High-intensity Ultrasound Energy Research Articles

Graphene Synthesis by Ultrasound Energy-Assisted Exfoliation of Graphite in Various Solvents

The liquid-phase exfoliation (LPE) method has been gaining increasing interest by academic and industrial researchers due to its simplicity, low cost, and scalability. High-intensity ultrasound energy was exploited to transform graphite to graphene in the solvents of dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), and perchloric acid (PA) without adding any surfactants or ionic liquids. The crystal structure, number of layers, particle size, and morphology of the synthesized graphene samples were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), ultraviolet visible (UV–vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). XRD and AFM analyses indicated that G-DMSO and G-DMF have few layers while G-PA has multilayers. The layer numbers of G-DMSO, G-DMF, and G-PA were determined as 9, 10, and 21, respectively. By DLS analysis, the particle sizes, polydispersity index (PDI), and zeta potential of graphene samples were estimated in a few micrometers. TEM analyses showed that G-DMSO and G-DMF possess sheet-like fewer layers and also, G-PA has wrinkled and unordered multilayers.

High-intensity ultrasound-assisted recovery of cinnamyl alcohol glycosides from Rhodiola rosea roots: Effect of probe diameter on the ultrasound energy performance for the extraction of bioactive compounds

High-intensity ultrasound (HIUS) energy performance was evaluated using different probe diameters (10 and 20mm) and specific energies (0.5, 1.0, 3.0, and 5.0kJ/g) to recover rosavin and rosin from Rhodiola rosea roots. Also, intensified HIUS process conditions (5, 10, 15, and 20kJ/g) assisted by a cold bath were studied. HIUS energy performance depended on probe diameter at the same nominal power. The larger diameter probe was more energy-efficient, however, the smaller diameter had more ultrasonic intensity (W/cm2). The diameters evaluated did not influence the extraction yields, however, the increase of the HIUS specific energy from 0.5 to 5.0kJ/g increased phenolic compounds content, antioxidant activities, and rosavin and rosin yields. The HIUS process intensification confirmed that the main extraction mechanism was diffusion and the role of the ultrasound was to increase the diffusion coefficients by increasing the turbulence in the liquid medium due to acoustic cavitation.

High-intensity ultrasound energy density: How different modes of application influence the quality parameters of a dairy beverage.

This study evaluated the influence of the high-intensity ultrasound (HIUS) technology on the quality parameters of a model dairy beverage (chocolate whey beverage), operating under the same energy density (5000J/mL), but applied at different ways. Two processes were performed varying nominal power and processing time: HIUS-A (160W and 937s), and HIUS-B (720W and 208s). Our objective was to understand how different modes of application of the same HIUS energy density could influence the microstructure, droplet size distribution, zeta potential, phase separation kinetic, color parameters and mineral profile of the chocolate whey beverage. The results demonstrated that the different modes of application of the same HIUS energy density directly influenced the final quality of the product, resulting in whey beverages with distinct physical and microstructural characteristics. The HIUS-B processing was characterized as a thermal processing, since the final processing temperature reached 71°C, while the HIUS-A processing was a non-thermal process, reaching a final temperature of 34°C. Moreover, HIUS-B process greatly reduced the droplet size and increased the lightness value in relation to the HIUS-A processing. Both treatments resulted in whey beverages with similar phase separation kinetics and were more stable than the untreated sample. The HIUS processes did not modify the mineral content profile. Overall, the study emphasizes the versatility of the HIUS technology, highlighting that the processing must not be based only on the applied energy density, since different powers and processing times produce dairy beverages with distinct characteristics.

Clove essential oil emulsion-filled cellulose nanofiber hydrogel produced by high-intensity ultrasound technology for tissue engineering applications.

