Analysis of clinical effect of high-intensity focused ultrasound on liver cancer

Suppressing the HIFU interference in ultrasound guiding images with a diffusion-based deep learning model

BACKGROUND AND OBJECTIVES

In ultrasound guided high-intensity focused ultrasound (HIFU) surgery, it is necessary to transmit sound waves at different frequencies simultaneously using two transducers: one for the HIFU therapy and another for the ultrasound imaging guidance. In this specific setting, real-time monitoring of non-invasive surgery is challenging due to severe contamination of the ultrasound guiding images by strong acoustic interference from the HIFU sonication.

METHODS

This paper proposed the use of a deep learning (DL) solution, specifically a diffusion implicit model, to suppress the HIFU interference. We considered the images contaminated with HIFU interference as low-resolution images, and those free from interference as high-resolution. While suppressing HIFU interference using the diffusion implicit (HIFU-Diff) model, the task was transformed into generating a high-resolution image through a series of forward diffusion steps and reverse sampling. A series of ex-vivo and in-vivo experiments, conducted under various parameters, were designed to validate the performance of the proposed network.

RESULTS

Quantitative evaluation and statistical analysis demonstrated that the HIFU-Diff network achieved superior performance in reconstructing interference-free images under a variety of ex-vivo and in-vivo conditions, compared to the most commonly used notch filtering and the recent 1D FUS-Net deep learning network. The HIFU-Diff maintains high performance with 'unseen' datasets from separate experiments, and its superiority is more pronounced under strong HIFU interferences and in complex in-vivo situations. Furthermore, the reconstructed interference-free images can also be used for quantitative attenuation imaging, indicating that the network preserves acoustic characteristics of the ultrasound images.

CONCLUSIONS

With the proposed technique, HIFU therapy and the ultrasound imaging can be conducted simultaneously, allowing for real-time monitoring of the treatment process. This capability could significantly enhance the safety and efficacy of the non-invasive treatment across various clinical applications. To the best of our knowledge, this is the first diffusion-based model developed for HIFU interference suppression.

Advances in Image-Guided Ablation Therapies for Solid Tumors

Image-guided solid tumor ablation methods have significantly advanced in their capability to target primary and metastatic tumors. These techniques involve noninvasive or percutaneous insertion of applicators to induce thermal, electrochemical, or mechanical stress on malignant tissue to cause tissue destruction and apoptosis of the tumor margins. Ablation offers substantially lower risks compared to traditional methods. Benefits include shorter recovery periods, reduced bleeding, and greater preservation of organ parenchyma compared to surgical intervention. Due to the reduced morbidity and mortality, image-guided tumor ablation offers new opportunities for treatment in cancer patients who are not candidates for resection. Currently, image-guided ablation techniques are utilized for treating primary and metastatic tumors in various organs with both curative and palliative intent, including the liver, pancreas, kidneys, thyroid, parathyroid, prostate, lung, breast, bone, and soft tissue. The invention of new equipment and techniques is expanding the criteria of eligible patients for therapy, as now larger and more high-risk tumors near critical structures can be ablated. This article provides an overview of the different imaging modalities, noninvasive, and percutaneous ablation techniques available and discusses their applications and associated complications across various organs.

Suppressing HIFU interference in ultrasound images using 1D U-Net-based neural networks

Objective.One big challenge with high-intensity focused ultrasound (HIFU) is that the intense acoustic interference generated by HIFU irradiation overwhelms the B-mode monitoring images, compromising monitoring effectiveness. This study aims to overcome this problem using a one-dimensional (1D) deep convolutional neural network.Approach. U-Net-based networks have been proven to be effective in image reconstruction and denoising, and the two-dimensional (2D) U-Net has already been investigated for suppressing HIFU interference in ultrasound monitoring images. In this study, we propose that the one-dimensional (1D) convolution in U-Net-based networks is more suitable for removing HIFU artifacts and can better recover the contaminated B-mode images compared to 2D convolution.Ex vivoandinvivoHIFU experiments were performed on a clinically equivalent ultrasound-guided HIFU platform to collect image data, and the 1D convolution in U-Net, Attention U-Net, U-Net++, and FUS-Net was applied to verify our proposal.Main results.All 1D U-Net-based networks were more effective in suppressing HIFU interference than their 2D counterparts, with over 30% improvement in terms of structural similarity (SSIM) to the uncontaminated B-mode images. Additionally, 1D U-Nets trained usingex vivodatasets demonstrated better generalization performance ininvivoexperiments.Significance.These findings indicate that the utilization of 1D convolution in U-Net-based networks offers great potential in addressing the challenges of monitoring in ultrasound-guided HIFU systems.

Dense speed-of-sound shift imaging for ultrasonic thermometry

Objective. Develop a dense algorithm for calculating the speed-of-sound shift between consecutive acoustic acquisitions as a noninvasive means to evaluating temperature change during thermal ablation.Methods. An algorithm for dense speed-of-sound shift imaging (DSI) was developed to simultaneously incorporate information from the entire field of view using a combination of dense optical flow and inverse problem regularization, thus speeding up the calculation and introducing spatial agreement between pixels natively. Thermal ablation monitoring consisted of two main steps: pixel shift tracking using Farneback optical flow, and mathematical modeling of the relationship between the pixel displacement and temperature change as an inverse problem to find the speed-of-sound shift. A calibration constant translates from speed-of-sound shift to temperature change. The method performance was tested inex vivosamples and compared to standard thermal strain imaging (TSI) methods.Main results. Thermal ablation at a frequency of 2 MHz was applied to an agarose phantom that created a speed-of-sound shift measured by an L12-5 imaging transducer. A focal spot was reconstructed by solving the inverse problem. Next, a thermocouple measured the temperature rise during thermal ablation ofex vivochicken breast to calibrate the setup. Temperature changes between 3 °C and 15 °C was measured with high thermometry precision of less than 2 °C error for temperature changes as low as 8 °C. The DSI method outperformed standard TSI in both spatial coherence and runtime in high-intensity focused ultrasound-induced hyperthermia.Significance. Dense ultrasonic speed-of-sound shift imaging can successfully monitor the speed-of-sound shift introduced by thermal ablation. This technique is faster and more robust than current methods, and therefore can be used as a noninvasive, real time and cost-effective thermometry method, with high clinical applicability.

