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At least 811 records · Page 45Linked to original sources

PubMed1997

Ultrasonic effects on electroorganic processes Part 6. Formation of cupric carboxylates at a reactive copper anode in carboxylic acid solutions.

Current efficiency for the formation of highly soluble cupric acetate at a reactive (consumable) copper anode in an acetic acid solution was increased almost independently of current density under ultrasonic irradiation. On the other hand, the efficiency for sparingly soluble cupric oxalate depended complicatedly on current density. At a low current density region less than 4 mA cm(-2), ultrasonic irradiation caused an increase in the current efficiency, while at higher current densities no ultrasonic effect was observed because of the formation of a rigid oxalate film on the anode surface. This paper is the first report of ultrasonic effects on an electrochemical reaction at a reactive (consumable) anode which is stoichiometrically involved in the reaction leading to the formation of products derived from anode metal.

Journal Article↗

PubMed2000

Ultrasonic effects on electroorganic processes. Part 17. Product selectivity control in cathodic reduction of acrylonitrile

Product selectivity for adiponitrile, which was formed as the corresponding hydrodimeric product along with propionitrile as the hydromonomeric product in the cathodic reduction of acrylonitrile, was significantly increased under ultrasonic irradiation with an intensity above the ultrasonic cavitation threshold. This ultrasonic effect is rationalized as due to mass transport promotion of acrylonitrile molecules to the cathode surface from the bulk electrolytic solution by high speed jet streams caused by the cavitation. A mechanism for the ultrasonic effect is discussed in detail on the basis of the reaction pathway of the hydrodimerization of acrylonitrile.

Journal Article↗

PubMed2002

Clinical experience with a new ultrasonic and LithoClast combination for percutaneous litholapaxy.

OBJECTIVE: To assess a new lithotripter for intracorporal lithotripsy, which combines the mechanically driven pneumatic LithoClast (Electro-Medical Systems, Nyon, Switzerland) and a new ultrasonic device (Electro-Medical Systems), for use in percutaneous nephrolitholapaxy (PNL). PATIENTS AND METHODS: The new lithotripter consists of a LithoClast Master with 12 Hz repetition rate and a new ultrasonic device. The 1.0 mm LithoClast probe is advanced off-centre through the hollow 3.3 mm ultrasonic probe and protrudes about 1 mm. A new irrigation system with a pinch valve compressing the irrigation tube, a foot-switch for activating the ultrasound, the LithoClast and both together, and a stone bucket at the outlet tube are new features. Between February 1999 and August 2001, 68 patients were treated by PNL with the new device; 35 had complete and 33 had partial staghorn calculi. PNL was administered under fluoroscopic control and with the patient prone. RESULTS: The mean (range) duration of surgery was 61 (42-119) min. The complete stone-free rate was 66% after the first PNL; of the 68 patients, 16 received a second PNL, giving a final stone-free rate of 76% and 80%. The stone was composed of calcium oxalate monohydrate (COM) in 13%, COM with uric acid in 35%, apatite in 20% and cystine in 11%. Clinically the new lithotripter was very effective, producing smaller stone particles and thus fewer residual stone fragments after PNL than with the LithoClast or ultrasonic fragmentation alone. CONCLUSION: The new lithotripter provides easily managed and highly effective stone fragmentation of all stones, regardless of their composition.

Equipment Design↗

PubMed2005

Hepatic arterial doppler sonography in patients with cirrhosis and controls: observer and equipment variability with use of the ultrasonic contrast agent SHU 508A.

PURPOSE: The aims of this study on hepatic arterial Doppler sonography were to ascertain interobserver and interequipment variability, to investigate any potential artificial influence of the ultrasonic contrast agent on the Doppler measurements and to compare the results in healthy and cirrhotic subjects. METHODS: Doppler sonography of the left hepatic artery was performed in nine healthy and nine cirrhotic subjects by three independent observers using three different devices. Continuous infusion of the ultrasonic contrast agent SHU 508A and placebo were administered in a double blind fashion. Systolic, mean and end diastolic peak velocities as well as resistive and pulsatility indices were measured. RESULTS: Equipment associated variances (5.8 - 12.7 %) of the five Doppler parameters were greater than interobserver variances (0.3 - 3.6 %). No significant differences were observed between the velocities using ultrasonic contrast agent and placebo. Systolic (65.9 +/- 3.6 vs. 47.7 +/- 4.2 cm/s mean +/- SE, p = 0.02) and mean peak velocity (35.4 +/- 1.6 vs. 24.5 +/- 1.8 cm/s, p = 0.007) were significantly higher in cirrhotic than in healthy subjects whereas the resistive and pulsatility indices were not different. CONCLUSIONS: Doppler sonography of the left hepatic artery performed by various observers is reproducible as long as the same device is used. Under clinical conditions, velocities are correctly measured with the use of ultrasonic contrast agent and are elevated in patients with cirrhosis.