High-intensity ultrasound (HIUS) was used to produce emulsion-filled cellulose nanofiber (CNF) hydrogel using clove essential oil (0.1, 0.5 and 1.0 wt%) as dispersed phase towards tissue engineering applications. The novel encapsulating systems obtained using HIUS specific energy at the levels of 0.10, 0.17, and 0.24 kJ/g were characterized by oil entrapment efficiency, microstructure, water retention value, color parameters, and viscoelastic properties. Freeze-dried emulsion-filled CNF hydrogels were characterized by porosity and swelling capacity. In addition, human gingival fibroblast cell cytocompatibility tests were performed to evaluate their potential applications as tissue engineering scaffold. The clove essential oil content strongly affected the oil entrapment efficiency, water retention value, color difference and whiteness of the prepared emulsion-filled CNF hydrogel. And, the HIUS energy only affected the yellowness of the emulsion-filled CNF hydrogel. Via HIUS processing, the CNF hydrogel successfully acted as a continuous phase in the emulsion-filled gel system with maximum oil entrapment efficiency of 34% when 0.5 wt% clove essential oil was added to the system. The encapsulating systems had predominantly gel-like property with maximum elastic modulus of 411 Pa. Furthermore, the emulsion-filled CNF hydrogels with the addition of clove essential oil up to 0.5 wt% indicated good cell viability rates (74-101%) to human gingival fibroblast cells. The newly developed clove essential oil emulsion-filled CNF hydrogel shows desirable cytocompatibility characteristics and can be considered as an alternative scaffold for tissue engineering applications.

Six-Month Angiographic and Clinical Outcomes of Therapeutic Ultrasound Pretreatment Associated With Plain Balloon Angioplasty for Below-the-Knee Lesions in Patients With Critical Limb Ischemia: A Prospective, Single-Center Pilot Study

Purpose: To evaluate the safety and efficacy of low-frequency, high-intensity ultrasound energy delivered via a new dedicated ultrasound catheter followed by conventional balloon angioplasty to treat calcified infrapopliteal lesions. Materials and Methods: A prospective, nonrandomized, single-center pilot study enrolled 12 patients (mean age 72.2±5.3 years; 8 men) with critical limb ischemia (9 Rutherford category 5 and 3 category 6) between January and November 2017. Of the 19 target lesions, 11 had severe calcification. Patients were treated with the Kapani ultrasound system before conventional balloon dilation. Primary safety endpoints included 30-day death, major target limb amputation, and target vessel acute occlusion. The main efficacy outcome was primary patency at 6 months, defined as freedom from both clinically-driven target lesion revascularization (TLR) and angiographically-defined restenosis (>50% lumen reduction). Results: Technical success (<30% residual stenosis) was achieved in all lesions without complications or stent implantation. Ultrasound energy was delivered over a mean 185.2±67.3 seconds followed by low-pressure dilation (mean 6.1±1.9 atm). Angiography confirmed primary patency at 6 months in 18 (95%) of 19 lesions. No death, TLR, or amputation was reported in follow-up. Complete ulcer healing was observed in all 12 patients at 6 months. Conclusion: This pilot trial with a small number of patients suggests that low-frequency, high-intensity ultrasound energy delivery followed by plain balloon angioplasty is a safe approach to treat infrapopliteal atherosclerotic lesions. Angiographically-documented results at 6 months indicate a potential for this combined therapy in the treatment of CLI patients with calcified BTK lesions. Further studies on a larger randomized cohort are needed to confirm these positive clinical outcomes.

Transurethral MR-HIFU for the treatment of localized prostate cancer

Transurethral MR-HIFU involves the delivery of high-intensity ultrasound energy for targeted coagulation of prostate tissue under real-time MRI temperature control.

Development of a new control strategy for 3D MRI‐controlled interstitial ultrasound cancer therapy

MRI-controlled interstitial ultrasound therapy is being developed as a minimally invasive, image-guided treatment for localized cancers. The method uses an interstitial multielement ultrasound applicator to deliver high-intensity ultrasound energy to tissue in order to achieve thermal coagulation in a target volume. A new temperature feedback control algorithm incorporating a proportional-integral controller is introduced to tackle a multiple-input single-output control problem arising in MRI-controlled interstitial ultrasound cancer therapy. The inputs to the controller block are the frequency, rotation rate, and applied power of an interstitial applicator and the output is the boundary temperature during treatment. Multiplanar magnetic resonance (MR) thermometry is acquired continuously during heating and used in the feedback control algorithm to achieve spatial control over treatment. The method has been evaluated for prostate cancer treatment as an initial clinical application. Spatial treatment accuracy of a few millimeters is demonstrated in both simulations and experiments with the new controller. The spatial treatment accuracy of the new algorithm is shown to be equivalent or slightly improved over the existing approach implemented for this technology; however, the implementation of the new algorithm is much simpler, and does not involve time-intensive tuning of gain constants. The study demonstrates the potential advantages of a new automatic temperature control system adapted to image guided interstitial ultrasound therapy.

