidence and provides a meta-analysis of the potential for using HIFU to treat prostate cancer, fibroids, and glioblastomas. Human studies are needed that provide clear levels of frequency, intensity, temperature, and treatment patterns. The bioeffects of sonography play a huge role in the destruction of these tumors as well as the potential to cause collateral damage in the surrounding healthy tissue. The hope is that with continued research, a fusion of technology with HIFU can provide patients with a noninvasive, nonionizing therapy for these lesions.

Chest wall hernia induced by high intensity focused ultrasound treatment of unresectable massive hepatocellular carcinoma: A case report

In the present study, a case of unresectable massive hepatocellular carcinoma (HCC) treated with high intensity focused ultrasound (HIFU) alone is reported. Although the treatment induced chest wall hernia, its efficacy in treating the HCC was demonstrated. The medical records of a patient with an unresectable massive tumor that was effectively treated with serial HIFU ablation were retrospectively studied. Chest wall hernia was detected as a complication of the HIFU treatment, which has not been reported thus far in the literature. The patient has survived for 44 months since the first diagnosis in September 2010. Treatment resulted in partial remission of the tumor, pain relief, decreased levels of alpha-fetoprotein and chest wall hernia, as a complication. Therefore, HIFU may be an effective approach for the treatment of unresectable HCC, although it may occasionally cause complications.

Frequency considerations for deep ablation with high-intensity focused ultrasound: A simulation study

PURPOSE

The objective of this study was to explore frequency considerations for large-volume, deep thermal ablations with focused ultrasound. Though focal patterns, focal steering rate, and the size of focal clusters have all been explored in this context, frequency studies have generally explored shallower depths and hyperthermia applications. This study examines both treatment efficiency and near-field heating rate as functions of frequency and depth.

METHODS

Flat, 150 mm transducer arrays were simulated to operate at frequencies of 250, 500, 750, 1000, 1250, and 1500 kHz. Each array had λ2 interelement spacing yielding arrays of 2000-70 000 piston-shaped elements arranged in concentric rings. Depths of 50, 100, and 150 mm were explored, with attenuation (α) values of 2.5-10 (Np/m)/MHz. Ultrasound propagation was simulated with the Rayleigh-Sommerfeld integral over a volume of homogeneous simulated tissue. Absorbed power density was determined from the acoustic pressure which, in turn, was modeled with the Pennes bioheat transfer equation. Using this knowledge of temperature over time, thermal dose function of Sapareto and Dewey was used to model the resulting bioeffect of each simulated sonication. Initially, single foci at each depth, frequency, and α were examined with either fixed peak temperatures or fixed powers. Based on the size of the resulting, single foci lesions, larger compound sonications were designed with foci packed together in multiple layers and rings. For each depth, focal patterns were chosen to produce a similar total ablated volume for each frequency. These compound sonications were performed with a fixed peak temperature at each focus. The resulting energy efficiency (volume ablated per acoustic energy applied), near-field heating rate (temperature increase in the anterior third of the simulation space per unit volume ablated), and near- and far-field margins were assessed.

RESULTS

Lesions of comparable volume were created with different frequencies at different depths. The results reflect the interconnected nature of frequency as it effects focal size (decreasing with frequency), peak pressure (generally increasing with frequency), and attenuation (also increasing with frequency). The ablation efficiency was the highest for α = 5 (Np/m)/MHz at a frequency of 750 kHz at each depth. For α = 10 (Np/m)/MHz, efficiency was the highest at 750 kHz for a depth of 50 mm, and 500 kHz at depths of 100 and 150 mm. At all sonication depths, near-field heating was minimized with lower frequencies of 250 and 500 kHz.

CONCLUSIONS

Large-volume ablations are most efficient at frequencies of 500-750 kHz at depths of 100-150 mm. When one considers that near-field heat accumulation tends to be the rate limiting factor in large-volume ablations like uterine fibroid surgery, the results show that frequencies as low as 500 kHz are favored for their ability to reduce heating in the near-field.

Influence of ultrasonic scattering in the calculation of thermal dose in ex-vivo bovine muscular tissues

This study explores the effect of ultrasound scattering on the temperature increase in phantoms and in samples of ex-vivo biological tissue through the calculation of the thermal dose (TD). Phantoms with different weight percentages of graphite powder (0-1%w/w, different scattering mean free paths, ℓS) and ex-vivo bovine muscle tissue were isonified by therapeutic ultrasound (1 MHz). The TD values were calculated from the first 4 min of experimental temperature curves obtained at several depths and were compared with those acquired from the numerical solution of the bio-heat transfer equation (simulated with 1 MHz and 0.5-2.0 W cm(-2)). The temperature curves suggested that scattering had an important role because the temperature increments were found to be higher for higher percentages of graphite powder (lower ℓS). For example, at a 30-mm depth and a 4-min therapeutic ultrasound application (0.5 W cm(-2)), the TDs (in equivalent minutes at 43 °C) were 7.2, 17.8, and 58.3 for the phantom with ℓS of 4.35, 3.85, and 3.03 mm, respectively. In tissue, the inclusion of only absorption or full attenuation in the bio-heat transfer equation (BHTE) heat source term of the simulation leads to under- or overestimation of the TD, respectively, as compared to the TD calculated from experimental data. The experiments with phantoms (with different scatterer concentrations) and ex-vivo samples show that the high values of TD were caused by the increase of energy absorption due to the lengthening of the propagation path caused by the changing in the propagation regime.

A review of high intensity focused ultrasound in relation to the treatment of renal tumours and other malignancies

For 60 years, high-intensity focused ultrasound (HIFU) has been the subject of interest for medical research. HIFU causes tissue necrosis in a very well defined area, at a variable distance from the transducer, through heating or cavitation. Over the past two decades, the use of high-intensity focused ultrasound has been investigated in many clinical settings. This review summarises recent advances made in the field of renal cancer in particular, and gives an overview on the use of the extracorporeal machines in the treatment of other malignant tumours.