Adult↗

PubMed2006

[Digital ultrasonic diagnosis of lower leg venous thrombosis using harmonic imaging and cross beam technology].

PURPOSE: To evaluate the extent to which Tissue Harmonic Imaging (THI) and spatial averaging (Sono-CT, Cross Beam) facilitate the diagnosis of lower leg venous thrombosis. MATERIALS AND METHODS: In 100 cases of lower leg venous thrombosis, the conventional B-scan, THI, and ultrasonic CT technology (Cross Beam) in examinations using a multi-frequency transducer head (9 - 14 MHz, Logiq 9, GE) were compared during follow-up studies using compression sonography over at least 6 weeks. Two independent examiners performed digital image documentation (PACS connection) without modifying the gray level parameters optimized in the B-scan. A thrombosis was considered to be proven sonographically if at least one ultrasonic modality yielded findings reproducible in follow-up checks at a comparable site in accordance with both examiners. RESULTS: Thromboses in the V. tibialis posterior category (97 %) and the fibular category (81 %) were found most often, followed by muscular venous thromboses (48 %). Thromboses in the V. tibialis anterior category were rare (12 %). The procedure comparison showed an advantage for ultrasonic CT technology in terms of the demarcation of thromboses of the deeper veins (sensitivity 98 %), as compared to THI (sensitivity 87 %, specificity 91 %, PPV: 99 %) and the B-scan (sensitivity 81 %). CONCLUSION: If a high-resolution linear transducer is used, THI and ultrasonic CT-Technology can facilitate the diagnosis of a lower leg venous thrombosis.

Adult↗

PubMed1998

Modified soft-balloon methods during ultrasonic probe examination for superficial esophageal cancer.

BACKGROUND AND STUDY AIMS: In ultrasonic probe studies for early-stage esophageal cancer the original soft-balloon method utilizing a condom had succeeded in obtaining a clear and reproducible picture by keeping deaerated water in a condom; however, the condom, which covered the endoscope lens, eliminated the usual endoscopic sight. Therefore, the authors endeavored to develop a modified method which enables both normal endoscopic observation and ultrasonic probe study with only a single insertion of the endoscope. PATIENTS AND METHODS: Thirty-one patients with superficial esophageal cancer were included in this pilot study. As modifications of the soft-balloon technique, two novel methods of 'wrapping' and 'invagination' were developed. RESULTS: These modifications are considered to have solved the above-mentioned problem and enable one to acquire both normal endoscopic photos and ultrasonic probe images during the same insertion of the endoscope. CONCLUSION: In a pilot study novel modifications improved the method of ultrasonic probe study for superficial esophageal cancer.

Endosonography↗

PubMed1989

Dystocia in late labor: determining fetal position by clinical and ultrasonic techniques.

A failure of adequate progression during late labor occurs often and may prohibit an accurate determination of the fetal head position from scalp edema or caput formation. This investigation was undertaken to determine whether ultrasonic evaluation could confirm or correct the digital examination impressions of the fetal head position. Eighty-six attempted vaginal deliveries had recent evidence for arrested cervical dilation after 7 cm or more. An occiput transverse position in 24 (28%) cases was diagnosed accurately, with the need for additional ultrasonic information only in the presence of scalp edema. Distinguishing between a persistent occiput posterior (15 cases, 17%) or anterior (47 cases, 55%) position was often inexact by palpation alone. Combined clinical and ultrasonic impressions allowed for a significantly more precise diagnosis. Ultrasonic imaging allowed for more security while waiting, more confidence with midforceps application, or a prompter decision for cesarean section, depending on the head position.

Adult↗

PubMed1986

Ultrasonic absorption evidence for enhanced volume fluctuations in the tobacco mosaic virus protein helical aggregate.

