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PubMed1991

Ultrasonic propagation in slurries.

Experimental measurements have been made of the ultrasonic velocity and attenuation in some simple suspensions of, mainly, silicon carbide in water and in ethylene glycol. These are compared with theoretical predictions based on a novel hydrodynamic model. Predicted ultrasonic velocities are in excellent agreement with the measured values. Predicted and measured ultrasonic attenuations do not agree as well. However, the suspensions give rise to excess attenuations rising to a few hundred nepers per metre and special experimental techniques were needed to measure ultrasonic properties. To predict attenuations to within, say, 20% for mixtures such as these is a major achievement.

Carbon↗

PubMed1981

A microprocessor-based ultrasonic limb movement monitoring system.

A system has been devised, using a spark-gap ultrasonic transmitter and an array of four ultrasonic receivers, to monitor the unrestrained movement of a physically handicapped child's fingertip as he attempts to perform some specific task. A microprocessor is used to measure the time taken for a pulsed ultrasonic shock-wave to travel from the fingertip-mounted spark-transmitter to each of the four ultrasonic receivers, and hence compute the Cartesian co-ordinates of the transmitter. It is hoped that this equipment will enable the voluntary components in the poorly-controlled limb movements of some of the physically handicapped children to be isolated and used to control external equipment.

Child↗

PubMed1994

Analysis of ultrasonic scattering in blood via a continuum approach.

Since the pioneering work by Reid et al. on measuring ultrasonic scattering in blood, this phenomenon has been extensively studied both theoretically and experimentally. The knowledge on ultrasonic scattering properties of blood is needed for the design of ultrasonic methods for measuring blood flow, and a better interpretation of ultrasonic images. The development of high frequency intravascular or intracardiac imaging devices raises the possibility of measuring blood properties, e.g., erythrocyte aggregation and fibrinogen concentration, in situ. A number of theoretical approaches have been developed to analyze this phenomenon where in general ultrasound wavelength is much greater than the erythrocytes. These results show that the backscattering coefficient of blood, defined as power backscattered by a unit volume of blood per steradian per unit incident intensity, is proportional to variance of the erythrocyte number fluctuation and backscattering cross-section of a single erythrocyte. In this paper, we will show that similar results can also be obtained by taking a continuum approach.

Blood↗

PubMed2005

Rat ultrasonic vocalization in aversively motivated situations and the role of individual differences in anxiety-related behavior.

Our previous work has shown that male Wistar rats, although identical in breeder, age and housing conditions, can differ systematically in their anxiety-related behavior as measured in the elevated plus-maze. Since such individual dispositions can affect the responsiveness in other aversively motivated situations, we asked in a 1st experiment whether such rats might also differ in a test of conditioned fear. Based on their levels of spontaneous open arm avoidance in the elevated plus-maze, 20 adult male Wistar rats were divided into those with "high open arm" (HOA) versus "low open arm" (LOA) time. These rats were then tested in a standard fear conditioning paradigm. During the conditioning procedure, they received 6 tone (3 kHz, 20 s) and shock (0.5 mA, 0.5 s) pairings, each followed by a 60 s inter-stimulus interval. Conditioned responses to the tone were tested 24 h thereafter. During both days, freezing behavior and ultrasonic vocalization were measured. Differences in ultrasonic vocalization between HOA and LOA rats were detected during the conditioning day, where vocalization was more likely in LOA rats. Furthermore, LOA rats emitted calls with higher frequency components than HOA rats. On the subsequent day of testing, the number of animals vocalizing, and the rate of vocalization was decreased, and call differences between groups were no longer detectable. In freezing, differences between HOA and LOA rats were observed on the conditioning day, where LOA rats showed more freezing behavior during the tone/shock intervals. Also, on the test day, they showed more freezing behavior during the tone intervals compared to HOA rats. These results indicate that acute and conditioned responses of rats in a conventional fear conditioning paradigm can depend on individual dispositions of anxiety-related behavior as measured with the elevated plus-maze. In a 2nd experiment, we asked whether exposure to an elevated plus-maze would lead to ultrasonic vocalization, which we tested in rats which had been handled or non-handled prior to testing. Most importantly, we found that none of the animals displayed any vocalization in the plus-maze, neither during a 1st nor a repeated test 1 day later. These data are discussed with respect to the presumed role of ultrasonic vocalization in aversively motivated situations, and the mechanisms, which may account for the behavioral differences between HOA and LOA rats in such tests.

Analysis of Variance↗

PubMed2005

Extraction of oil from Jatropha curcas L. seed kernels by combination of ultrasonication and aqueous enzymatic oil extraction.

