Noninvasive creation of an atrial septal defect by histotripsy in a canine model.

BACKGROUND: The primary objective of this study was to develop an image-guided, noninvasive procedure to create or enlarge an atrial septal defect for the treatment of neonates with hypoplastic left heart syndrome and an intact or restrictive atrial septum. Histotripsy is an innovative ultrasonic technique that produces nonthermal, mechanical tissue fractionation through the use of high-intensity ultrasound pulses. This article reports the pilot in vivo study to create an atrial septal defect through the use of extracardiac application of histotripsy in an open-chest canine model. METHODS AND RESULTS: In 10 canines, the atrial septum was exposed to histotripsy by an ultrasound transducer positioned outside the heart. Ultrasound pulses of 6-microsecond duration at a peak negative pressure of 15 MPa and a pulse repetition frequency of 3.3 kHz were generated by a 1-MHz focused transducer. The procedure was guided and monitored by real-time ultrasound imaging. In 9 of 10 canines, an atrial septal defect was produced, and shunting across the atrial septum was visualized. Pathology of the hearts showed atrial septal defects with minimal damage to surrounding tissue. No damage was found on the epicardial surface of the heart or other structures. CONCLUSIONS: Under real-time ultrasound guidance, atrial septal defects were successfully created with extracardiac histotripsy in a live canine model. Although further studies in an intact animal model are needed, these results provide promise of histotripsy becoming a valuable clinical tool.

Thermal effects generated by high-intensity focused ultrasound beams at normal incidence to a bone surface.

Experiments and computations were performed to study factors affecting thermal safety when high-intensity focused ultrasound (HIFU) beams are normally incident (i.e., beam axis normal to the interface) upon a bone/soft-tissue interface. In particular, the temperature rise and thermal dose were determined as a function of separation between the beam focus and the interface. Under conditions representative of clinical HIFU procedures, it was found that the thermal dose at the bone surface can exceed the threshold for necrosis even when the beam focus is more than 4 cm from the bone. Experiments showed that reflection of the HIFU beam from the bone back into the transducer introduced temperature fluctuations of as much as +/-15% and may be an important consideration for safety analyses at sufficiently high acoustic power. The applicability of linear propagation models in predicting thermal dose near the interface was also addressed. Linear models, while underpredicting thermal dose at the focus, provided a conservative (slight overprediction) estimate of thermal dose at the bone surface. Finally, temperature rise due to absorption of shear waves generated by the HIFU beam in the bone was computed. Modeling shear-wave propagation in the thermal analysis showed that the predicted temperature rise off axis was as much as 30% higher when absorption of shear waves is included, indicating that enhanced heating due to shear-wave absorption is potentially important, even for normally incident HIFU beams.

Comparative analyses of cell disruption methods for mitochondrial isolation in high-throughput proteomics study.

One of the most crucial steps in mitochondrial isolation is disruption of intact cells to denude intracellular organelles, but the yield and purity of different disruption protocols have not been well addressed. In the present study, MDCK cells were disrupted by mechanical (sonication and homogenization), physical (repeated freeze/thaw cycles and hypoosmotic burst), and chemical (using Triton X-100, NP-40, or CHAPS) methods. Efficacy of cell disruption was evaluated by trypan blue staining and mitochondria were subsequently isolated by standardized differential centrifugation. The yield of isolation was also determined by measuring protein concentrations, whereas the purity was examined by Janus green B staining, Western blot analyses of markers for mitochondria (COX-4) and other subcellular organelles/locales (i.e., nucleus, cytoplasm, endoplasmic reticulum, and lysosome), transmission electron microscopy, two-dimensional electrophoresis, and Q-TOF MS and/or MS/MS analyses. Our data demonstrated that sonication is the method of choice for disruption of cells prior to mitochondrial isolation for proteome analysis.

Sister chromatid exchanges in human lymphocytes after exposure to diagnostic ultrasound.

The frequency of sister chromatid exchanges increased in freshly isolated human lymphocytes as well as in a continuously growing lymphoblast line by exposure to diagnostic levels of ultrasound for 30 minutes. The results confirm previous findings indicating that ultrasound of diagnostic intensities can affect the DNA of animal cells.

Ultrasound effects.

In a listing of the new foreign associates of the National Academy of Sciences (News and Comment, 17 May, p. 826), the name of Pierre Chambon, Biochemistry, Institut de Chimie Biologique, Faculté de Médecine, Strasbourg, France, was inadvertently omitted.