Novel High-Intensity Focused Ultrasound Clamp—Potential Adjunct for Laparoscopic Partial Nephrectomy

Partial nephrectomy (PN) can be technically challenging, especially if performed in a minimally invasive manner. Although ultrasound technology has been shown to have therapeutic capabilities, including tissue ablation and hemostasis, it has not gained clinical use in the PN setting. The purpose of this study is to evaluate the ability of a high-intensity ultrasound clamp to create an ablation plane in the kidney providing hemostasis that could potentially aid in laparoscopic PN. A new instrument was created using a laparoscopic Padron endoscopic exposing retractor. Ultrasound elements were engineered on both sides of the retractor to administer high-intensity ultrasound energy between the two sides of the clamp. This high-intensity focused ultrasound (HIFU) clamp was placed 2 to 2.5 cm from the upper and lower poles of 10 porcine kidneys to evaluate its effectiveness at different levels and duration of energy delivery. PN transection was performed through the distal portion of the clamped margin. Kidneys postintervention and after PN were evaluated and blood loss estimated by weighing gauze placed at the defect. Histologic analysis was performed with hematoxylin and eosin and nicotinamide adenine dinucleotide staining to evaluate for tissue viability and thermal spread. Gross parenchymal changes were seen with obvious demarcation between treated and untreated tissue. Increased ultrasound exposure time (10 vs 5 and 2 min), even at lower power settings, was more effective in causing destruction and necrosis of tissue. Transmural ablation was achieved in three of four renal units after 10 minutes of exposure with significantly less blood loss (<2 g vs 30-100 g). Nonviable tissue was confirmed histologically. There was minimal thermal spread outside the clamped margin (1.2-3.2 mm). In this preliminary porcine evaluation, a novel HIFU clamp induced hemostasis and created an ablation plane in the kidney. This technology could serve as a useful adjunct to laparoscopic PN in the future and potentially obviate the need for renal hilar clamping.

1782 THE USE OF MRI-GUIDED TRANSURETHRAL ULTRASOUND THERAPY FOR THE TREATMENT OF LOCALIZED PROSTATE CANCER: A PHASE I STUDY