Use of ultrasonication as a pretreatment before aqueous oil extraction and aqueous enzymatic oil extraction was found to be useful in the case of extraction of oil from the seeds of Jatropha curcas L. The use of ultrasonication for 10 min at pH 9.0 followed by aqueous oil extraction gave a yield of 67%. However, the maximum yield of 74% was obtained by ultrasonication for 5 min followed by aqueous enzymatic oil extraction using an alkaline protease at pH 9.0. Use of ultrasonication also resulted in reducing the process time from 18 to 6 h.

Enzymes↗

PubMed2004

Ultrasonic and dielectric study of nonequilibrium monosaccharide solutions in water.

Based on broadband acoustical (10 kHz < or = nu < or = 2 GHz) and dielectric (1 MHz < or = nu < or = 40 GHz) spectrometry, time-resolved ultrasonic attenuation coefficient and static permittivity measurements have been performed on nonequilibrium tautomer solutions of d-arabinose and d-fructose in water. Via the chair-chair ring inversion the ultrasonic attenuation measurements display the decrease in the content of beta-arabinopyranoside and the increase of the alpha-fructopyranoside concentration during the establishment of the tautomer equilibrium. For the arabinose solutions, the mutarotation decay constant (m=(0.027+/-0.004) min(-1), 20 degrees C) from the ultrasonic measurements almost agrees with that from optical activity observations. For d-fructose the ultrasonic decay constant (m=(0.043+/-0.007) min(-1), 20 degrees C) is smaller than that from rotary polarization (m=0.054 min(-1), 20 degrees C) and dielectric permittivity (m=(0.058+/-0.007) min(-1), 20 degrees C), likely because the latter methods probe parallel pathways in the tautomer equilibrium whereas the former one reflects only one pathway.

Arabinose↗

PubMed2004

Nonsurgical ultrasonic endodontic instruments.

The advent of nonsurgical ultrasonic tips has opened up a new horizon in endodontic treatment. There are a number of nonsurgical endodontic ultrasonic systems currently available in the market and it is difficult to renew all of them. Based on similarities among different instrument systems, and attempt has been made to classify instruments into broad categories. This article describes the utility of each type of ultrasonic tip and the principles behind its usage. These instruments may be area specific or use specific, but can be used in an area other than the one for which they are specifically designed if the general principles regarding ultrasonic tips are understood and applied.

Dental Alloys↗

PubMed2006

Adaptive reconstruction of pipe-shaped human organs from 3D ultrasonic volume.

In this paper, we introduce an adaptive scheme for reconstructing pipe-shaped human organs from the volume data acquired by 3D ultrasonic devices. No other methods but the contour-based scheme was used in the process of reconstructing the volume data into a 3D polygonal surface. In the first step, the algorithm extracts contours from the sampled slices of the volume data using the modified radial gradient method, in which the points are sampled on the boundary of the region of interest by radiating rays and connected through making use of the chain code algorithm. The contours are represented as the context-free grammar, and their parsing trees are traversed during the reconstruction. The generated polygonal surface is refined as the contours are being refined at the casting of the new rays between the existing rays to sample new points and to modify the contours according to these newly derived points. An adaptive scheme is achieved in casting the rays adaptively on the slices. The proposed algorithm is to be applied in reconstructing the pipe-shaped human organs, such as arteries or blood vessels, to a polygonal surface. In this paper, we present an innovative tiling algorithm that reconstructs pipe-shaped human organ from 3D ultrasonic datasets. A set of contours on slices through the ultrasonic datasets is extracted using a modified radial gradient method, and our algorithm tiles these to make a polygonal surface. The tiling is performed by traversing a set of parsing trees which represent the contours in a context-free grammar. This makes our algorithm more efficient than previous algorithms that reconstruct surfaces from a set of contours. The first step of the algorithm is to determine a contour on each slice of the 3D ultrasonic dataset. After removing unwanted artifacts from the slice by applying several noise-removing operators, the centroid pixel of region of interest on the slice is designated. A radial gradient method casts a set of rays from the centroid pixel to the boundary of the slice and computes the intersection points between the rays and the boundary cells of the object so as to determine the contours. The second step uses context-free grammar that represents the contours. Each edge of a contour can be classified into six categories according to its relation with the rays cast from the centroid pixel, and the contour can then be represented by a string in a context-free grammar whose terminal symbols are the six types of the edges. A polygonal surface between two contours is constructed by traversing the parsing trees of the contours and determining the corresponding edges. The third step is to refine the smooth surface constructed in the second step by casting more rays. Additional rays refine the contour by decomposing the edges on the contour and convert leaf node of the parsing tree to the root of a new sub-tree whose leaf nodes denote the newly created edges. Our algorithm was tested on a phantom object and an artery from the neck. Results show that the performance of the algorithm and the quality of the resulting surface are better than those of existing algorithms. We have implemented a navigation facility that allows users to investigate the pipe-shaped human organs interactively.

