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PubMed2006

[Root canal therapy of resinified teeth with surgical operating microscope and ultrasonic instruments].

PURPOSE: To evaluate the role of surgical operating microscope and ultrasonic instruments in endodontic treatment of patients who underwent previous resinifying therapy. METHODS: 63 premolars and molars that had been treated with resinifying therapy before were selected for root canal therapy. The coronal portion of resinified root canals were negotiated with ultrasonic instruments under surgical operating microscope, and the apical portion was managed with small size hand files and 15% EDTA. The root canals of all cases were shaped by Nickel-Titanium rotary instruments Hero 642, and obturated with lateral condensation technique. The negotiation of root canal system, instrument fracture, alterations of canal morphology, and operation time were recorded. The efficiency of preparation and obturation was analyzed by radiographs before and after treatment. RESULTS: The root canals of 54 teeth were negotiated, enlarged and obturated, with a success rate of 85.7%. No complications were found, such as vertical fracture, ledge, perforation and instrument separation. Good result of treatment was achieved in the 54 cases. CONCLUSIONS: The use of surgical operating microscope and ultrasonic instruments is proved to be effective in negotiation of coronal portion of the resinified root canals. Nevertheless, the use of ultrasonic instruments in apical or curved portion of root canals is not encouraged.

Aged↗
PubMed1995

Ultrasonic resection of neuroblastomas. Long-term local tumor control.

OBJECTIVE: To evaluate the effectiveness of ultrasonic aspiration in achieving local tumor control of bulky neutroblastomas that are considered unresectable by conventional means. DESIGN: A retrospective review of 12 patients undergoing ultrasonic aspiration as part of multimodal treatment protocols. SETTING: A pediatric oncology referral center. PATIENTS: Twelve children with large neuroblastomas located in the abdomen (n = 5), chest (n = 5), and neck (n = 2). Follow-up was 1.5 to 7.5 years. INTERVENTIONS: Ultrasonic aspiration of the tumor was primary therapy (n = 7) or followed initial chemotherapy (n = 5). All patients underwent subsequent chemotherapy or autologous bone marrow transplantation. MAIN OUTCOME MEASURES: The incidences of residual disease and local recurrence were examined. RESULTS: Tumor-related symptoms were effectively relieved in all 12 patients. Recurrent local disease led to death in two. One patient died of distant metastases. CONCLUSIONS: Ultrasonic aspiration minimized blood loss and did not cause damage to adjacent organs. It provided nearly complete tumor resection, enhanced the effectiveness of chemotherapy protocols, and decreased the need for supportive care. Ultrasonic aspiration is a safe and effective method for obtaining local control of large neuroblastomas.

Abdominal Neoplasms↗
PubMed2005

Image retrieval with principal component analysis for breast cancer diagnosis on various ultrasonic systems.

OBJECTIVES: We present a computer-aided diagnostic (CAD) system with textural features and image retrieval strategies for classifying benign and malignant breast tumors on various ultrasonic systems. Effective applications of CAD have used different types of texture analysis. Nevertheless, most approaches performed in a specific ultrasonic machine do not indicate whether the technique functions satisfactorily for other ultrasonic systems. This study evaluated a series of pathologically proven breast tumors using various ultrasonic systems. METHODS: Altogether, 600 ultrasound images of solid breast nodules comprising 230 malignant and 370 benign tumors were investigated. All ultrasound images were acquired from four diverse ultrasonic systems. The suspicious tumor area in the ultrasound image was manually chosen as the region-of-interest (ROI) subimage. Textural features extracted from the ROI subimage are supported in classifying the breast tumor as benign or malignant. However, the textural feature always behaves as a high-dimensional vector. In practice, high-dimensional vectors are unsatisfactory at differentiating breast tumors. This study applied the principal component analysis (PCA) to project the original textural features into a lower dimensional principal vector that summarized the original textural information. The image retrieval techniques were employed to differentiate breast tumors, according to the similarities of the principal vectors. The query ROI subimages were identified as malignant or benign tumors according to characteristics of retrieved images from the ultrasound image database. RESULTS: Using the proposed CAD system, historical cases could be directly added into the database without a retraining program. The area under the receiver-operating characteristics curve for the system was 0.970+/-0.006. CONCLUSION: The CAD system identified solid breast nodules with comparatively high accuracy in the different ultrasound systems investigated.