You have accessJournal of UrologyProstate Cancer: Localized1 Apr 20111782 THE USE OF MRI-GUIDED TRANSURETHRAL ULTRASOUND THERAPY FOR THE TREATMENT OF LOCALIZED PROSTATE CANCER: A PHASE I STUDY Alexandra Colquhoun, Harry Foster, Linda Sugar, Masoom Haider, Laurence Klotz, Michael Bronskill, and Rajiv Chopra Alexandra ColquhounAlexandra Colquhoun Toronto, Canada More articles by this author , Harry FosterHarry Foster Toronto, Canada More articles by this author , Linda SugarLinda Sugar Toronto, Canada More articles by this author , Masoom HaiderMasoom Haider Toronto, Canada More articles by this author , Laurence KlotzLaurence Klotz Toronto, Canada More articles by this author , Michael BronskillMichael Bronskill Toronto, Canada More articles by this author , and Rajiv ChopraRajiv Chopra Toronto, Canada More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2011.02.2132AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Minimally-invasive treatments for localized prostate cancer, that offer good local control over disease with a low side-effect profile, would have a major impact in improving prostate cancer management. MRI-guided transurethral ultrasound therapy is a candidate technology in which planar high-intensity ultrasound energy is delivered to the prostate gland, via a transurethrally inserted device to generate a precise region of thermal coagulation. Previous studies in canines have demonstrated the feasibility of using active MR temperature feedback to control spatial heating to a specified target region. This phase I study was designed to evaluate the safety and feasibility of this technique in humans. METHODS MRI-guided transurethral ultrasound therapy was administered, using a combination of sedation and spinal anesthesia, to a pre-determined region of the prostate of men diagnosed with localized prostate cancer (pT1c–pT2a). Subjects underwent immediate radical prostatectomy, and the pattern of thermal damage measured on histology was compared with imaging predictions. High-intensity ultrasound energy was delivered to a 180° sector in the prostate and spatial temperature maps were obtained every five seconds. The temperature measured at the boundary of the target region during treatment was used by the treatment system to adjust the power and rotation rate. RESULTS Eight patients, median age 60 (range 49–70), were successfully treated. Baseline biopsy Gleason scores were 3+3 (n=4) and 3+4 (n=4) and the median pre-biopsy PSA, 4.9 (range 2.7–13.1). The transurethral device was inserted without difficulty and spinal anesthesia and sedation effectively eliminated patient discomfort and motion during the 2 hour procedure. Precise transducer positioning was achieved under image guidance, and successful device rotation was achieved within the prostate. MR temperature measurements within the prostate were achieved with a spatial resolution of 2mm and a temperature uncertainty of 1°C every 5 seconds, using a conventional pelvic surface coil array. Temperature measurements were stable, and not affected by motion or breathing. A continuous pattern of heating was delivered over the target region, with a targeting accuracy of 1.0+/−1.5mm. There were no reported complications. CONCLUSIONS MRI-guided transurethral ultrasound therapy is safe and capable of generating a precise region of thermal damage within the prostate gland under active MR temperature feedback. © 2011 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 185Issue 4SApril 2011Page: e715-e716 Advertisement Copyright & Permissions© 2011 by American Urological Association Education and Research, Inc.MetricsAuthor Information Alexandra Colquhoun Toronto, Canada More articles by this author Harry Foster Toronto, Canada More articles by this author Linda Sugar Toronto, Canada More articles by this author Masoom Haider Toronto, Canada More articles by this author Laurence Klotz Toronto, Canada More articles by this author Michael Bronskill Toronto, Canada More articles by this author Rajiv Chopra Toronto, Canada More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

84 THE USE OF MRI-GUIDED TRANSURETHRAL ULTRASOUND THERAPY FOR THE TREATMENT OF LOCALISED PROSTATE CANCER: A PHASE I STUDY

Minimally-invasive treatments for localized prostate cancer, that offer good local control over disease with a low side-effect profile, would have a major impact in improving the management of this disease. MRI-guided transurethral ultrasound therapy is a candidate technology in which planar high-intensity ultrasound energy is delivered to the prostate gland, via a transurethrally inserted device to generate a precise region of thermal coagulation (figure 1). Previous studies in gel models and canines have demonstrated the feasibility of using active MR temperature feedback to control spatial heating to a specified target region. This phase I study was designed to evaluate the safety and feasibility of this technique in humans.

MRI-controlled transurethral ultrasound therapy for localised prostate cancer

Minimally invasive treatments for localised prostate cancer are being developed with the aim of achieving effective disease control with low morbidity. High-temperature thermal therapy aimed at producing irreversible thermal coagulation of the prostate gland is attractive because of the rapid onset of thermal injury, and the immediate visualisation of tissue response using medical imaging. High-intensity ultrasound therapy has been shown to be an effective means of achieving thermal coagulation of prostate tissue using minimally invasive devices inserted into the rectum, urethra, or directly into the gland itself. The focus of this review is to describe the work done in our group on the development of MRI-controlled transurethral ultrasound therapy. This technology utilises high intensity ultrasound energy delivered from a transurethral device to achieve thermal coagulation of prostate tissue. Control over the spatial pattern of thermal damage is achieved through closed-loop temperature feedback using quantitative MR thermometry during treatment. The technology, temperature feedback algorithms, and results from numerical modelling, along with experimental results obtained in animal and human studies are described. Our experience suggests that this form of treatment is technically feasible, and compatible with existing MR imaging systems. Temperature feedback control algorithms using MR thermometry can achieve spatial treatment accuracy of a few millimetres in vivo. Patient-specific simulations predict that surrounding tissues can be spared from thermal damage if appropriate measures are taken into account during treatment planning. Recent human experience has been encouraging and motivates further evaluation of this technology as a potential treatment for localised prostate cancer.