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.

Controlled Hyperthermia With High-Intensity Focused Ultrasound and Ultrasound Contrast Agent Microbubbles in Porcine Liver

OBJECTIVE

The objective of this work was to study microbubble-enhanced temperature elevation with high-intensity focused ultrasound (HIFU) at different acoustic pressures and under image guidance. The microbubbles were administered with either local or vascular injections (that mimic systemic injections) in perfused and non-perfused ex vivo porcine liver under ultrasound image guidance.

METHODS

Porcine liver was insonified for 30 s with a single-element HIFU transducer (0.9 MHz, 0.413 ms, 82% duty cycle, focal pressures of 0.6-3.5 MPa). Contrast microbubbles were injected either locally or through the vasculature. A needle thermocouple at the focus measured temperature elevation. Diagnostic ultrasound (Philips iU22, C5-1 probe) guided placement of the thermocouple and delivery of microbubbles and monitored the procedure in real time.

RESULTS

At lower acoustic pressures (0.6 and 1.2 MPa) in non-perfused liver, inertial cavitation of the injected microbubbles led to greater temperatures at the focus compared with HIFU-only treatments. At higher pressures (2.4 and 3.5 MPa) native inertial cavitation in the tissue (without injecting microbubbles) resulted in temperature elevations similar to those after injecting microbubbles. The heated area was larger when using microbubbles at all pressures. In the presence of perfusion, only local injections provided a sufficiently high concentration of microbubbles necessary for significant temperature enhancement.

CONCLUSION

Local injections of microbubbles provide a higher concentration of microbubbles in a smaller area, avoiding acoustic shadowing, and can lead to higher temperature elevation at lower pressures and increase the size of the heated area at all pressures.

Evaluation of Ultrasonic Attenuation in Primary and Secondary Human Liver Tumors and Its Potential Effect on High-Intensity Focused Ultrasound Treatment

Primary and secondary liver tumors are completely different diseases but are usually treated similarly using high-intensity focused ultrasound (HIFU). However, the acoustic parameters of these tissues are not well documented. In this study, attenuation coefficients were evaluated in fresh primary (N = 8) and secondary (N = 13) human liver tumor samples recovered by hepatectomy. The average attenuation coefficients of the primary and secondary liver tumors were 0.10 ± 0.03 and 0.20 ± 0.04 Np/cm/MHz, respectively. The average attenuation coefficients of the liver tissue surrounding the primary and secondary tumors were 0.16 ± 0.07 and 0.07 ± 0.02 Np/cm/MHz, respectively. Numerical simulations performed using these values revealed that completely different HIFU ablation patterns were created in primary and secondary liver tumors using the same exposure parameters. The dimensions of a typical HIFU lesion were two times larger in secondary liver tumors than in primary tumors. HIFU treatment parameters should be set properly according to the acoustic properties of the diseased liver tissue.

Robotic system for magnetic resonance guided focused ultrasound ablation of abdominal cancer

BACKGROUND

A prototype robotic system that uses magnetic resonance guided focused ultrasound (MRgFUS) technology is presented. It features three degrees of freedom (DOF) and is intended for thermal ablation of abdominal cancer.

METHODS

The device is equipped with three identical transducers being offset between them, thus focussing at different depths in tissue. The efficacy and safety of the system in ablating rabbit liver and kidney was assessed, both in laboratory and magnetic resonance imaging (MRI) conditions.

RESULTS

Despite these organs' challenging location, in situ coagulative necrosis of a tissue area was achieved. Heating of abdominal organs in rabbit was successfully monitored with MR thermometry.

CONCLUSIONS

The MRgFUS system was proven successful in creating lesions in the abdominal area of rabbits. The outcomes of the study are promising for future translation of the technology to the clinic.

Carbon nanotube-mediated high intensity focused ultrasound

High intensity focused ultrasound (HIFU) is emerging as a novel therapeutic technique for cancer treatment through a hyperthermal mechanism using ultrasound. However, collateral thermal damages to healthy tissue and skin burns due to the use of high levels of ultrasonic energy during HIFU treatment remain major challenges to clinical application. The main objective of the current study is to evaluate the potential of carbon nanotubes (CNTs) as effective absorption-enhancing agents for HIFU to mediate the heating process at low ultrasonic power levels, and consequently upgrade hyperthermal therapeutic effects of HIFU. An experimental study using in vitro tissue phantoms was conducted to assess the effects of CNTs on HIFU’s heating mechanism. Detailed information was extracted from the experiments for thermal analysis, including rate of absorbed energy density and temperature rise profile at the focal region. Parametric studies were carried out, revealing the effects of ultrasound parameters (ultrasonic power and driving frequency) on the performance of CNTs in various concentrations. The results indicated that CNTs significantly enhanced the thermal effect of HIFU by elevating energy absorption rate and consequential temperature rise. Moreover, it was demonstrated that an increase in ultrasonic power and driving frequency could lead to a better performance of CNTs during HIFU ablation procedures; the effects of CNTs could be further enhanced by increasing their volume concentration inside the medium.