Area Under Curve↗
PubMed2000

Ultrasonic vocalization by female mice in the presence of a conspecific carrying food cues.

In female mice, Mus domesticus, reunion with a same-sex conspecific is associated with intense ultrasonic vocalization. We examined whether the palatability of a familiar food eaten by a demonstrator mouse and the motivational state of the conspecific observer could modulate the number of ultrasonic calls uttered during female-female interaction in NMRI mice. A pilot study indicated that these calls were uttered almost exclusively by the observer member of the pair. Observers were either food deprived or not deprived and demonstrators were offered either no food, a palatable diet or an unpalatable diet. We monitored both the number of ultrasounds (range 65-75 kHz) uttered and a series of behavioural parameters during the first 3 min of social interaction after 24 h of separation. Observers investigated the nose area of demonstrators fed on the unpalatable diet more than the same area of demonstrators not given food. No differences were found in demonstrators' behaviour. Ultrasonic calls were given immediately after female-female reunion and were affected by both the motivational state of the observer and the salience of the information carried by the conspecific. These results suggest that the motivational state of the observer affects ultrasonic calling towards a demonstrator conspecific. Nondeprived animals produced more calls towards demonstrators fed on palatable food, whereas food-deprived subjects vocalized more to fed conspecifics, independently of the palatability of the food eaten by the demonstrator. We suggest that ultrasonic vocalization in female mice can facilitate proximity with a conspecific and the number of these calls is modulated by the salience of the information carried by the companion. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Ultrasonic Monitoring of Oil-in-Water Emulsions Undergoing Depletion Flocculation

The paper describes a three-part experiment on flocculating emulsions in order to determine whether ultrasonic spectroscopy could be used to detect and characterize the flocculation process. Three emulsions which represented unflocculated, partially flocculated, and fully flocculated systems were prepared. They were characterized independently using direct microscopic examination and their creaming behavior. Ultrasonic spectroscopic measurements of the flocculating emulsions showed large changes during the flocculation process, which were not readily modeled using single particle scattering theory. The ultrasonic properties of the unflocculated emulsion did not change during the measurement period. The results demonstrate that ultrasonic techniques are capable of detecting the flocculation process. There is clear potential to use ultrasonic techniques to characterize flocculated structures, but more work is needed on the theoretical analysis of the interaction of ultrasound with particle aggregates. Copyright 1997Academic Press

Journal Article↗
PubMed1978

The breakdown of spectrin produced by ultrasonication.

The application of carefully controlled ultrasonication to human erythrocyte membranes (ghosts) has been found to produce a selective breakdown of the two spectrin polypeptides. This breakdown increases with the time and the intensity of ultrasonication. The 240 000 molecular weight spectrin polypeptide is slightly more susceptible to ultrasonication than the 220 000 molecular weight polypeptide. Isolated spectrin behaves in an identical manner when ultrasonicated. When highly purified samples of spectrin are ultrasonicated the progressive reduction of the molecular weight of the products with increasing time is clearly apparent.

Erythrocyte Membrane↗
PubMed1993

The present status of ultrasonic imaging in medicine.

The ultrasonic techniques that are used routinely in medical imaging have resulted from basic scientific discoveries, new methods of signal analysis and image processing, the development of transducer materials and fabrication techniques, and the application of digital electronics. The system designer is constrained by the ultrasonic properties of tissues, especially speed and attenuation: these properties determine the optimum choices of ultrasonic frequency, and spatial contrast and temporal resolutions. Ultrasonic Doppler techniques provide information about moving targets, including blood flow. Two-dimensional images of anatomical structure and blood flow can be combined in real-time displays. Other advances include sonoelasticity imaging, computed tomography, three-dimensional imaging, contrast agents and quality assurance. Contemporary ultrasonic diagnostic techniques seem to be safe, but the search for possible hazards is continuing with emphasis on thermal effects and cavitation.