Description of radiation- and ultrasound-induced cell death by a stochastic process.

Cell survival is a stochastic process with the stochastic component being strongly dependent on the irradiation conditions. This process is described by a stochastic model which allows differentiation between the deterministic and stochastic components of survival. The proposed model is tested for four irradiation experiments (2 with ionizing radiation and 2 with ultrasound) and very good agreement with experimental results is demonstrated. It identifies the higher stochasticity of the cell survival for the temporally varying radiation fields and provides the possibility to compare the stochasticity of survival in different radiation fields.

Skin-traction method prevents the collapse of the internal jugular vein caused by an ultrasound probe in real-time ultrasound-assisted guidance.

PURPOSE: Real-time ultrasound-assisted guidance for catheterization of the internal jugular vein (IJV) is known to be useful, especially for a small-sized vein, which is difficult to catheterize. However, one of the problems with real-time ultrasound-assisted guidance is that the ultrasound probe itself can collapse the vein. We have developed a novel "skintraction method (STM)", in which the puncture point of the skin over the IJV is stretched upwards with several pieces of surgical tape in the cephalad and caudal directions with the aim being to facilitate catheterization of the IJV. We examined whether this method increased the compressive force required to collapse the IJV. METHODS: In ten volunteers, the compressive force required to collapse the right IJV, and the cross-sectional area and anteroposterior and transverse diameters of the IJV were measured with ultrasound imaging in the supine position (SP) with or without the STM or in the Trendelenburg position of 10 degrees head-down (TP) without the STM. RESULTS: The compressive force to required to collapse the vein was increased significantly with the STM, while the crosssectional area and anteroposterior diameter of the vein in the SP with STM were similar to those in the TP without the STM. CONCLUSION: With the STM, not only the cross-sectional area but also the compressive force required to collapse the IJV increased. Thus, the STM may facilitate real-time ultrasoundassisted guidance for catheterization of the IJV by maintaining the cross-sectional area of the vein during the guidance.

Ultrasound targeted microbubble destruction for drug and gene delivery.

BACKGROUND: Gas-filled microbubbles have been used as ultrasound contrast agents for some decades. More recently, such microbubbles have evolved as experimental tools for organ- and tissue-specific drug and gene delivery. When sonified with ultrasound near their resonance frequency, microbubbles oscillate. With higher ultrasound energies, oscillation amplitudes increase, leading to microbubble destruction. This phenomenon can be used to deliver a substance into a target organ, if microbubbles are co-administered loaded with drugs or gene therapy vectors before i.v. injection. OBJECTIVE: This review focuses on different experimental applications of microbubbles as tools for drug and gene delivery. Different organ systems and different classes of bioactive substances that have been used in previous studies will be discussed. METHODS: All the available literature was reviewed to highlight the potential of this non-invasive, organ-specific delivery system. CONCLUSION: Ultrasound targeted microbubble destruction has been used in various organ systems and in tumours to successfully deliver drugs, proteins, gene therapy vectors and gene silencing constructs. Many proof of principle studies have demonstrated its potential as a non-invasive delivery tool. However, too few large animal studies and studies with therapeutic aims have been performed to see a clinical application of this technique in the near future. Nevertheless, there is great hope that preclinical large animal studies will confirm the successful results already obtained in small animals.

Applications of ultrasonic skin permeation in transdermal drug delivery.

Transdermal ultrasound-mediated drug delivery has been studied as a method for needle-less, non-invasive drug administration. Potential obstacles include the stratum corneum, which is not sufficiently passively permeable to allow effective transfer of many medications into the bloodstream without active methods. A general review of the transdermal ultrasound drug delivery literature has shown that this technology offers promising potential for non-invasive drug administration. Included in this review are the reported acoustic parameters used for achieving delivery, along with the known intensities and exposure times. Ultrasound mechanisms are discussed as well as spatial field characteristics. Accurate and precise quantification of the acoustic field used in drug delivery experiments is essential to ensure safety versus efficacy and to avoid potentially harmful bioeffects.

Complications after ultrasonic lung parenchyma biopsy: a strong note for caution.