Algorithms↗

PubMed2005

Nonlinear explanation for bone-conducted ultrasonic hearing.

Human listeners can perceive speech from a voice-modulated ultrasonic carrier presented via a bone-conduction stimulator. This study explored the psychoacoustic characteristics and underlying mechanisms of ultrasonic hearing by measuring difference limens for frequency (DLF) for pure tones modulated onto ultrasonic carriers. Human subjects were presented with two pulsed tones and asked to judge whether the first or the second had the higher pitch. When amplitude modulation was based on a double side-band transmitted carrier, the DLFs were as small as those from the air-conducted pure tones at 0.25-4 kHz. Ultrasounds yielded larger DLFs for tones with low (0.125 kHz) and high (6-8 kHz) frequencies. Results were essentially identical between the two types of carriers, sine wave (30 kHz) and bandpass noise (30+/-4 kHz), despite the different bandwidths in the ultrasonic range. When amplitude modulation was based on a double side-band suppressed carrier, DLFs corresponded to those from tones with double frequencies. These results suggest nonlinear conduction that demodulates audible signals from ultrasounds and provides inputs to the cochlea.

Acoustic Stimulation↗

PubMed2005

An ultrasonic device for source to skin surface distance measurement in patient setup.

PURPOSE: To develop an ultrasound-based source to skin surface distance (SSD) measurement technique and device for patient setup and test its feasibility and accuracy. METHODS AND MATERIALS: The ultrasonic SSD measurement device (USD) prototype consists of two main parts: a probe plate with an ultrasonic transducer in the center and a control unit that displays the SSD in millimeters. The probe plate can be slid into the block tray accessory slot of any treatment machine at the time of the SSD measurement. The probe plate contains an ultrasonic transducer as both the source and the detector for measuring the distance between the transducer and the target surfaces on the basis of an echo-detecting technique. The device was calibrated by a mechanical ruler with an accuracy of 0.01 mm and corrected by an offset of 601.7 mm, which is the distance from the radiation source to the ultrasonic transducer surface for the Siemens Primus linear accelerator (Linac). The ultrasound device provided digital readout with an accuracy of +/-0.1 mm for a flat surface after calibration. The SSD measurement experiments were done with the USD, an optical distance indicator (ODI), and an AKTINA 53-104 Mechanical Front Pointer (FP) on a Siemens Primus Linac with a full-sized female phantom. Ten measurements were carried out at each gantry angle of 0 degrees , 52 degrees , 85 degrees , 90 degrees , and 227 degrees for anatomic locations of head, thorax, breast, and pelvis, to obtain the average values and standard deviations. RESULTS: The comparison study with the ODI and FP showed that the USD had an accuracy of less than +/-1.0 mm and that USD measurements had the minimum standard deviations among the three methods; therefore, USD gave more consistent and accurate readouts for SSD measurement. When considering the FP as a reference, the USD yields smaller deviations than the ODI for all measured locations (less than +/-2 mm). The variation of USD digital readout with a room temperature change of +/-2 degrees C is +/-0.1 mm, which is sufficiently accurate for SSD measurement. CONCLUSIONS: The USD method has the following advantages. First, it decreases patient setup time by avoiding problems related to the blocking of the device by the patient or by the immobilization device. Second, it is more accurate than the other two methods currently used, as the test data show. Last, the digital readout eliminates the possibility of human reading error associated with the visual scales.

Calibration↗

PubMed2006

Ultrasonic model and system for measurement of corneal biomechanical properties and validation on phantoms.

Non-invasive measurement of biomechanical properties of corneas may provide important information for ocular disease management and therapeutic procedures. An ultrasonic non-destructive evaluation method with a wave propagation model was developed to determine corneal biomechanical properties in vivo. In this study, we tested the feasibility of the approach in differentiating the mechanical properties of soft contact lenses as corneal phantoms. Three material types of soft contact lenses (six samples in each group) were measured using a broadband ultrasound transducer. The ultrasonic reflections from the contact lenses were recorded by a 500MHz/8-bit digitizer, and displayed and processed by a PC. A reference signal was recorded to compute the normalized power spectra using Fast Fourier Transformation. An inverse algorithm based on least-squares minimization was used to reconstruct three parameters of the contact lenses: density, thickness, and elastic constants lambda+2micro. The thickness of each sample was verified using an electronic thickness gauge, and the averaged density for each type of lenses was verified using Archimedes' principle and manufacturer's report. Our results demonstrated that the ultrasonic system was able to differentiate the elastic properties of the three types of the soft contact lenses with statistical significance (P-value<0.001). The reconstructed thicknesses and densities agreed well with the independent measurements. Our studies on corneal phantoms indicated that the ultrasonic system was sensitive and accurate in measuring the material properties of cornea-like structures. It is important to optimize the system for in vivo measurements.