MRI-guided Transurethral Ultrasound Therapy of the Prostate Gland Using Real-time Thermal Mapping: Initial Studies

To confirm the correlation between planning and thermal injury of the prostate as determined by magnetic resonance imaging (MRI) and histology in canine and humans treated with transurethral ultrasound. Canine studies: 2 sets of in vivo studies were performed under general anesthesia in 1.5 T clinical MRI. Nine dogs were treated using single transducer; 8 dogs were treated using urethral applicator with multiple transducers. Rectal cooling was maintained. After initial imaging, a target boundary was selected and high-intensity ultrasound energy delivered. The spatial temperature distribution was measured continuously every 5 seconds with MR thermometry using the proton-resonant frequency shift method. The goal was to achieve 55 °C at the target boundary. After treatment, the prostate was harvested and fixed with adjoining tissue, including rectum. Temperature maps, anatomical images, and histologic sections were registered to each other and compared. Human studies: To date, 5 patients with localized prostate cancer have been treated immediately before radical prostatectomy. Approximately 30% of the gland volume was targeted. A continuous pattern of thermal coagulation was successfully achieved within the target region, with an average spatial precision of 1-2 mm. Radical prostatectomy was routine, with an uncomplicated postoperative course in all patients. The correlation between anatomical, thermal, and histologic images was ≤3 mm. Treatment time was <30 minutes. No thermal damage to rectal tissue was observed. Thermal ablation within the prescribed target of the prostate has been successfully demonstrated in canine studies. The treatment is also feasible in humans.

Sci-Sat AM(2): Brachy - 06: Characterization of Dual-Frequency, Multi-Element Heating Applicators for MRI-Guided Transurethral Ultrasound Therapy

MRI-guided transurethral ultrasound therapy is a minimally-invasive treatment for localized prostate cancer that provides local control with a low side-effect profile which would have a major impact in improving disease management. High-intensity ultrasound energy from a device inserted into the prostatic urethra generates an accurate region of thermal coagulation in the gland under MR-temperature control. The purpose of this study was to characterize the acoustic, electrical and spatial properties of multi-element ultrasound transducers designed for MRI-guided transurethral ultrasound therapy. The transducer design is described, along with characterization of the electrical and acoustic properties of the device. Transmission spectrum and power output are shown for a single element illustrating their high acoustic efficiencies and power stability at fundamental and third harmonic frequencies. These results provide insight into the heating characteristics of this ultrasound device and its suitability for treating localized prostate cancer.

V324 HISTOTRIPSY ABLATION OF THE PROSTATE IN A CANINE MODEL

You have accessJournal of UrologyMale Voiding Dysfunction (BPH & Incontinence) & Infection1 Apr 2010V324 HISTOTRIPSY ABLATION OF THE PROSTATE IN A CANINE MODEL Jeffery Wheat, Nicholas Styn, Timothy Hall, Christopher Hempel, J. Brian Fowlkes, Charles Cain, and William Roberts Jeffery WheatJeffery Wheat More articles by this author , Nicholas StynNicholas Styn More articles by this author , Timothy HallTimothy Hall More articles by this author , Christopher HempelChristopher Hempel More articles by this author , J. Brian FowlkesJ. Brian Fowlkes More articles by this author , Charles CainCharles Cain More articles by this author , and William RobertsWilliam Roberts More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.389AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Histotripsy is a non-invasive, non-thermal ultrasound based technology that produces mechanical fractionation of biologic tissues through a process called cavitation. Cavitation occurs when high intensity ultrasound energy is focused to a small point at the geometric focus of a therapeutic ultrasound transducer causing the formation, oscillation and collapse of microbubbles. In this video, we demonstrate the technique of histotripsy and evaluate its safety and efficacy in a chronic canine model. METHODS A total of 18 male canine subjects were treated with histotripsy. The subjects were anesthetized and treatment was delivered to the prostate from an extracorporeal 16-element phased array submerged in a bath of degassed water positioned above the subject's abdomen. Treatment was monitored in real time with transrectal diagnostic ultrasound and was deemed adequate when a hypoechoic region was identified within the targeted region. Complete blood count, serum chemistry, and validated veterinary pain scores were obtained before and after treatment. The prostate, bladder and rectum were harvested up to 28 days following treatment, fixed in formalin and stained for histologic analysis. RESULTS Histotripsy was well tolerated in all subjects without treatment related complications. Following treatment, there were transient elevations in white blood cell count and liver enzymes, both of which normalized by the time of harvest. Pain scores normalized within 24 hours of catheter removal. On histologic examination, a large cavity without residual debris was seen within the prostate corresponding to the treated region (Figure 1). Four weeks following treatment, the lining of the treated cavity was re-urothelialized (Figure 2). CONCLUSIONS Histotripsy is a promising non-invasive technology for ablation of biologic tissues. This treatment appears to be safe and effective for debulking the prostate in a canine model. Further studies are underway to translate this technology to human applications. Ann Arbor, MI© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e128-e129 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Jeffery Wheat More articles by this author Nicholas Styn More articles by this author Timothy Hall More articles by this author Christopher Hempel More articles by this author J. Brian Fowlkes More articles by this author Charles Cain More articles by this author William Roberts More articles by this author Expand All Advertisement Advertisement PDF DownloadLoading ...