BACKGROUND: This study aimed to determine the possible cause for an unacceptable frequency of postresectional pneumothorax in cases of ultrasonic scalpel use without a further reinforcing maneuver in lung biopsy during video-assisted thoracic surgery (VATS). METHODS: Data for a series of 16 consecutive VATS lung biopsy patients (group A) in which a disturbingly high number of minor and medium complications occurred were compared with data for a group of 20 patients previously subject to the same ultrasonic lung biopsy method (group B) without complication. RESULTS: The two groups were identical in terms of all significant factors considered in relation to ultrasonic scalpel biopsy. Six notable air leakage complications occurred among the 16 patients of group A. One patient needed redrainage while still in the hospital. Two other patients required readmission and redrainage. In 4 of the 16 cases, late pneumothorax was detected after a "silent" 48-h postoperative period prolonging their hospital stay. Altogether, three medium complications occurred in group A, as compared with none in group B. The drainage duration in group B was not significantly shorter than in group A . Multivariate analysis showed a significant difference in complications favoring group B (odds ratio, 1.88). CONCLUSIONS: A high postoperative air leakage rate was observed in a simple case series using an unsecured harmonic scalpel after a randomized trial of the same method in the same institute with a diametrically opposite outcome. The medium complication rate of 3 in 16 cases is unacceptable for a minor procedure such as lung biopsy. The two groups differed only in their thromboembolic prophylaxis protocol. Therefore, it is hypothesized that the recent introduction of low-molecular-weight heparin from day 1 may influence the complication rate. The authors' observation calls for caution in use of the harmonic scalpel on lung tissue without reinforcing maneuvers (i.e., stitches or clips). To avoid unnecessary complications, operative technique adjustment is recommended.

Proximal ureteral calculi: shock wave or ureterolithotripsy?

OBJECTIVE: To compare the success rates and efficiency of ureterolithotripsy (URL) and extracorporeal shock wave lithotripsy (SWL) for proximal ureteric stones. CASUISTRY AND METHODS: A prospective non-randomized study was performed between 1999 and 2004. Of a total of 235 patients, 121 underwent SWL and 114 had ureteroscopy with ultrasonic lithotripsy. There were no significant differences between the groups. The success rate, operative time, postoperative pain and complications were analyzed in each group. Patients were followed postoperatively for a minimum of 3 months (median 6 months). RESULTS: Treatment success rate was defined as the complete removal or as the radiographic absence of calculi at a 3-month follow-up. The URL success rate was 85.6% (98/114) and 89.5% (68/95) after one SWL session and (77/85) 90.6% after a second treatment. No differences were found in the results, overall complication rates and mean procedure time. However, the fluoroscopy time was longer in the URL group and pain was more frequent. CONCLUSIONS: Semirigid URL is as efficient as SWL in the treatment for proximal ureteral stone. However, SWL requires less fluoroscopic time and fewer pain relievers.

Safety assurance in obstetrical ultrasound.

Safety assurance for diagnostic ultrasound in obstetrics began with a tacit assumption of safety allowed by a federal law enacted in 1976 for then-existing medical ultrasound equipment. The implementation of the 510(k) pre-market-approval process for diagnostic ultrasound resulted in the establishment of guideline upper limits for several examination categories in 1985. The obstetrical category has undergone substantial evolution from initial limits (ie, 46 mW/cm2 spatial peak temporal average [SPTA] intensity) set in 1985. Thermal and mechanical exposure indices, which are displayed onscreen according to an Output Display Standard, were developed for safety assurance with relaxed upper limits. In 1992, with the adoption of the Output Display Standard, the allowable output for obstetrical ultrasound was increased in terms of both the average exposure (eg, to a possible 720 mW/cm2 SPTA intensity) and the peak exposure (via the Mechanical Index). There has been little or no subsequent research with the modern obstetrical ultrasound machines to systematically assess potential risks to the fetus using either relevant animal models of obstetrical exposure or human epidemiology studies. The assurance of safety for obstetrical ultrasound therefore is supported by three ongoing means: (1) review of a substantial but uncoordinated bioeffect research literature; (2) the theoretical evaluation of diagnostic ultrasound exposure in terms of thermal and nonthermal mechanisms for bioeffects; and (3) the skill and knowledge of professional sonographers. At this time, there is no specific reason to suspect that there is any significant health risk to the fetus or mother from exposure to diagnostic ultrasound in obstetrics. This assurance of safety supports the prudent use of diagnostic ultrasound in obstetrics by trained professionals for any medically indicated examination.

Effect of different splint removal techniques on the surface roughness of human enamel: a three-dimensional optical profilometry analysis.