A Computational Study on Temperature Variations in MRgFUS Treatments Using PRF Thermometry Techniques and Optical Probes

Structural and metabolic imaging are fundamental for diagnosis, treatment and follow-up in oncology. Beyond the well-established diagnostic imaging applications, ultrasounds are currently emerging in the clinical practice as a noninvasive technology for therapy. Indeed, the sound waves can be used to increase the temperature inside the target solid tumors, leading to apoptosis or necrosis of neoplastic tissues. The Magnetic resonance-guided focused ultrasound surgery (MRgFUS) technology represents a valid application of this ultrasound property, mainly used in oncology and neurology. In this paper; patient safety during MRgFUS treatments was investigated by a series of experiments in a tissue-mimicking phantom and performing ex vivo skin samples, to promptly identify unwanted temperature rises. The acquired MR images, used to evaluate the temperature in the treated areas, were analyzed to compare classical proton resonance frequency (PRF) shift techniques and referenceless thermometry methods to accurately assess the temperature variations. We exploited radial basis function (RBF) neural networks for referenceless thermometry and compared the results against interferometric optical fiber measurements. The experimental measurements were obtained using a set of interferometric optical fibers aimed at quantifying temperature variations directly in the sonication areas. The temperature increases during the treatment were not accurately detected by MRI-based referenceless thermometry methods, and more sensitive measurement systems, such as optical fibers, would be required. In-depth studies about these aspects are needed to monitor temperature and improve safety during MRgFUS treatments.

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.

High-intensity focused ultrasound ablation as a treatment for benign thyroid diseases: the present and future

High-intensity focused ultrasound (HIFU) is a promising ablation technique for benign thyroid nodules. Current evidence has found good short- to medium-term outcomes, similar to those of better-established ablation techniques such as radiofrequency and laser ablation. The fact that it does not require insertion of a needle into the target makes HIFU a truly non-invasive treatment. Although it is not without risks, its low risk profile makes it an attractive alternative to surgery. There is much room for future development, starting from expanding the current indications to enhancing energy delivery. Relapsed Graves disease and papillary microcarcinoma are diseases that can benefit from HIFU treatment. Its role in the mediation of immune responses and synergistic effects with immunotherapy are promising in the fight against metastatic cancers.

Fabrication and Characterization of Single-Aperture 3.5-MHz BNT-Based Ultrasonic Transducer for Therapeutic Application

This paper discusses the fabrication and characterization of 3.5-MHz single-element transducers for therapeutic applications in which the active elements are made of hard lead-free BNT-based and hard commercial PZT (PZT-841) piezoceramics. Composition of (BiNa_0.88K_0.08Li_0.04)_0.5(Ti_0.985Mn_0.015)O₃ (BNKLT88-1.5Mn) was used to develop lead-free piezoelectric ceramic. Mn-doped samples exhibited high mechanical quality factor ( ) of 970, thickness coupling coefficient ( ) of 0.48, a dielectric constant ( ) of 310 (at 1 kHz), depolarization temperature ( ) of 200 °C, and coercive field ( ) of 52.5 kV/cm. Two different unfocused single-element transducers using BNKLT88-1.5Mn and PZT-841 with the same center frequency of 3.5 MHz and similar aperture size of 10.7 and 10.5 mm were fabricated. Pulse-echo response, acoustic frequency spectrum, acoustic pressure field, and acoustic intensity field of transducers were characterized. The BNT-based transducer shows linear response up to the peak-to-peak voltage of 105 V in which the maximum rarefactional acoustic pressure of 1.1 MPa, and acoustic intensity of 43 W/cm² were achieved. Natural focal point of this transducer was at 60 mm from the surface of the transducer.

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.

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.

Nanoscale theranostics for physical stimulus-responsive cancer therapies

Physical stimulus-responsive therapies often employing multifunctional theranostic agents responsive to external physical stimuli such as light, magnetic field, ultra-sound, radiofrequency, X-ray, etc., have been widely explored as novel cancer therapy strategies, showing encouraging results in many pre-clinical animal experiments. Unlike conventional cancer chemotherapy which often accompanies with severe toxic side effects, physical stimulus-responsive agents usually are non-toxic by themselves and would destruct cancer cells only under specific external stimuli, and thus could offer greatly reduced toxicity and enhanced treatment specificity. In addition, physical stimulus-responsive therapies can also be combined with other traditional therapeutics to achieve synergistic anti-tumor effects via a variety of mechanisms. In this review, we will summarize the latest progress in the development of physical stimulus-responsive therapies, and discuss the important roles of nanoscale theranostic agents involved in those non-conventional therapeutic strategies.

Removing atherosclerotic plaque created using high cholesterol diet in rabbit using ultrasound

Background

The aim of the proposed study was to conduct a feasibility study using a flat rectangular (3 × 10 mm²) transducer operating at 5 MHz for removing atherosclerotic plaque in an in vivo model. The proposed method can be used in the future for treating atherosclerotic plaques in humans.

Methods and results

The plaque in the rabbits was created using high cholesterol diet for 4 months. The amount of plaque removed was studied as a function of intensity, with a fixed pulse repetition frequency (PRF), and duty factor (DF).

Conclusions

The amount of plaque removed is directly related to the acoustic intensity. It was found that the presence of bubbles accelerates the removal of plaque. In order to ensure that pure mechanical mode ultrasound was used, the intensity used does not produce temperatures that exceed 1°C.

Review of MRI positioning devices for guiding focused ultrasound systems

BACKGROUND

This article contains a review of positioning devices that are currently used in the area of magnetic resonance imaging (MRI) guided focused ultrasound surgery (MRgFUS).

METHODS

The paper includes an extensive review of literature published since the first prototype system was invented in 1991.