Blood Flow Velocity↗
PubMed1991

Ultrasonic cavitation indirectly induces single strand breaks in DNA of viable cells in vitro by the action of residual hydrogen peroxide.

Direct exposure of cells to vigorous ultrasonic cavitation results predominantly in mechanical cell lysis, but latent effects due to production of toxic sonochemicals can also be present. Phosphate buffered saline (PBS) was exposed to 1.61 MHz ultrasonic cavitation at 20 degrees C in a rotating tube exposure system to build up sonochemical products. Single strand DNA breaks (SSBs) were then induced by treating Chinese hamster ovary (CHO) cells with the cavitated PBS for 30 min on ice. The SSBs resided in viable cells, as evidenced by their ability to repair the breaks when warmed. This indirect effect could be explained by the action of cavitation-generated hydrogen peroxide that had built up (e.g., to 16 microM after 30 min exposure) in the PBS. Dissolution of argon gas in the PBS before exposure enhanced the SSB effect and the H2O2 production. Addition of catalase to the cavitated PBS before cell treatment eliminated the H2O2 and the SSB gamma effect. Tests with hydrogen peroxide showed that 16 microM H2O2 treatment for 30 on ice was as effective as 1 Gy dose of 60Co gamma rays in producing single strand breaks. The SSB effect of H2O2 and gamma rays was reduced by addition of the radical scavenger cysteamine to the cells before treatment, but cysteamine did not reduce the SSB effect of direct exposure to ultrasonic cavitation. These results help to clarify the potential for genetic effects from ultrasonic cavitation. These effects help to clarify the potential for genetic effects from ultrasonic cavitation.

Animals↗
PubMed2004

Ultrasonic transducers working in the air with the continuous wave within the 50-500 kHz frequency range.

Transmitting and receiving ultrasonic waves in the air requires high standards of both the transmitters and the receivers of these waves. The paper presents the results of measurements of ultrasonic signals generated by ultrasonic transducers of mean power working with the continuous wave, designed for operating in the air at the frequencies between 50 and 500 kHz. The characteristic feature of these transducers is their high effectiveness and sensitivity, which are necessary for working in the transmission system. Directional characteristics' measurements and the measurements of the acoustic field in the air enabling its visualization on different planes were done on specially built research setups. The results of the measurements of these transducers' admittance were also presented. Because of the forecast applications of these transducers for examining ultrasonic signals transmitted in the air by materials with different degrees of porosity, obtaining the high energy of the generated ultrasonic wave is necessary. This was possible thanks to applying layers of acoustic impedance Z approximately (0.2/1.0)x10(6) kg/(m2 s) matching the high impedance of ceramics with the low impedance of air. The designed and produced transducers had the normalized diameter of D=38 mm and worked at frequencies within the ranges of f=50, 200, 350 and 500 kHz.

Journal Article↗
PubMed2004

Autoresonant control of nonlinear mode in ultrasonic transducer for machining applications.

Experiments conducted in several countries have shown that the improvement of machining quality can be promoted through conversion of the cutting process into one involving controllable high-frequency vibration at the cutting zone. This is achieved through the generation and maintenance of ultrasonic vibration of the cutting tool to alter the fracture process of work-piece material cutting to one in which loading of the materials at the tool tip is incremental, repetitive and controlled. It was shown that excitation of the high-frequency vibro-impact mode of the tool-workpiece interaction is the most effective way of ultrasonic influence on the dynamic characteristics of machining. The exploitation of this nonlinear mode needs a new method of adaptive control for excitation and stabilisation of ultrasonic vibration known as autoresonance. An approach has been developed to design an autoresonant ultrasonic cutting unit as an oscillating system with an intelligent electronic feedback controlling self-excitation in the entire mechatronic system. The feedback produces the exciting force by means of transformation and amplification of the motion signal. This allows realisation for robust control of fine resonant tuning to bring the nonlinear high Q-factor systems into technological application. The autoresonant control provides the possibility of self-tuning and self-adaptation mechanisms for the system to keep the nonlinear resonant mode of oscillation under unpredictable variation of load, structure and parameters. This allows simple regulation of intensity of the process whilst keeping maximum efficiency at all times. An autoresonant system with supervisory computer control was developed, tested and used for the control of the piezoelectric transducer during ultrasonically assisted cutting. The system has been developed as combined analog-digital, where analog devices process the control signal, and parameters of the devices are controlled digitally by computer. The system was applied for advanced machining of aviation materials.