The increased ultrasonic absorption brought about by self-assembly of biomolecules is analyzed for the assembly process from the 20S aggregate to the helical rod of tobacco mosaic virus protein in solution, designated here as the 20S --> P-helix transition. The analysis is based on theoretical developments in ultrasonic relaxation spectrometry presented previously and illustrates the possibility that this technique can be used for characterizing fluctuations. The analysis makes use of NMR data for the system in solution and of x-ray diffraction data for the closely related transition from the two-ring disk to the virion. These x-ray data comprise the high-resolution structures and the Debye-Waller temperature factors of the main chain atoms of both the two-ring disk in crystals and the virion in oriented gel form. First, reduced ultrasonic spectra are obtained for the 4S, 20S, and helical rod aggregates. The fluctuation-enhancement factor for the helical rod is determined independently of any deconvolution into normal modes of relaxation and is shown not to depend on the particular procedure of reduction employed. The increase of ultrasonic absorption in the 20S --> P-helix transition primarily reveals enhancement of the relaxing system's normal-mode volume fluctuations. The observed relaxations probably involve one conformational process per subunit. The normal-mode volume fluctuations are then estimated from a bimodal least-squares best fit to the data, and a lower bound for the reaction volume associated with the fast steps is obtained. Two mechanisms are considered as follows: (i) a destabilization process in which the free-energy difference between two states is reduced and (ii) an increase in reaction volumes of local conformation changes in the helical aggregate, resulting from the formation of a "carboxyl cage-like" structure and from the change in environment produced inside the cage. Increased reaction volumes would not be detected with x-ray diffraction. The possible occurrence of fluctuations at the RNA binding site raises the question of whether a quaternary structure that exhibits significant conformational fluctuations must be present for the binding of the nucleic acid.

Journal Article↗

PubMed2004

[Spatial and temporal control of ultrasonic fields via optoacoustic holography].

The present paper presents a new method for generating ultrasound, based on the interaction of laser-induced ultrasound generation and ultrasonic holography. An ultrasonic field generated in a water tank via the optoacoustic effect is spatially and temporally controlled: In order to produce defined ultrasonic frequencies in the MHz range, the laser pulses incident on a light-absorbing layer are modulated in time using an electro-optic modulator (EOM). Additionally, a high-resolution liquid crystal spatial light modulator (SLM) is used to imprint a pre-calculated phase front to the laser beam. A computer-generated binary hologram is also displayed at the SLM. The expanded laser beam projects the corresponding pattern to the plane absorptive layer in the water tank. The projection of specific patterns for the generation of ultrasonic beams resembles the use of, diffractive optical elements" in optics. Optical ultrasound generation with holographic steering is a flexible tool with promising numerous new applications in medical and technical ultrasound diagnostics.

Dose-Response Relationship, Radiation↗

PubMed1999

Incidence, ultrasonic patterns and resolution of nephrocalcinosis in very low birthweight infants.

This longitudinal study was undertaken in order to elucidate the incidence and natural course of nephrocalcinosis in preterm infants and to evaluate whether the ultrasonic classification for nephrocalcinosis used here is suitable for predicting subsequent resolution of the condition. A total of 129 very low birthweight infants were screened for nephrocalcinosis by renal ultrasonography at 2 wk, 6 wk and 3 mo. The pyramidal changes were classified as peripheral, scattered or extensive. Follow-up renal ultrasonography was performed on the infants with nephrocalcinosis at 6, 12, 18 and 24 mo, and thereafter annually up to 6 y of age, or until ultrasonic resolution. The overall incidence of nephrocalcinosis was 20% (26/129). Nephrocalcinotic changes were peripheral in 14 out of the 26 infants (54%), scattered in 7 (27%) and extensive in 5 (19%). Ultrasonic resolution had taken place in all the cases with peripheral nephrocalcinosis by 12 mo, but 3 of the 7 infants with the scattered pattern and 3 of the 4 with the extensive pattern (1 died) were still affected at 24 mo. In two cases with extensive nephrocalcinosis the condition still persisted at 5-6 y of age. We conclude that about 20% of very low birthweight infants develop nephrocalcinosis during the first 3 mo of life. In about half of the affected infants renal changes are restricted and transient, but more extensive forms may last several years. The classification of nephrocalcinosis used here is appropriate for predicting later ultrasonic resolution.

Anti-Inflammatory Agents↗

PubMed2004

Ureteral ultrasonic lithotripsy revisited: a neglected tool?