RESULTS

The technology has grown into a fast developing area with application to any organ accessible to ultrasound. The initial design operated using hydraulic principles, while the latest technology incorporates piezoelectric motors. Although, in the beginning there were fears regarding MRI safety, during recent years, the deployment of MR-safe positioning devices in FUS has become routine. Many of these positioning devices are now undergoing testing in clinical trials.

CONCLUSION

Existing MRgFUS systems have been utilized mostly in oncology (fibroids, brain, liver, kidney, bone, pancreas, eye, thyroid, and prostate). It is anticipated that, in the near future, there will be a positioning device for every organ that is accessible by focused ultrasound.

MR-guided focused ultrasound surgery, present and future

MR-guided focused ultrasound surgery (MRgFUS) is a quickly developing technology with potential applications across a spectrum of indications traditionally within the domain of radiation oncology. Especially for applications where focal treatment is the preferred technique (for example, radiosurgery), MRgFUS has the potential to be a disruptive technology that could shift traditional patterns of care. While currently cleared in the United States for the noninvasive treatment of uterine fibroids and bone metastases, a wide range of clinical trials are currently underway, and the number of publications describing advances in MRgFUS is increasing. However, for MRgFUS to make the transition from a research curiosity to a clinical standard of care, a variety of challenges, technical, financial, clinical, and practical, must be overcome. This installment of the Vision 20∕20 series examines the current status of MRgFUS, focusing on the hurdles the technology faces before it can cross over from a research technique to a standard fixture in the clinic. It then reviews current and near-term technical developments which may overcome these hurdles and allow MRgFUS to break through into clinical practice.

Ex Vivo characterization of canine liver tissue viscoelasticity after high-intensity focused ultrasound ablation

The potential of elasticity imaging to detect high-intensity focused ultrasound (HIFU) lesions on the basis of their distinct biomechanical properties is promising. However, information on the quantitative mechanical properties of the tissue and the optimal intensity at which to determine the best contrast parameters is scarce. In this study, fresh canine livers were ablated using combinations of ISPTA intensities of 5.55, 7.16 and 9.07 kW/cm(2) and durations of 10 and 30 s ex vivo, resulting in six groups of ablated tissues. Biopsy samples were then interrogated using dynamic shear mechanical testing within the range of 0.1-10 Hz to characterize the tissue's post-ablation viscoelastic properties. All mechanical parameters were found to be frequency dependent. Compared with unablated cases, all six groups of ablated tissues had statistically significant higher complex shear modulus and shear viscosity. However, among the ablated groups, both complex shear modulus and shear viscosity were found to monotonically increase in groups 1-4 (5.55 kW/cm(2) for 10 s, 7.16 kW/cm(2) for 10 s, 9.07 kW/cm(2) for 10 s, and 5.55 kW/cm(2) for 30 s, respectively), but to decrease in groups 5 and 6 (7.16 kW/cm(2) for 30 s, and 9.07 kW/cm(2) for 30 s, respectively). For groups 5 and 6, the temperature was expected to exceed the boiling point, and therefore, the decreased stiffening could be due to the compromised integrity of the tissue microstructure. Future studies will entail estimation tissue mechanical properties in vivo and perform real-time monitoring of tissue alterations during ablation.

High-intensity focused ultrasound treatment for patients with unresectable pancreatic cancer

BACKGROUND

High-intensity focused ultrasound (HIFU) is a non-invasive method of solid tissue ablation therapy. However, only a few studies have reported the effect of HIFU for unresectable pancreatic cancer. This study aimed to evaluate the clinical benefits, survival time and complications associated with the use of HIFU ablation in patients with unresectable pancreatic cancer.

METHODS

Twenty-five patients with unresectable pancreatic cancer were enrolled in our study. All patients received HIFU therapy for tumors at least once. The therapeutic effects of HIFU was evaluated in terms of Karnofsky performance status (KPS) scores, pain relief, serum CA19-9, and imaging by B-US and CT before and after the therapy. We also recorded median overall survival time and complications caused by the treatment.

RESULTS

In the 25 patients, KPS scores were above 60, and increased KPS was observed in 23 patients after treatment. Pain relief occurred in 23 patients. Serum CA19-9 levels were significantly reduced one month after HIFU treatment and became negative in 5 patients. B-US revealed enhanced tumor echogenicity in 13 patients and decreased tumor blood supply in 9. Tumor necrosis was confirmed by CT in 8 patients one month after HIFU treatment. The median overall survival time was 10 months, and the 1-year survival rate was 42%. No severe complications were observed after HIFU treatment.

CONCLUSION

HIFU can effectively relieve pain, increase KPS, decrease tumor growth and prolong the survival time of patients with unresectable pancreatic cancer.

The destructive effects of high-intensity focused ultrasound on hydatid cysts enhanced by ultrasound contrast agent and superabsorbent polymer alone or in combination

Cystic echinococcosis, caused by the metacestode stage of Echincoccus granulosus, remains endemic in many regions around the world. The present work evaluated whether or not a superabsorbent polymer (SAP) and ultrasound contrast agent (UCA) alone or in combination could enhance damage efficacy of high-intensity focused ultrasound (HIFU) on hydatid cysts in vitro. HIFU of 100 W acoustic power, with the aid of 0.1 ml UCA and 0.1 g SAP alone or in combination, was used to ablate hydatid cysts in vitro. The comparison of ultrasound image for each layer of hydatid cyst before and after HIFU ablation was made immediately, and the protoscolices of the cysts were stained by eosin exclusion assay, and the structures of protoscolices were observed by light microscopy. To understand the destructive effects of HIFU, the pathological changes in cyst walls of hydatid cyst ablated with HIFU were examined. The results demonstrated that HIFU had some lethal effect on hydatid cysts: echo enhancement of ultrasound image, increase of mortality rate of protoscolices, serious structural damage of protoscolices, and complete destruction or even disappearance of laminated layer and germinal layer was observed in the group of HIFU combined with UCA and SAP alone or in combination. It was found that the destructive effect of HIFU aided with a combination of UCA and SAP to hydatid cysts was more effective than that of HIFU just aided with UCA or SAP alone. These results suggested that UCA and SAP might be used as a HIFU enhancing agent to improve the efficacy of HIFU ablation to hydatid cysts, which could be a possible therapeutic option for cystic echinococcosis.