Biomechanical Phenomena↗

PubMed2004

Modified polyethylenimines as non-viral gene delivery systems for aerosol gene therapy: investigations of the complex structure and stability during air-jet and ultrasonic nebulization.

Polyelectrolyte complexes between DNA and polyethylenimine (PEI) are promising non-viral delivery systems for pulmonary inhalation gene therapy and thus require sufficient stability during nebulization. The structure and stability of four different PEI-DNA polyplexes, namely branched (bPEI), linear (linPEI), poly(ethylene glycol)-grafted PEI (PEGPEI), biodegradable (bioPEI) PEI with DNA, were investigated. Using atomic force microscopy, the morphology of DNA and polyplexes before and after both air-jet and ultrasonic nebulization was characterized. The influence of nebulization on physico-chemical properties, particle size and zeta potential, was studied. Efficient DNA condensation to spherical particles was achieved with bPEI (90 nm) and PEGPEI (110 nm). By contrast, incomplete DNA condensations, seen as flower structures, were observed with linPEI (110 nm) and bioPEI (105 nm). Air-jet nebulization altered the polyplex structure to a greater extent than ultrasonic nebulization and resulted mainly in smaller and non-spherical particles (30-200 nm). Ultrasonic nebulization did not change the spherical structure or particle size of the polyplexes. In particular, the shape and size of the PEGPEI polyplexes did not change. We conclude that ultrasonic nebulization is a milder aerosolization method for gene delivery systems based on PEI. Additionally, PEGPEI-DNA polyplexes seem to be more stable than their counterparts, which may be advantageous in pulmonary inhalation gene therapy.

Aerosols↗

PubMed2005

Mechanisms and kinetics models for ultrasonic waste activated sludge disintegration.

Ultrasonic energy can be applied as pre-treatment to disintegrate sludge flocs and disrupt bacterial cells' walls, and the hydrolysis can be improved, so that the rate of sludge digestion and methane production is improved. In this paper, by adding NaHCO3 to mask the oxidizing effect of OH, the mechanisms of disintegration are investigated. In addition, kinetics models for ultrasonic sludge disintegration are established by applying multi-variable linear regression method. It has been found that hydro-mechanical shear forces predominantly responsible for the disintegration, and the contribution of oxidizing effect of OH increases with the amount of the ultrasonic density and ultrasonic intensity. It has also been inferred from the kinetics model which dependent variable is SCOD+ that both sludge pH and sludge concentration significantly affect the disintegration.

Kinetics↗

PubMed2006

Decolorization of methyl orange by ozonation in combination with ultrasonic irradiation.

The combination of ultrasound and ozone for the decolorization of azo dye, methyl orange, was studied. The effect of ultrasonic power, ozone gas flow rate, gaseous ozone concentration, initial dye concentration, pH and hydroxyl radical scavenger on the decolorization of methyl orange was investigated. The results showed that the synergistic effect was achieved by combining ozone with ultrasonic irradiation for the decolorization of methyl orange. The synergistic effect was more significant when the system temperature was raised due to the heat effect of ultrasonic irradiation. The decolorization of methyl orange fits the pseudo first order kinetic model. The decolorization rate increased with the increase of ultrasonic power, ozone gas flow rate, gaseous ozone concentration. However, the decolorization rate decreased with the increasing initial dye concentration. Either pH or sodium carbonate has little effect on the decolorization rate, indicating that the low frequency ultrasound enhanced ozonation process for the decolorization of methyl orange is mainly a direct reaction rather than radical reaction.

Azo Compounds↗

PubMed2005

Computerized analysis of audible and ultrasonic vocalizations of rats as a standardized measure of pain-related behavior.