Analysis of the spatial and temporal accuracy of heating in the prostate gland using transurethral ultrasound therapy and active MR temperature feedback

A new MRI-guided therapy is being developed as a minimally invasive treatment for localized prostate cancer utilizing high-intensity ultrasound energy to generate a precise region of thermal coagulation within the prostate gland. The purpose of this study was to evaluate in vivo the capability to produce a spatial heating pattern in the prostate that accurately matched the shape of a target region using transurethral ultrasound heating and active MR temperature feedback. Experiments were performed in a canine model (n = 9) in a 1.5 T MR imager using a prototype device comprising a single planar transducer operated under rotational control. The spatial temperature distribution, measured every 5 s with MR thermometry, was used to adjust the acoustic power and rotation rate in order to achieve a temperature of 55 °C along the outer boundary of the target region. The results demonstrated the capability to produce accurate spatial heating patterns within the prostate gland. An average temperature of 56.2 ± 0.6 °C was measured along the outer boundary of the target region across all experiments in this study. The average spatial error between the target boundary and the 55 °C isotherm was 0.8 ± 0.7 mm (−0.2 to 3.2 mm), and the overall treatment time was ⩽20 min for all experiments. Excellent spatial agreement was observed between the temperature information acquired with MRI and the pattern of thermal damage measured on H&E-stained tissue sections. This study demonstrates the benefit of adaptive energy delivery using active MR temperature feedback, and an excellent capability to treat precise regions within the prostate gland with this technology.

MRI‐compatible transurethral ultrasound system for the treatment of localized prostate cancer using rotational control

Magnetic resonance imaging (MRI)-guided transurethral ultrasound therapy is a potential minimally invasive treatment for localized prostate cancer offering precise targeting of tissue within the gland, short treatment times, and the capability to quantify the spatial heating pattern delivered during therapy. A significant challenge in MRI-guided ultrasound therapy is the design and construction of MRI-compatible equipment capable of operation in a closed-bore MR imager. We describe a prototype system developed for MRI-guided transurethral ultrasound therapy and characterize the performance of the different components including the heating applicator design, rotational motor, and radio frequency electronics. The ultrasound heating applicator described in this study incorporates a planar transducer and is capable of producing high intensity ultrasound energy in a localized region of tissue. Results demonstrated that the heating applicator exhibits excellent MRI-compatibility, enabling precise MR temperature measurements to be acquired as close as 6 mm from the device. Simultaneous imaging and rotational motion was also possible during treatment using a motor based on piezoelectric actuators. Heating experiments performed in both phantoms and in a canine model with the prototype system verified the capability to perform simultaneous MR imaging and therapy delivery with this system. Real-time control over therapy using MR temperature measurements acquired during heating can be implemented to achieve precise patterns of thermal damage within the prostate gland. The technical feasibility of using the system developed in this study for MRI-guided transurethral ultrasound therapy in a closed-bore MR imager has been demonstrated.