Low-pressure pulsed focused ultrasound with microbubbles promotes an anticancer immunological response

Background

High-intensity focused-ultrasound (HIFU) has been successfully employed for thermal ablation of tumors in clinical settings. Continuous- or pulsed-mode HIFU may also induce a host antitumor immune response, mainly through expansion of antigen-presenting cells in response to increased cellular debris and through increased macrophage activation/infiltration. Here we demonstrated that another form of focused ultrasound delivery, using low-pressure, pulsed-mode exposure in the presence of microbubbles (MBs), may also trigger an antitumor immunological response and inhibit tumor growth.

Methods

A total of 280 tumor-bearing animals were subjected to sonographically-guided FUS. Implanted tumors were exposed to low-pressure FUS (0.6 to 1.4 MPa) with MBs to increase the permeability of tumor microvasculature.

Results

Tumor progression was suppressed by both 0.6 and 1.4-MPa MB-enhanced FUS exposures. We observed a transient increase in infiltration of non-T regulatory (non-Treg) tumor infiltrating lymphocytes (TILs) and continual infiltration of CD8+ cytotoxic T-lymphocytes (CTL). The ratio of CD8+/Treg increased significantly and tumor growth was inhibited.

Conclusions

Our findings suggest that low-pressure FUS exposure with MBs may constitute a useful tool for triggering an anticancer immune response, for potential cancer immunotherapy.

High-intensity focused ultrasound tumor ablation activates autologous tumor-specific cytotoxic T lymphocytes

Previous studies have shown that high-intensity focused ultrasound (HIFU) ablation can enhance host antitumor immune response, though the mechanism is still unknown. In the present study, we investigated whether HIFU ablation could activate tumor-specific T lymphocytes and then induce antitumor cellular immunity. We studied 70 C57BL/6J mice bearing the H(22) tumor; they were randomly divided into a HIFU group and a sham-HIFU group. Of the mice, 35 in the HIFU group underwent HIFU ablation of the H(22) hepatic tumor, and the remaining 35 received a sham-HIFU procedure. In addition, 35 female, naïve syngeneic C57BL/6J mice were used as controls. All mice were sacrificed 14 days after HIFU, and the spleens were harvested. The function of T lymphocytes was determined. As a valuable tool for detecting and characterizing peptide-specific cells, the frequency of MHC class I tetramer/CD8-positive cells was quantified, which could help to determine the response and number of T lymphocytes. The therapeutic effect of the HIFU-activated lymphocytes on tumor-bearing mice was investigated after adoptive transfer of the lymphocytes. The results showed that compared to sham-HIFU and control groups, HIFU ablation significantly increased the cytotoxicity of cytotoxic T lymphocytes (p < 0.05), with a significant increase of IFN-γ and TNF-α secretion (p < 0.001). The frequency of the MHC class I tetramer/CD8-positive cells was significantly higher in the HIFU group (p < 0.05). A stronger inhibition of tumor progression and higher survival rates were observed to be significant after adoptive immunotherapy in the HIFU group as compared to the sham-HIFU and control groups (p < 0.01). It is concluded that HIFU ablation could activate tumor-specific T lymphocytes, thus inducing antitumor cellular immune responses in tumor-bearing mice.

High-intensity focused ultrasound treatment of liver tumours: post-treatment MRI correlates well with intra-operative estimates of treatment volume

OBJECTIVES

To assess the safety and feasibility of high-intensity focused ultrasound (HIFU) ablation of liver tumours and to determine whether post-operative MRI correlates with intra-operative imaging.

METHODS

31 patients were recruited into two ethically approved clinical trials (median age 64; mean BMI 26 kg m(-2)). Patients with liver tumours (primary or metastatic) underwent a single HIFU treatment monitored using intra-operative B-mode ultrasound. Follow-up consisted of radiology and histology (surgical trial) or radiology alone (radiology trial). Radiological follow-up was digital subtraction contrast-enhanced MRI.

RESULTS

Treatment according to protocol was possible in 30 of 31 patients. One treatment was abandoned because of equipment failure. Transient pain and superficial skin burns were seen in 81% (25/31) and 39% (12/31) of patients, respectively. One moderate skin burn occurred. One patient died prior to radiological follow-up. Radiological evidence of ablation was seen in 93% (27/29) of patients. Ablation accuracy was good in 89% (24/27) of patients. In three patients the zone of ablation lay ≤2 mm outside the tumour. The median cross-sectional area (CSA) of the zone of ablation was 5.0 and 5.1 cm(2) using intra-operative and post-operative imaging, respectively. The mean MRI:B-mode CSA ratio was 1.57 [95% confidence interval (CI)=0.57-2.71]. There was positive correlation between MRI and B-mode CSA (Spearman's r=0.48; 95% CI 0.11-0.73; p=0.011) and the slope of linear regression was significantly non-zero (1.23; 95% CI=0.68-1.77; p<0.0001).

CONCLUSIONS

HIFU ablation of liver tumours is safe and feasible. HIFU treatment is accurate, and intra-operative assessment of treatment provides an accurate measure of the zone of ablation and correlates well with MRI follow-up.

