Transducer Depth Research Articles

Weakly supervised video-based cardiac detection for hypertensive cardiomyopathy

IntroductionParameters, such as left ventricular ejection fraction, peak strain dispersion, global longitudinal strain, etc. are influential and clinically interpretable for detection of cardiac disease, while manual detection requires laborious steps and expertise. In this study, we evaluated a video-based deep learning method that merely depends on echocardiographic videos from four apical chamber views of hypertensive cardiomyopathy detection.MethodsOne hundred eighty-five hypertensive cardiomyopathy (HTCM) patients and 112 healthy normal controls (N) were enrolled in this diagnostic study. We collected 297 de-identified subjects’ echo videos for training and testing of an end-to-end video-based pipeline of snippet proposal, snippet feature extraction by a three-dimensional (3-D) convolutional neural network (CNN), a weakly-supervised temporally correlated feature ensemble, and a final classification module. The snippet proposal step requires a preliminarily trained end-systole and end-diastole timing detection model to produce snippets that begin at end-diastole, and involve contraction and dilatation for a complete cardiac cycle. A domain adversarial neural network was introduced to systematically address the appearance variability of echo videos in terms of noise, blur, transducer depth, contrast, etc. to improve the generalization of deep learning algorithms. In contrast to previous image-based cardiac disease detection architectures, video-based approaches integrate spatial and temporal information better with a more powerful 3D convolutional operator.ResultsOur proposed model achieved accuracy (ACC) of 92%, area under receiver operating characteristic (ROC) curve (AUC) of 0.90, sensitivity(SEN) of 97%, and specificity (SPE) of 84% with respect to subjects for hypertensive cardiomyopathy detection in the test data set, and outperformed the corresponding 3D CNN (vanilla I3D: ACC (0.90), AUC (0.89), SEN (0.94), and SPE (0.84)). On the whole, the video-based methods remarkably appeared superior to the image-based methods, while few evaluation metrics of image-based methods exhibited to be more compelling (sensitivity of 93% and negative predictive value of 100% for the image-based methods (ES/ED and random)).ConclusionThe results supported the possibility of using end-to-end video-based deep learning method for the automated diagnosis of hypertensive cardiomyopathy in the field of echocardiography to augment and assist clinicians.Trial registrationCurrent Controlled Trials ChiCTR1900025325, Aug, 24, 2019. Retrospectively registered.

Effect of Sonication Frequency and Power Intensity on the Disruption of Algal Cells: Under Vacuum and Non-Vacuum Conditions

The presence of algae caused by anthropogenic eutrophication in water has become a severe environmental issue. Various treatment options for algae removal have been developed, such as filtration, coagulation, sedimentation, flotation, algicides, ozone, and photolysis. However, these technologies are complex, expensive, consume considerable amounts of various chemicals, and may cause further pollution (i.e., by-product formation). Ultrasonic exposure is an alternative method for removing algae from water that is environmentally friendly (i.e., no addition of chemicals) and almost unaffected by any turbidity in the water. In this study, process optimization of ultrasonication (e.g., by adjusting frequency, power intensity, and exposure time) for the removal of alga was tested under vacuum and non-vacuum conditions. Experiments were conducted on a batch of algae solution in a clear glass tube ultrasonicated by a 20 kHz transducer for 180 minutes. The tube was depressurized up to -67 N/m2 in a depressurizing chamber. The data was collected at transducer depths of 0.06, 0.13, and 0.19 m. It was concluded that the optimum condition (i.e., 92% algal cell disruption) was achieved when the power intensity was 7 kWh/m3, under vacuum conditions, at a frequency of 20 kHz and 180 minutes of exposure time. Higher power intensity gave higher energy for cell disruption, moreover by depressurizing the air above the algae solution, the lysis effect for algae reduction increased from 20% to 70% compared to the non-depressurized system due to higher cavitation bubble production. In addition, the depth of the transducer was another factor that could increase the lysis of the algae water. Therefore, this technology has future potential application for algae removal from water.

Single Treatment, Single Depth Superficial Microfocused Ultrasound with Visualization for Rhytid Improvement.