Because there is no standard protocol for the removal of resin-based materials that retain semi-rigid trauma splints on teeth, iatrogenic enamel damage caused by various splint removal techniques has remained unknown. The purpose of this study was to evaluate the effect of five different resin removal techniques (H6/H7 scaler, ultrafine diamond bur, ultrasonic scaler, 16-blade tungsten carbide bur, and Sof-Lex disks) on the surface roughness of human enamel. Three-dimensional white-light interferometry, a non-contact profilometry technique, was used to obtain qualitative and quantitative measurements of surface roughness both at baseline and after finishing procedures. Statistical analysis using Friedman test and Wilcoxon signed ranks test showed that the roughest enamel surface was obtained after splint removal with the hand scaler (P < 0.05). Overall, the smoothest enamel surface was obtained after removal of resin with Sof-Lex disks and the 16-blade tungsten carbide bur (P < 0.05).

[The influence of ultrasound and constant magnetic field on gametes, zygotes, and embryos of the sea urchin].

The influence of constant magnetic field, power 7 T, and ultrasound, frequency 2, 4 and 8 MHz, on gametes, fertization, embryos and larvae of the sea urchin was studied. It was shown that magnetic field breaks the process of the gamete fusion but does not influence gametes, embryos, and larvae. Ultrasound impairs the motility of spermatozoa and larvae, prevents the fertilization, and breaks the embryonic development. It is assumed that the effect of the magnetic field is connected with the response of the cortical cytoskeleton, which consists of bundles of actin microfilaments. The rearrangement of the cortical cytoskeleton occurs during the first 20 minutes after the contact of sperm with the egg. Also there is effect of magnetic fields on calcium ions, which are liberated during the first seconds after gamete contact. The effect of the ultrasound is explained by a small increase in water temperature and cavitation process, which break celluar structures.

[Methods for reducing traumatism of the posterior corneal epithelium during ultrasound phacoemulsification].

[Methods for reducing traumatism of the posterior corneal epithelium during ultrasound phacoemulsification]

HIFU procedures at moderate intensities--effect of large blood vessels.

A three-dimensional computational model is presented for studying the efficacy of high-intensity focused ultrasound (HIFU) procedures targeted near large blood vessels. The analysis applies to procedures performed at intensities below the threshold for cavitation, boiling and highly nonlinear propagation, but high enough to increase tissue temperature a few degrees per second. The model is based upon the linearized KZK equation and the bioheat equation in tissue. In the blood vessel the momentum and energy equations are satisfied. The model is first validated in a tissue phantom, to verify the absence of bubble formation and nonlinear effects. Temperature rise and lesion-volume calculations are then shown for different beam locations and orientations relative to a large vessel. Both single and multiple ablations are considered. Results show that when the vessel is located within about a beam width (few mm) of the ultrasound beam, significant reduction in lesion volume is observed due to blood flow. However, for gaps larger than a beam width, blood flow has no major effect on the lesion formation. Under the clinically representative conditions considered, the lesion volume is reduced about 40% (relative to the no-flow case) when the beam is parallel to the blood vessel, compared to about 20% for a perpendicular orientation. Procedures involving multiple ablation sites are affected less by blood flow than single ablations. The model also suggests that optimally focused transducers can generate lesions that are significantly larger (>2 times) than the ones produced by highly focused beams.

Biological effects of two successive shock waves focused on liver tissues and melanoma cells.

A new generator of two successive shock waves focused to a common focal point has been developed. Cylindrical pressure waves created by multichannel electrical discharges on two cylindrical composite anodes are focused by a metallic parabolic reflector - cathode, and near the focus they are transformed to strong shock waves. Schlieren photos of the focal region have demonstrated that mutual interaction of the two waves results in generation of a large number of secondary short-wavelength shocks. Interaction of the focused shockwaves with liver tissues and cancer cell suspensions was investigated. Localized injury of rabbit liver induced by the shock waves was demonstrated by magnetic resonance imaging. Histological analysis of liver samples taken from the injured region revealed that the transition between the injured and the healthy tissues is sharp. Suspension of melanoma B16 cells was exposed and the number of the surviving cells rapidly decreased with increasing number of shocks and only 8 % of cells survived 350 shocks. Photographs of cells demonstrate that even small number of shocks results in perforation of cell membranes.

Mechanism of the protective effects of long chain n-alkyl glucopyranosides against ultrasound-induced cytolysis of HL-60 cells.