Transcatheter arterial chemoembolization in combination with high-intensity focused ultrasound for unresectable hepatocellular carcinoma: a systematic review and meta-analysis of the chinese literature

To evaluate the therapeutic effects of transcatheter arterial chemoembolization (TACE) in combination with high-intensity focused ultrasound (HIFU) for unresectable hepatocellular carcinoma (UHCC), we performed a systematic review and meta-analysis by searching the database. In nine controlled trials with a total of 736 patients, the effect of TACE plus HIFU (group A) was compared with TACE alone (group B) in treating UHCC. Outcomes mainly included tumor response and survival. Pooled odds ratios (ORs) and 95% confidence intervals (CIs) were calculated for each relationship from raw study data using the fixed-effect model or the random effect model. We found that group A significantly improved the tumor response and 0.5-, 1-, 2-, and 3-year survival of patients. In conclusion, combined therapy was more therapeutically beneficial. However, considering the strength of the evidence, additional randomized controlled trials are needed before combined therapy can be recommended routinely.

High-intensity focused ultrasound for hepatocellular carcinoma: a single-center experience

OBJECTIVE

This study aims to evaluate the outcome of patients with hepatocellular carcinoma (HCC) treated by high-intensity focused ultrasound (HIFU) in a single tertiary referral center.

BACKGROUND

HIFU is the latest developed local ablation technique for unresectable HCC. The initial experience on its efficacy is promising, but the survival benefit of patients undergoing HIFU for HCC is poorly defined.

METHODS

From October 2006 to December 2008, 49 patients received HIFU for unresectable HCC. Each patient underwent a single session of HIFU with a curative intent. Treatment efficacy and survival outcome were evaluated. Clinicopathologic factors affecting the primary technique effectiveness and overall survival rates were investigated by univariate analysis.

RESULTS

The median size of the treated tumors was 2.2 cm, ranging from 0.9 to 8 cm. The majority of patients had single tumors (n = 41, 83.6%). Thirty-one patients (63.2%) had artificial right pleural effusion during HIFU treatment to reduce damage to the lung and diaphragm. The hospital mortality rate was 2% (n = 1) and the complication rate was 8.1% (n = 4). The primary technique effectiveness rate was 79.5% (39 of 49 patients). It increased from 66.6% in the initial series to 89.2% in the last 28 patients. Tumor size (≥3.0 cm) was the significant risk factor affecting the complete ablation rate. The 1- and 3-year overall survival rates were 87.7% and 62.4%, respectively. Child-Pugh liver function grading was the significant prognostic factor influencing the overall survival rate.

CONCLUSIONS

HIFU is an effective treatment modality for unresectable HCC with a high technique effectiveness rate and favorable survival outcome.

High intensity focused ultrasound in clinical tumor ablation

Recent advances in high intensity focused ultrasound (HIFU), which was developed in the 1940s as a viable thermal tissue ablation approach, have increased its popularity. In clinics, HIFU has been applied to treat a variety of solid malignant tumors in a well-defined volume, including the pancreas, liver, prostate, breast, uterine fibroids, and soft-tissue sarcomas. In comparison to conventional tumor/cancer treatment modalities, such as open surgery, radio- and chemo-therapy, HIFU has the advantages of non-invasion, non-ionization, and fewer complications after treatment. Over 100 000 cases have been treated throughout the world with great success. The fundamental principles of HIFU ablation are coagulative thermal necrosis due to the absorption of ultrasound energy during transmission in tissue and the induced cavitation damage. This paper reviews the clinical outcomes of HIFU ablation for applicable cancers, and then summarizes the recommendations for a satisfactory HIFU treatment according to clinical experience. In addition, the current challenges in HIFU for engineers and physicians are also included. More recent horizons have broadened the application of HIFU in tumor treatment, such as HIFU-mediated drug delivery, vessel occlusion, and soft tissue erosion (“histotripsy”). In summary, HIFU is likely to play a significant role in the future oncology practice.

Theoretical and experimental study on temperature elevation behind ribs caused by weakly focused ultrasound

Temperature distribution in tissues behind ribs produced by weakly focused ultrasound had been calculated using Pennes bioheat equation and the validity of the theoretical model was experimentally confirmed in vitro using porcine live. We found that the position of the maximum temperature in tissue is strongly influenced by the distance between the transducer and ribs, while the gap between ribs is the determining factor for the maximum achievable temperature. Within the focal length, when the distance between the transducer and ribs increases, the maximum temperature increases and its position shifts away from the transducer. The rib width has little effect on the position of the maximum temperature but affects the achievable peak temperature. Our results provide useful information for treating liver cancers using ultrasound induced hyperthermia.

Focused ultrasound as a local therapy for liver cancer

Conventional surgical treatments of liver cancer are invasive (including minimally invasive) with a high incidence of new metastasis and poor success, even after multiple resections or ablations. These limitations motivated research into new, less invasive solutions for liver cancer treatment.Focused ultrasound surgery (FUS), or high-intensity focused ultrasound, has been recognized as a noninvasive technology for benign and malignant tumor treatment. Previously, FUS was guided with ultrasound that has limited target definition and monitoring capability of the ablation process. Combining magnetic resonance imaging (MRI) with multiple-element phased-array transducers to create MRI-guided focused ultrasound thermal therapy provides more accurate targeting and real-time temperature monitoring. This treatment is hindered by the ribcage that limits the acoustic windows to the liver and the respiratory motion of the liver. New advances in MRI and transducer design will likely resolve these limitations and make MRI-guided FUS a powerful tool in local liver cancer therapy. This article reviews this technology and advances that can expand its use for cancer treatment in general and liver cancer in particular.