The behavioral assessment of experimental pain is essential for the analysis of pain mechanisms and the validation of therapeutic targets. Arthritic pain, in particular, is significantly associated with negative affective states and disorders. Here we present a standardized method for the quantitative analysis of audible and ultrasonic (25 +/- 4 kHz) vocalizations in awake rats as a measure of higher integrated behavior in a model of arthritic pain. A bat detector and a condenser microphone were used to record ultrasonic and audible vocalizations, respectively, in response to innocuous and noxious mechanical stimulation of the knee before and after induction of acute arthritis in one knee. A computerized system was used to analyze number and duration of the filtered signals. For the behavioral tests, the animal was placed in a customized recording chamber to ensure consistent stimulus application and stable recordings and to eliminate any movement-induced noise. Noxious stimuli produced stronger vocalizations than innocuous stimuli. Both audible and ultrasonic vocalizations to innocuous (allodynia) and noxious (hyperalgesia) stimuli increased after the induction of acute arthritis. These changes were accompanied by increased knee joint circumference, lowered hind limb withdrawal thresholds and reduced exploratory behavior in the same animals. The computerized analysis of audible and ultrasonic vocalizations is a valid, quantitative, reliable and convenient method to measure pain-related behavior.

Analysis of Variance↗

PubMed2006

Comparison of posttonsillectomy pain using the ultrasonic scalpel, coblator, and electrocautery.

OBJECTIVE: To compare postoperative tonsillectomy pain between 3 commonly used surgical devices: the Harmonic Ultrasonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH), the Coblator (ArthroCare Corp, Sunnyvale, CA), and electrocautery. STUDY DESIGN AND SETTING: A prospective, randomized trial. One hundred thirty-four patients were randomly assigned to receive a tonsillectomy with 1 of 3 surgical devices. All patients were asked to fill out a postoperative diary. RESULTS: Statistically significant differences in pain scores were revealed between the Coblator and electrocautery (P = 0.02) and between the Coblator and the Ultrasonic Scalpel (P = 0.003), with the Coblator having lower pain scores. Electrocautery and the Ultrasonic Scalpel did not differ significantly from each other. The Coblation method showed a strong trend toward quicker return to normal diet. CONCLUSION: Patients undergoing tonsillectomy with the Coblator device reported less pain over a 10-day period than patients undergoing tonsillectomy with electrocautery or the Ultrasonic Scalpel. Pain after tonsillectomy remains a major issue for our patients. The choice of surgical instrument appears to be one way to reduce this pain. EBM RATING: A-1b.

Adolescent↗

PubMed2004

Directing ultrasound at the cemento-enamel junction (CEJ) of human teeth: I. Asymmetry of ultrasonic path lengths.

The diagnosis of degenerative changes in human teeth is of general interest because early detections can avoid greater health problems and further weakening effects. Since the wear of teeth determines their stability and lifetime in relation to the physiological load, an ultrasonic survey of any dimensional changes of the enamel layer and especially of the dentin wall thickness may be very helpful. However, an ultrasonographic diagnosis requires first to determine the anisotropic human tooth properties at clinically relevant locations and to simulate wave propagation phenomena in inhomogeneous tooth models with proper dimensions. The first article of a series that provides modular data of mineralized tissues in human teeth at the cemento-enamel junction (CEJ) deals with an ultrasonic method for measuring the asymmetry of dimensional characteristics of extracted human teeth and their ultrasonic path lengths (UPL). Heavily attenuating tooth halves were investigated with respect to the symmetry of normal and inclined oppositely directed radial ultrasonic paths. The measured UPLs ranged from 1.2 mm to 4.4 mm. The relative difference in inclined UPLs between the left and the right tooth halves reaches almost 30%. This reveals a large asymmetry. The mean difference of angles that represent fastest path lengths was 2.2+/-8.1 degrees, which indicates large asymmetry and anisotropy. Several aspects, which are required for a proper integration of asymmetric data into models designed for medical element engineering and simulation (MEES), are discussed.

Algorithms↗

PubMed2005

Manipulation of cells using an ultrasonic pressure field.

A novel device is described that generates an ultrasonic force field in a fluid layer. The force field arises because of the acoustic radiation force, a second order effect, generated as an ultrasonic wave interacts with a suspended particle. This force field can be used to manipulate objects in the fluid layer trapped between this device and an arbitrary surface, in this case, a flat object slide. The device is shown to be capable of positioning and, in doing so, concentrating human cells to predictable locations. Mesenchymal and HeLa cells were used. Critically, the forces required to do this can be generated by ultrasonic pressure fields that do not affect the viability of the cells. The viability has been assessed using trypan blue dye. The device used consists of a 14 mm square glass plate that is excited by at least one of four piezotransducers attached to the edges. The resulting ultrasonic force field and, importantly, the location of the minima in the force potential at which the cells are collected, has been calculated analytically.

Cell Survival↗