Background:Standard lifting and tightening protocols with microfocused ultrasound with visualization (MFU-V, Ultherapy) comprise the use of multiple transducer depths. We developed a shortened, single depth treatment protocol for patients seeking skin rejuvenation.Methods:Single-center, prospective case series. Subjects with static periorbital wrinkles, perioral wrinkles, or accordion lines had a single MFU-V treatment comprising up to 340 lines (periorbital 120, perioral 100, and accordion 120) with the superficial depth transducer (10.0 MHz/1.5 mm). Efficacy was assessed using established rating scales as well as clinician- and subject-reported Global Aesthetic Improvement Scales at baseline, 90, and 180 days, and each subject served as their own control. Adverse events were documented.Results:Nine subjects, women aged 38–64, received treatment. At 180 days, post treatment clinicians reported visible improvements in periorbital lines (6/6 cases), accordion lines (5/6 cases), and perioral lines (3/6 cases). Subjects’ self-assessments mirrored those of the clinicians, reporting improvements in accordion lines (5/6 cases improved, 1/6 cases much improved), periorbital lines (3/6 cases improved, 3/6 cases much improved) and perioral lines (2/6 cases improved, 2/6 cases much improved). Subject-rated satisfaction was high (accordion lines 6/6 cases, periorbital lines 4/6 cases and perioral lines 4/6 cases). All subjects experienced mild, transient erythema; in one subject, wheals persisted for 24 hours, resolving on application of mild topical corticosteroid.Conclusions:Shortened protocol, single depth MFU-V treatment was well-tolerated. It provided aesthetic improvements in periorbital and accordion lines, and to a lesser extent in perioral lines. Its utility as a noninvasive therapy for superficial skin rejuvenation warrants further investigation.

Assessment of Temporal Bone Thickness for Implantation of a New Active Bone-Conduction Transducer.

To investigate the minimum bone thickness in adults and children in the area of the skull affected by implantation of a new bone conduction device in patients without known medical history that indicates anatomical malformations. Retrospective, non-interventional study on computer tomography (CT) scans on file at a university medical center. A digital model of the new bone conduction implant was virtually implanted in 3D reconstructions of temporal bones based on 197 CT scans, 132 from adults and 65 from children (evenly distributed in five different age groups). The bone thickness was measured in a total of 11 designated positions; five measurement points for the transducer (recess area), and six for the fixation screws, corresponding to three different positions for the fixation band holding the implant in place (screw area). The minimum bone thickness in the combined recess and screw area for adults was 5.55 ± 1.46 mm, with a 95% CI of 5.30 to 5.80 mm. For children, the thickness was 4.34 ± 2.29 mm (95% CI: 3.77-4.91 mm), increasing from 1.92 mm (0-4 yr) to 6.41 mm (12-14 yr). For all ages, the bone in the recess area was generally thicker compared with the screw area.With an implantation depth of 3 mm the transducer fitted in all of the adult temporal bones (100%) and 99.2% (131/132) of the adults had a bone thickness of at least 2.7 mm in all six measured screw positions. In all children from the age of 5 the transducer fitted at an implantation depth of 3 mm, and in all children from the age of 9, the fixation screws fitted at a depth of 2.7 mm. In all CT scans except for a 6-month-old child the new bone conduction device could be implanted in at least one of the fixation band positions analyzed. In adults and many children without known medical history that indicates anatomical malformations, the average minimum bone thickness was thicker than both the maximum transducer depth of 3 mm and the 2.7 mm bone involvement of the osseointegrating fixation screws. The results indicate implant fit of the new bone conduction implant in all adult patients. The risks of compromising the sigmoid sinus and the dura as considered with larger implants are thus significantly reduced. Preoperative planning with CT would still be recommended for children below 9 years old.

Study of the feasible size of a bone conduction implant transducer in the temporal bone.

The aim was to assess the temporal bone volume to determine the suitable size and position of a bone conduction implant (BCI) transducer. A BCI transducer needs to be sufficiently small to fit in the mastoid portion of the temporal bone for a majority of patients. The anatomical geometry limits both the dimension of an implanted transducer and its positions in the temporal bone to provide a safe and simple surgery. Computed tomography (CT) scans of temporal bones from 22 subjects were virtually reconstructed. With an algorithm in MATLAB, the maximum transducer diameter as function of the maximum transducer depth in the temporal bone, and the most suitable position were calculated in all subjects. An implanted transducer diameter of 16 mm inserted at a depth of 4 mm statistically fitted 95% of the subjects. If changing the transducer diameter to 12 mm, a depth of 6 mm would fit in 95% of the subjects. The most suitable position was found to be around 20 mm behind the ear canal. The present BCI transducer casing, used in ongoing clinical trials, was designed from the results in this study, demonstrating that the present BCI transducer casing (largest diameter [diagonal]: 15.5 mm, height: 6.4 mm) will statistically fit more than 95% of the subjects. Hence, the present BCI transducer is concluded to be sufficiently small to fit most normal-sized temporal bones and should be placed approximately 20 mm behind the ear canal.