High intensity focused ultrasound in the treatment of abdominal and gynaecological diseases

In recent years high intensity focused ultrasound (HIFU) has received increasing interest as a non-invasive modality for the treatment of tumours of solid organs. Surgeons continue their quest to find the optimal technique whereby a diseased organ can be treated with a minimum of damage to the patient, while providing a comprehensive treatment to produce either cure or resolution of symptoms. Two of the areas in which HIFU is beginning to establish itself as a real therapeutic alternative, are in the treatment of abdominal and gynaecological disease. In this paper, we will review the literature available regarding the use of HIFU in the treatment of various organs: liver, kidney, pancreas, bladder, uterus and vulva.

Ablation of high-intensity focused ultrasound assisted with SonoVue on Rabbit VX2 liver tumors: sequential findings with histopathology, immunohistochemistry, and enzyme histochemistry

BACKGROUND

We investigated sequential effects of HIFU ablation combined with contrast agent SonoVue by using histopathology examination, immunohistochemistry, and enzyme histochemistry.

MATERIALS AND METHODS

Forty rabbits with VX2 liver tumors were subjected to HIFU ablation. Before ablation, a bolus injection of 0.2 mL SonoVue was administrated in group II (n = 20), and normal saline solution was injected in group I (n = 20). On day 0, 3, 7, and 14 after ablation, 5 animals in each group were sacrificed. The tissue in ablated zone, transient zone (within 3 mm around ablated area), and surrounding zone (beyond 3 mm around ablated area) were collected. Coagulated volume measurement, hematoxylin-eosin staining, immunohistochemistry of Ki 67, Bcl-2, CD54, and MMP-2 to determine cell proliferation and tissue repair, and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and succinic dehydrogenase (SDH) staining to evaluate tissue viability were performed.

RESULTS

The coagulated volume in group II at each time point was larger than that in group I (P < .05). After day 3, hematoxylin-eosin staining demonstrated necrosis in ablated zones and increasing surrounding fibra bands in group I and group II, while increasing expression of Ki 67, Bcl-2, CD54, and MMP-2 in transient zones was detected using immunohistochemistry in both groups (P > .05). NADPH-d and SDH staining showed dramatic decrease of enzyme activities in ablated zones immediately after ablation, while residual viable tissues in ablated zones of group II were less than those of group I (P < .05).

CONCLUSION

Contrast agent SonoVue enables improvement of HIFU ablation on rabbit VX2 liver tumors.

Magnetic resonance imaging as a technique for assessing noninvasive tissue ablation using high-intensity ultrasound: an experimental study

BACKGROUND AND PURPOSE

As a form of noninvasive extracorporeal application, acoustic energy offers an alternative to nephron-sparing surgery for renal masses smaller than 4 cm. The availability of a reliable tool for monitoring the therapy is a prerequisite for safe and successful high-intensity focused ultrasound (HIFU) application. The aim of this study was to evaluate the morphologic visualization of HIFU lesions using MRI.

MATERIALS AND METHODS

We used the ex vivo model of the isolated perfused porcine kidney. Treatment was performed using an experimental HIFU system. Complex lesions were induced in 10 kidneys. MRI was performed under constant perfusion of the kidneys. To determine the exact lesion size, we performed a fat-saturated, T1-weighted, volumetric interpolated breath-hold MRI sequence. For perfusion imaging, we used a three-dimensional fast low-angle shot sequence. Subsequently, the lesions were evaluated macroscopically. The width of the complex lesions was defined as x, the length as y, and the depth as z.

RESULTS

The MRI scans showed good soft tissue contrast in all sequences. The mean difference for the width of the lesions was 0.2 +/- 1.1 mm; for lesion length and depth, it was 1.7 +/- 1.8 mm and 1.1 +/- 1.3 mm for lesion width, respectively. Statistical evaluation of the x values showed no significant difference between the macroscopic and the MRI data (P = 0.85). The y and z values, however, showed a statistically significant difference (P = 0.071).

CONCLUSION

MRI could be a diagnostic tool for monitoring HIFU. Before this modality can be used under clinical conditions, further technical development is indispensable, especially with respect to reducing the measuring times.

Current role of ultrasound for the management of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a decisive influence on the prognosis of cirrhotic patients. Although α-fetoprotein (AFP) is a known and specific tumor maker for HCC, it is not suitable for the screening and surveillance of HCC because of its poor predictive value and low sensitivity. The use of imaging modalities is essential for the screening, diagnosis and treatment of HCC. Ultrasound (US) plays a major role among them, because it provides real-time and non-invasive observation by a simple and easy technique. In addition, US-guided needle puncture methods are frequently required for the diagnosis and/or treatment process of HCC. The development of digital technology has led to the detection of blood flow by color Doppler US, and the sensitivity for detecting tumor vascularity has shown remarkable improvement with the introduction of microbubble contrast agents. Moreover, near real-time 3-dimensional US images are now available. As for the treatment of HCC, high intensity focused ultrasound (HIFU) was developed as a novel technology that provides a transcutaneous ablation effect without needle puncture. These advancements in the US field have led to rapid progress in HCC management, and continuing advances are expected. This article reviews the current application of US for HCC in clinical practice.

High-intensity focused ultrasound: current potential and oncologic applications

OBJECTIVE

The objective of this article is to introduce the reader to the principles and applications of high-intensity focused ultrasound (HIFU).

CONCLUSION

Although a great deal about HIFU physics is understood, its clinical applications are currently limited, and multiple trials are underway worldwide to determine its efficacy.