Journal Article↗
PubMed2004

Ultrasonic band gaps and negative refraction.

The first experimentally observed ultrasonic band gaps in periodic bidimensional composited are reviewed here. The studied basic structure consists of an aluminum alloy plate with a periodic arrangement of cylindrical holes filled with mercury. Localization phenomena in linear and point defects have been observed and an ultrasonic waveguide capable to bend the ultrasonic radiation by 90 degrees has been achieved. We also revisit twinned-square periodic structures for ultrasonic wave bending and splitting. Such devices allow 45 degrees bending of waves, whereas an extreme anomalous refraction law at the grain boundaries has also been experimentally observed. Finally, a preliminary study about the possibility of "left-handed" behaviour in ultrasonic crystals is presented in this work. The device consists of a slab of the above mentioned metallic composite attached to an epoxy wedge. In this system, clues to negative refraction are theoretically shown.

Journal Article↗
PubMed2004

Ultrasonic fields radiated through matching layers with nonparallel boundaries.

In the case of ultrasonic measurements in aggressive media piezoelectric elements of ultrasonic transducers are separated from a medium by thick protective layers, which may posses nonparallel front and back surfaces. This enables to reduce significantly the amplitude of multiple reflections, but the structure of the ultrasonic field radiated through a layer with nonparallel boundaries becomes complicated. The main objective of this paper is to present a method suitable for simulation of ultrasonic fields radiated through a layer with nonparallel boundaries in a transient mode. The proposed simulation method is based on the transformation of a multilayered medium into a virtual one without internal boundaries, equivalent to the actual medium from the point of a view of the relative times of arrival of direct and edge waves. The simulated ultrasonic fields in water are compared with the measurement results and a good correspondence between calculated and measured fields is obtained.

Journal Article↗
PubMed2004

A new technique for the identification of ultrasonic flaw signals using deconvolution.

The identification of ultrasonic flaw signals is a difficult task in the angle beam ultrasonic testing of welded joints due to the presence of non-relevant signals from the geometric reflectors such as weld-roots and counter-bores. This paper describes a new approach to identify ultrasonic flaw signals in such a problematic situation. A similarity function is defined as the deconvolution of a target signal by a reference signal. The similarity functions for the same type of flaws/references are symmetric bandlimited impulse-like patterns with larger amplitudes while those for different types of flaws/references are asymmetrical broad patterns with relatively smaller amplitudes. Therefore, ultrasonic signals could be identified by the pattern of the similarity function. In the initial experiments, the proposed technique showed great potential for identifying ultrasonic flaw signals in the inspection of weld joints.

Journal Article↗
PubMed2004

Effects of ultrasonic energy on dyeing of polyamide (microfibre)/Lycra blends.

Although ultrasonic energy is widely used cleaning and degreasing of parts and assemblies in automotive and other industries, the use of ultrasonic energy in an industrial scale for textile washing is very new. This is due to the complexity of controlling the combination of chemical and mechanical effects, whereas with degreasing of machine parts only the mechanical effects is applied. The use of ultrasonic energy in dyeing PA/Lycra fabrics with reactive dyes has been studied spectrophotometrically in this work. PA/Lycra (85/15) blends have been dyed using conventional and ultrasonic dyeing techniques with three reactive dyes containing different chromophore and reactive groups. The dyeing carried out conventionally and by the use of ultrasonic techniques. The results were compared in terms of percentage exhaustion; total dye transferred to the washing bath after dyeing and the fastness properties.