BACKGROUND AND PURPOSE: Ultrasonic lithotripsy was one of the first modalities used for treating renal and ureteral stones. However, in recent years, it has been largely replaced by newer techniques such as laser lithotripsy with rigid as well as flexible ureteroscopes. The aim of this study was to review the results and our current indications for ureteroscopic ultrasonic lithotripsy (UUL). PATIENTS AND METHODS: Between October 2000 and May 2002, 340 ureteroscopies were performed for the treatment of ureteral stones in the Rabin Medical Center. Of this series, 9 patients (2.6%) underwent UUL using a semirigid 8F ureteroscope (Wolf) and an Olympus ultrasonic lithotripter (LUS-1) with a 4.5F hollow probe. Four patients had Steinstrasse following shockwave lithotripsy, four had large (1-2-mm) ureteral stones, and one had an impacted calcified ureteral double-J stent. Stones >5 mm were initially fragmented by the holmium laser (550-microm fiber). A double-J stent was placed in all patients. The mean follow-up time was 20 months. RESULTS: The mean operative time was 84 minutes. No intraoperative complications occurred. The mean hospital stay was 3.9 days. Eight patients became stone free after the first procedure, and the other underwent secondary ureteroscopy, which rendered him stone free. CONCLUSIONS: Patients in whom UUL is performed are relatively complex stone patients. The use of ultrasonic lithotripsy following, or in combination with, laser or ballistic devices utilizes the unique properties of UUL, which combines stone fragmentation and efficient removal of small fragments. The technique was particularly useful in patients with Steinstrasse or a large stone burden. Thus, UUL has a limited but significant role in the treatment of ureteral stones.

Adult↗

PubMed1999

Ultrasonic measurement of the thickness of human articular cartilage in situ.

OBJECTIVE: The objective of the present study was to explore the possibility of using the ultrasonic pulse-echo technique for the non-invasive measurement of cartilage thickness in situ during a joint arthroscopic examination. The accuracy of the ultrasonic measurement was assessed in vitro against that of an established needling technique which is destructive. METHODS: The velocity of sound in articular cartilage was measured in an in vitro study of one set of ipsilateral human ankle and hip joints at 69 test sites. Its variability was determined. RESULTS: The velocity of sound in human articular cartilage measured in situ varied widely (1419-2428 m/s; mean: 1892 m/s; S.D. 183 m/s) and therefore the error in the thickness of cartilage obtained from ultrasonic measurement based upon a constant velocity of sound could be as large as 33.6% (mean 7. 38%; S.D. 6.25%). CONCLUSIONS: The ultrasonic pulse-echo technique is not accurate for the measurement of the thickness of cartilage in situ. An alternative (albeit minimally invasive) would be the needling technique. This requires the development of a specialized probe.

Aged↗

PubMed2004

Which cartilage is regenerated, hyaline cartilage or fibrocartilage? Non-invasive ultrasonic evaluation of tissue-engineered cartilage.

OBJECTIVE: To investigate ultrasonic evaluation methods for detecting whether the repair tissue is hyaline cartilage or fibrocartilage in new cartilage regeneration therapy. METHODS: We examined four experimental rabbit models: a spontaneous repair model (group S), a large cartilage defect model (group L), a periosteal graft model (group P) and a tissue-engineered cartilage regeneration model (group T). From the resulting ultrasonic evaluation, we used %MM (the maximum magnitude of the measurement area divided by that of the intact cartilage) as a quantitative index of cartilage regeneration. The results of the ultrasonic evaluation were compared with the histological findings and histological score. RESULTS: The %MM values were 61.1 +/- 16.5% in group S, 29.8 +/- 15.1% in group L, 36.3 +/- 18.3% in group P and 76.5 +/- 18.7% in group T. The results showed a strong similarity to the histological scoring. CONCLUSION: The ultrasonic examination showed that all the hyaline-like cartilage in groups S and T had a high %MM (more than 60%). Therefore, we could define the borderline between the two types of regenerated cartilage by the %MM.

Animals↗

PubMed1988

Particulate suspensions as ultrasonic contrast agents for liver and spleen.

Ultrasonic backscatter and attenuation coefficients of a medium can be increased by the addition of solid, micron-size inhomogeneities. A potentially useful agent for ultrasonic contrast of liver images has been identified. Iodipamide ethyl ester (IDE) particles can be produced in the form of dense, relatively incompressible solids with high impedance mismatch to water. The chemical, biochemical, and pharmacologic properties of the small, uniform diameter IDE particles permit safe intravenous injection followed by rapid accumulation of reticuloendothelial (RE) cells of the liver and spleen, and later elimination from these organs. Since the particles are phagocytized by RE cells, present in normal liver but not in tumors and many lesions, the selective enhancement of ultrasonic backscatter should improve detectability of lesions that are hypoechoic or isoechoic compared with surrounding tissue. The mechanisms of particle-ultrasound interaction may be described by relative motion attenuation, and scattering from a cloud of dense, incompressible spheres for the case of IDE particles in agar. Thus, values of attenuation and backscatter can be controlled by choice of ultrasound frequency and particle concentration and size. When the particles are accumulated in rat and rabbit livers, additional mechanisms induce attenuation and backscatter in excess of that predicted by IDE in agar. This preliminary work demonstrates that solid, biocompatible particles may be useful as an ultrasonic contrast agent.