Perspectives on transdermal ultrasound mediated drug delivery

The use of needles for multiple injection of drugs, such as insulin for diabetes, can be painful. As a result, prescribed drug noncompliance can result in severe medical complications. Several noninvasive methods exist for transdermal drug delivery. These include chemical mediation using liposomes and chemical enhancers or physical mechanisms such as microneedles, iontophoresis, electroporation, and ultrasound. Ultrasound enhanced transdermal drug delivery offers advantages over traditional drug delivery methods which are often invasive and painful. A broad review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for noninvasive drug administration. From a clinical perspective, few drugs, proteins or peptides have been successfully administered transdermally because of the low skin permeability to these relatively large molecules, although much work is underway to resolve this problem. The proposed mechanism of ultrasound has been suggested to be the result of cavitation, which is discussed along with the bioeffects from therapeutic ultrasound. For low frequencies, potential transducers which can be used for drug delivery are discussed, along with cautions regarding ultrasound safety versus efficacy.

Short and long term efficacy of high intensity focused ultrasound therapy for advanced hepatocellular carcinoma

BACKGROUND

The aim of this study was to investigate the short and long term efficacy of high intensity focused ultrasound therapy (HIFU) in patients with advanced hepatocellular carcinoma (HCC).

METHODS

Patients with surgically unresectable HCC received either HIFU plus supportive treatment (HIFU group, n = 151) or supportive treatment only (control group, n = 30), according to their willingness. Short term efficacy, including improvement in tumor imaging parameters, decrease in serum alpha-fetoprotein (AFP) levels, symptom relief (i.e. Karnofsky Performance Status and numerical rating scales) and response rates, and long term efficacy, including an increase in survival rates and improvement of quality of life (QOL), was monitored.

RESULTS

Tumor imaging parameters, serum AFP levels and symptom scores improved significantly in the HIFU group compared with the control group (all P < 0.05). In the HIFU group, a complete and a partial response were achieved in 28.5% (n = 43) and 60.3% (n = 91) of cases, respectively, while the rates were 0% and 16.7% (n = 5), respectively, in the control group. The overall response rate (88.8%) was significantly greater in the HIFU group (16.7%) than in the control group (P < 0.01). In addition, the 1- and 2-year survival rates were 50.0% and 30.9%, respectively, in the HIFU group, which were significantly greater than those (3.4% and 0%, respectively) in the control group (both P < 0.01). The QOL score was 83.1 +/- 8.0 at 3 months after HIFU, which was significantly greater than the pre-HIFU score (67.7 +/- 5.9) and the score at 3 months after treatment (69.0 +/- 8.5) in the control group (both P < 0.05). No severe complications occurred during and after HIFU.

CONCLUSION

HIFU is an effective and safe ablation therapy with satisfactory short and long term efficacy for patients with advanced HCC.

Developing an interstitial ultrasound applicator for thermal ablation in liver: results of animal experiments

BACKGROUND

In this project, an interstitial ultrasound applicator was developed for the treatment of primary and secondary cancers of the liver. Experiments on animals were used to check the destructive capabilities of this probe within the hepatic parenchyma of the pig in vivo, with a study of the physical parameters of the ultrasound treatment. In parallel, the possibility of visualizing the lesions induced by means of ultrasound imaging was also studied.

MATERIALS AND METHODS

Thirteen pigs were used in this project, which had received the prior approval of the ethics committee of Lyon Veterinary School. Ultrasound lesions were performed by varying the physical parameters of the treatment (acoustic intensity and shot time) with the aim of obtaining larger and larger areas of destruction. An operative device was developed to ensure precision in treatments. Two types of lesions were performed: elementary lesions corresponding to single shots at 40 degrees to 50 degrees rotation intervals, and cylindrical lesions obtained by a continuous rotary deployment of the probe. The effect of hepatic pedicle clamping on the size of ultrasound lesions was studied. The aspect and dimension of the lesions were analyzed by means of operative ultrasound imaging and macroscopic examination. Histological analysis showed the impact of the treatment on the hepatic parenchyma.

RESULTS

This work made it possible to study the elementary ultrasound lesions produced by our probe. Seventy elementary ultrasound lesions were analyzed. Treatments could be performed on all pigs without any difficulty. There were no operative incidents. The ultrasound-induced elementary lesions showed complete necrosis, with lesion length of up to 37 mm obtained without resort to pedicle clamping; this must be considered as a radius of the final lesion obtained over a complete rotary deployment (360 degrees ), then a diameter of 7 cm of thermal ablation can theoretically be obtained. The effect of pedicle clamping was studied and showed improvement of the lesion length. Results of continuous rotary deployment of the probe were encouraging. Operative ultrasound imaging proved to be a simple tool for directing and positioning the applicator in the target zone on the one hand and which, on the other hand, enabled accurate, real-time visualization of the ultrasound lesions. On histological analysis, the ultrasound-induced necrosis was complete and well defined.

CONCLUSION

This work shows that it is feasible to treat cancers of the liver using interstitial ultrasound probe. Thermal damage obtained on the hepatic parenchyma of pigs in vivo is complete and can be monitored using simple diagnostic ultrasound. The ultrasound parameters can be adapted to obtain destruction of variable size.

Recent applications of ultrasound: diagnosis and treatment of hepatocellular carcinoma

Ultrasound (US) has the advantages of real-time observation, simple technique, and a noninvasive procedure compared to other imaging modalities. The recent development of digital technologies has enabled the observation of sonograms with improved signal-to-noise ratio, penetration, and spatial and contrast resolutions. Furthermore, microbubble contrast agents have increased the diagnostic ability of US examination, and the use of three-dimensional sonograms is now not unusual. These advances have furthered the usefulness of US for liver tumors in clinical practice. This article reviews the recent applications of US in the diagnosis and treatment of hepatocellular carcinoma.