Journal Article↗
PubMed2004

In-line ultrasonic monitoring of semi-solid magnesium die casting process.

Ultrasonic velocity and attenuation measurements in AZ91D magnesium (Mg) alloy with dendritic, rosette and globular microstructures were performed at elevated temperatures using a non-contact laser-ultrasonic technique. It was found that the ultrasonic velocity in the globular microstructure and the ultrasonic attenuation in the dendritic microstructure are the highest among the three microstructures. An ultrasonic clad steel buffer rod sensor embedded in the die has been used to monitor the semi-solid die casting process in-line for the AZ91D Mg alloy. This probe monitored the completion of the die filling, the release of the pressure, the opening of the die, part detachment, solidification of the part, the averaged temperature of the die and the part.

Journal Article↗
PubMed2005

The influence of ultrasonic-vibration on hot upsetting of aluminum alloy.

The traditional ultrasonic apparatus cannot be operated at high temperature, explaining why the effect of ultrasonic-vibration on high temperature metal forming has seldom been addressed in literature. This study establishes an ultrasonic-vibration hot upsetting system. A cooling mechanism is used to solve the problem of high temperature. The effects of temperature and strain rate during ultrasonic-vibration on the upsetting of aluminum alloy were explored using this new system. Experimental results indicate that ultrasonic-vibration can considerably reduces the compressive forces during hot upsetting. The reducing effect on compressive forces decreases while the temperature increases. The strain rate does not significantly affect the reducing effect on compressive forces.

Journal Article↗
PubMed2005

A model-based inverse method for positioning scatterers in a cladded component inspected by ultrasonic waves.

Nondestructive methods aim at detecting, locating and identifying defects. Inversion of ultrasonic measurements obtained by inspecting a steel component of regular geometry with an immersed transducer leads to accurate location of defects. When the component is cladded, the irregular geometry of the surface and the anisotropic nature of the cladding material lead to aberrations of the radiated field (e.g., beam distortions, splitting and defocusing, these varying with the transducer scanning position). As a consequence, defect location may be inaccurate and defects (e.g., cracks) sizing impossible. In the present paper, a model-based inverse method is developed to solve this problem. It relies on the time-dependent simulation of ultrasonic propagation in this material of complex geometry and structure, in order to determine a set of probable positions for the defect at the origin of the measured ultrasonic echo-structure. The most probable position is determined by minimizing a cost-function of likeness between the simulated and measured ultrasonic images. The overall scheme shall generally apply to inverse measured ultrasonic echo-structures as soon as the simulation of the forward problem is tractable. To validate the method, examples of application are given dealing with actual measurements obtained in the real configuration of pressure vessel inspection.

Journal Article↗
PubMed2005

Wavelet based noise suppression technique and its application to ultrasonic flaw detection.

The noise suppression techniques with wavelet transform (WT) are widely used in non-destructive testing and evaluation (NDT&E), especially in ultrasonics. Complete reconstruction theory with hard or soft thresholds, reconstruction technique based on the singularities of noise and signal, matched filter with an impulse response, and optimal frequency-to-bandwidth ratio of wavelet technique have all been used to analyze ultrasonic signals for noise suppression. But a more simple and effective technique has been pursued for decades. This paper develops a new technique using WT for the right purpose. In this work, WT is treated as a band-pass filter whose central frequency and frequency bandwidth (CF&FB) are determined by the spectra distribution of an ultrasonic signal captured from real testing situation. For the purpose of matching their CF&FB well, a technique for evaluating the optimal scale of a daughter wavelet is carried out too. By acting this daughter wavelet as a band-pass filter, we can obtain excellent de-noising results, even when the signal to noise ratio (SNR) is below -18 dB. The performance of the technique has been done by ultrasonic signals with computer generated white noises. Finally, the experimental verification is performed on a pipeline specimen with man-made small flaws with good results obtained. The results show that the technique is more suitable for processing heavy noised ultrasonic signals, and it can also be used in automatic flaw detection.

Journal Article↗