Animals↗

PubMed1995

Efficacy of an ultrasonic surgical system for laparoscopic adrenalectomy.

PURPOSE: We determine the value of an ultrasonic surgical system for laparoscopic adrenalectomy. MATERIALS AND METHODS: We analyzed 16 patients who underwent laparoscopic adrenalectomy using the ultrasonic surgical system and compared the results with those of patients undergoing laparoscopic adrenalectomy without the system. RESULTS: The system simplified exposure of the renal pedicles and inferior vena cava, and facilitated adrenal separation from the perinephric fat as well as dissection and identification of the adrenal vessels. Operating time was shorter and blood loss was also less with use of the ultrasonic surgical system. CONCLUSIONS: The ultrasonic surgical system simplified laparoscopic adrenalectomy and made the operation much safer.

Adrenalectomy↗

PubMed2002

A comparison of two pachymetric systems: slit-scanning and ultrasonic.

PURPOSE: This article compares measurements of corneal thickness obtained with the Orbscan Topography System with those obtained with the ultrasonic pachymeter, when used to measure central-comeal thickness in normal subjects. METHODS: Slit-scan topography (Orbscan II system, version 3.0, Bausch & Lomb, Rochester, NY) and ultrasonic pachymetry (Ophthasonic A-Scan/ Pachometer III, Accutome, Malvern, PA) were used to measure central-corneal thickness in 92 right corneas of 92 healthy adult subjects. A correlation analysis was used to evaluate the relationship between both instruments. Measurements were also compared by plotting the difference between the methods against the average. The hypothesis of zero bias was examined by a paired t-test. The 95% limits of agreement also were calculated. RESULTS: The mean corneal thickness was 559.9 microm +/-3.73 SEM with the Orbscan system and 551.2 microm +/- 4.57 SEM with the ultrasonic pachymeter, values that were significantly different (paired t-test, P = 0.000). The coefficient of determination was 0.860 (y = -65.78 + 1.135 x; P = 0.000). The mean difference between the measurements from both devices was found to be significantly different from zero (mean: 8.74 microm; paired t-test; P = 0.000), with Orbscan being slightly higher than the Ophthasonic A-Scan. CONCLUSIONS: The Orbscan system measurements of central corneal thickness were greater than ultrasonic pachymeter measurements, a difference that was statistically significantly.

Adult↗

PubMed1997

Development and application of ultrasonic surgical instruments.

In this paper, a new approach for designing ultrasonic surgical instruments (USI) is presented. These medical instruments convert an ultrasonic signal into a mechanical vibration by utilizing a magnetostrictive method and have been found to be very useful for various medical procedures. The implemented system consists of an ultrasonic generator, a transducer, and waveguide instruments. The generator produces a high-current ultrasonic signal. The transducer converts this signal into a mechanical vibration. By use of the waveguide instrument, the vibration can be propagated and amplified. This new type of USI possesses a comprehensive ability to stop bleeding, cut bone tissues, regulate frequency automatically, control temperature, etc. The results from animal experiments and from human clinical operations show that the developed USI has the advantages in various aspects over the conventional equipment.

Abdominal Muscles↗

PubMed2001

Model-based estimation of ultrasonic echoes. Part I: analysis and algorithms.

The patterns of ultrasonic backscattered echoes represent valuable information pertaining to the geometric shape, size, and orientation of the reflectors as well as the microstructure of the propagation path. Accurate estimation of the ultrasonic echo pattern is essential in determining the object/propagation path properties. In this study, we model ultrasonic backscattered echoes in terms of superimposed Gaussian echoes corrupted by noise. Each Gaussian echo in the model is a nonlinear function of a set of parameters: echo bandwidth, arrival time, center frequency, amplitude, and phase. These parameters are sensitive to the echo shape and can be linked to the physical properties of reflectors and frequency characteristics of the propagation path. We address the estimation of these parameters using the maximum likelihood estimation (MLE) principle, assuming that all of the parameters describing the shape of the echo are unknown but deterministic. In cases for which noise is characterized as white Gaussian, the MLE problem simplifies to a least squares (LS) estimation problem. The iterative LS optimization algorithms when applied to superimposed echoes suffer from the problem of convergence and exponential growth in computation as the number of echoes increases. In this investigation, we have developed expectation maximization (EM)-based algorithms to estimate ultrasonic signals in terms of Gaussian echoes. The EM algorithms translate the complicated superimposed echoes estimation into isolated echo estimations, providing computational versatility. The algorithm outperforms the LS methods in terms of independence to the initial guess and convergence to the optimal solution, and it resolves closely spaced overlapping echoes.

Journal Article↗