Protective effect of free-radical scavengers on corneal endothelial damage in phacoemulsification

To examine the role of the water-soluble antioxidants glutathione and ascorbic acid in the irrigating solution on corneal endothelial cells following exposure to high-intensity ultrasound energy. Goldschleger Eye Research Institute, Sheba Medical Center, Tel-Aviv University, Tel Aviv, Israel. Thirty-two rabbit eyes were subjected to prolonged exposure to the phacoemulsification device in the anterior chamber. The eyes were divided into 4 groups that differed only in the composition of the irrigating solution applied to the eyes: balanced salt solution (BSS) BSS Plus BSS containing additional soluble components including glutathione, BSS with 10(-3) M of oxidized glutathione (GSSG), and BSS with 10(-2) M of ascorbic acid. Specular microscopy was performed preoperatively and 1 week after surgery. The BSS group exhibited the highest endothelial cell loss (19.3%), followed by the BSS Plus group (10.6%), the GSSG group (5.2%), and the ascorbic acid group (0.9%). An overall difference was found between the groups (F = 11.046, P<.0001), and all groups demonstrated a statistically significant difference from the control BSS group (P<.02, P = .001, and P<.0001, respectively). Damage to the cornea is largely due to the free radicals generated by high-intensity ultrasound energy during phacoemulsification. Adding the antioxidants ascorbic acid and GSSG to the irrigation solution significantly reduced the endothelial corneal cell damage. Ascorbic acid in the concentration of 10(-2) M had the highest protective effect; thus, it should be evaluated for clinical use.

2029: Standardization of medical ultrasound instrumentation applying high-intensity ultrasound energy—the cavitation index and cavitation biosafety index

2029: Standardization of medical ultrasound instrumentation applying high-intensity ultrasound energy—the cavitation index and cavitation biosafety index

Controlled high efficiency lesion formation using high intensity ultrasound

An ultrasound system used for both imaging and delivery high intensity ultrasound energy therapy to treatment sites and a method for treating tumors and other undesired tissue within a patient's body with an ultrasound device. The ultrasound device has an ultrasound transducer array disposed on a distal end of an elongate, relatively thin shaft. In one form of the invention, the transducer array is disposed within a liquid-filled elastomeric material that more effectively couples ultrasound energy into the tumor, that is directly contacted with the device. Using the device in a continuous wave mode, a necrotic zone of tissue having a desired size and shape (e.g., a necrotic volume selected to interrupt a blood supply to a tumor) can be created by controlling at least one of the f-number, duration, intensity, and direction of the ultrasound energy administered. This method speeds the therapy and avoids continuously pausing to enable intervening normal tissue to cool.

Is there evidence for excessive free radical production in vivo during ultrasound-assisted liposuction?

The surgical technique of ultrasound-assisted liposuction has become a standard procedure for the treatment of lipodystrophy. However, little is known about the impact of this therapy on fatty tissue on the molecular level. There are concerns about possible adverse effects related to the high-intensity ultrasound energy, because in vitro studies have shown a substantial generation of free radicals. In this study, the authors investigated whether ultrasound waves can create an excessive free radical production in vivo by measuring lipid peroxidation products in the form of malondialdehyde equivalents. For this purpose, the thiobarbituric acid-reactive substances (TBARS) assay was chosen. In this test, malondialdehyde, a major product of lipid peroxidation, reacts with thiobarbituric acid to produce a pink adduct that can be measured spectrophotometrically. The authors determined oxidation products in 28 aspirates of 17 treated patients before ultrasound-assisted liposuction (0 minutes) to establish a baseline concentration and at 2, 5, and 10 minutes after the treatment was begun. Median malondialdehyde concentration of the control group (conventional liposuction, 0 minutes) was 3.40 nmol of malondialdehyde per gram of adipose tissue. Median concentrations after 2, 5, and 10 minutes of ultrasound-assisted liposuction were 7.45 (n = 28), 8.84 (n = 21), and 4.07 (n = 8) nmol malondialdehyde per gram adipose tissue, respectively. The differences were not statistically significant. The data suggest that there is no excessive formation of lipid oxidation products in response to free radicals. The antioxidative capacity of adipose tissue does not seem to be overwhelmed by the standard application regimen of ultrasound-assisted liposuction.