Recently it has been shown that long chain (C5-C8) n-alkyl glucopyranosides completely inhibit ultrasound-induced cytolysis [J.Z. Sostaric, N. Miyoshi, P. Riesz, W.G. DeGraff, and J.B. Mitchell, Free Radical Biol. Med., 39 (2005) 1539]. This protective effect has possible applications in HIFU (high intensity focused ultrasound) for tumor treatment, and in ultrasound assisted drug delivery and gene therapy. n-Alkyl glucopyranosides with hexyl (5mM), heptyl (3mM), octyl (2mM) n-alkyl chains protected 100% of HL-60 cells in vitro from 1.057 MHz ultrasound-induced cytolysis under a range of conditions that resulted in 35-100% cytolysis in the absence of glucopyranosides. However the hydrophilic methyl-beta-d-glucopyranoside did not protect cells. The surface active n-alkyl glucopyranosides accumulate at the gas-liquid interface of cavitation bubbles. The OH radicals and H atoms formed in collapsing cavitation bubbles react by H-atom abstraction from either the n-alkyl chain or the glucose moiety of the n-alkyl glucopyranosides. Owing to the high concentration of the long chain surfactants at the gas-liquid interface of cavitation bubbles, the initially formed carbon radicals on the alkyl chains are transferred to the glucose moieties to yield radicals which react with oxygen leading to the formation of hydrogen peroxide. In this work, we find that the sonochemically produced hydrogen peroxide yields from oxygen-saturated solutions of long chain (hexyl, octyl) n-alkyl glucopyranosides at 614 kHz and 1.057 MHz ultrasound increase with increasing n-alkyl glucopyranoside concentration but are independent of concentration for methyl-beta-D-glucopyranoside. These results are consistent with the previously proposed mechanism of sonoprotection [J.Z. Sostaric, N. Miyoshi, P. Riesz, W.G. DeGraff, and J.B. Mitchell, Free Radical Biol. Med., 39 (2005) 1539]. This sequence of events prevents sonodynamic cell killing by initiation of lipid peroxidation chain reactions in cellular membranes by peroxyl and/or alkoxyl radicals [V. Misik, P. Riesz, Ann. N.Y. Acad. Sci., 899 (2000) 335].

The effects of high-intensity, low-frequency active sonar on rainbow trout.

This study investigated the effects on rainbow trout (Oncorhynchus mykiss) of exposure to high-intensity, low-frequency sonar using an element of the standard Surveillance Towed Array Sensor System Low Frequency Active (LFA) sonar source array. Effects of the LFA sonar on hearing were tested using auditory brainstem responses. Effects were also examined on inner ear morphology using scanning electron microscopy and on nonauditory tissues using general pathology and histopathology. Animals were exposed to a maximum received rms sound pressure level of 193 dB re 1 microPa(2) for 324 or 648 s, an exposure that is far in excess of any exposure a fish would normally encounter in the wild. The most significant effect was a 20-dB auditory threshold shift at 400 Hz. However, the results varied with different groups of trout, suggesting developmental and/or genetic impacts on how sound exposure affects hearing. There was no fish mortality during or after exposure. Sensory tissue of the inner ears did not show morphological damage even several days post-sound exposure. Similarly, gross- and histopathology observations demonstrated no effects on nonauditory tissues.

Stable and unstable chromosome aberrations measured after occupational exposure to ionizing radiation and ultrasound.

AIM: To evaluate chromosome aberration and fluorescent in situ hybridization (FISH) assays as a method to estimate of health risk, we monitored 9 male subjects occupationally exposed to low doses of both ionizing radiation and ultrasound during a period of over 3 years. METHODS: Sampling was performed at 6-month intervals during a three-year period. First we used conventional chromosomal aberrations analysis. When the aberration frequency for a particular subject reached the background, we measured translocations in the final sample, using fluorescence in situ hybridization. Chromosome painting probes for chromosomes 1, 2, and 4 were used simultaneously. RESULTS: Dicentric and ring chromosomes were eliminated within a year. Translocations persisted and deviated from control values in all examinees. Translocations were detected long after unstable aberrations decreased to the background level. CONCLUSION: Fluorescence in situ hybridization-based translocation detection was a reliable method for monitoring chronic occupational clastogen exposure. Chromosome aberration assay correlated with translocation frequency. Stable chromosomal aberrations reflected cumulative genome damage during job exposure.