Basis of acoustic discrimination of chinook salmon from other salmons by echolocating Orcinus orca

The "resident" ecotype of killer whales (Orcinus orca) in the waters of British Columbia and Washington State have a strong preference for Chinook salmon even in months when Chinook comprise less than about 10% of the salmon population. The foraging behavior of killer whales suggests that they depend on echolocation to detect and recognize their prey. In order to determine possible cues in echoes from salmon species, a series of backscatter measurements were made at the Applied Physics Laboratory (Univ. of Wash.) Facility on Lake Union, on three different salmon species using simulated killer whale echolocation signals. The fish were attached to a monofilament net panel and rotated while echoes were collected, digitized and stored on a laptop computer. Three transducer depths were used; same depth, 22° and 45° above the horizontal plane of the fish. Echoes were collected from five Chinook, three coho and one sockeye salmon. Radiograph images of all specimens were obtained to examine the swimbladder shape and orientation. The results show that echo structure from similar length but different species of salmon were different and probably recognizable by foraging killer whales.

Backscatter measurements of three species of salmon using simulated killer whale echolocation signals.

The resident ecotype of killer whales (Orcinus orca) in the waters of British Columbia and Washington State has a strong preference for Chinook salmon even in months when Chinook are 5%–10% of the salmon population. The foraging behavior of killer whales suggests that they rely on echolocation to detect and recognize their prey. In order to determine possible cues in echoes from salmon, a series of backscatter measurements was made at the Applied Physics Laboratory, University of Washington Facility on Lake Union, on three different salmon species using simulated killer whale echolocation signals. The fish were tied to a monofilament net and rotated while echoes were collected, digitized, and stored on a laptop computer. Three transducer depths were used; same depth, 22o, and 45o above the horizontal plane of the fish. Echoes were collected from five Chinook, three Coho, and one Sockeye salmon. Radiograph images of all the specimens were also obtained to examine the swim bladder shape and orientation. Res...

Pre-spawning herring in a protected area showed only moderate reaction to a surveying vessel

We studied the influence of a surveying vessel on the behaviour of shallowly distributed local pre-spawning herring ( Clupea harengus L.) in a protected area in the Trondheimsfjord (West Norway). The vessel passed an acoustic buoy at standard survey speed at a distance of 10–40 m four times at night and seven times by day. Bottom depths ranged from 40 to 60 m and a herring layer consisting mostly of pre-spawners was recorded from transducer depth (2.5 m) down to 15–30 m. The herring mass centre was deeper during vessel passage than during undisturbed reference periods, indicating a diving reaction. Backscattered echo energy also decreased during most passages, but the trend was less consistent than increased centre depth, especially during night-time passages. In summary, indications of vessel avoidance were weaker than those previously reported for herring in the same period. We interpret vessel avoidance as the reaction to a perceived threat, and the weak response was unexpected. Pre-spawning herring should act in order to maximise their chances of survival until reproduction and a strong reaction to perceived threats as documented from earlier studies was therefore expected. The shallowness of the location in combination with many gadoids close to the bottom, as observed acoustically, may have been important factors that attenuated the reaction of the fish to the vessel in our study.

Three-Dimensional Trajectory Assessment of an IVUS Transducer From Single-Plane Cineangiograms: A Phantom Study

The recovery of the three-dimensional (3-D) path of the transducer used during an intravascular ultrasound (IVUS) examination is of primary importance to assess the exact 3-D shape of the vessel under study. Traditionally, the reconstruction is done by simply stacking the images during the pullback, or more recently using biplane angiography to recover the vessel curvature. In this paper, we explain, how single-plane angiography can be used with two projection models, to perform this task. Two types of projection geometry are analyzed: weak-perspective and full-perspective. In weak-perspective projection geometry, the catheter path can be reconstructed without prior transducer depth information. With full-perspective projection geometry, precise depth location of reference points are needed in order to minimize the error of the recovered transducer angle of incidence. The transducer angulation reconstruction is based on the foreshortening effect as seen from the X-ray images. By comparing the measured to the true transducer length, we are able to get its incidence angle. The transducer trajectory is reconstructed by stitching together the different estimated angulations obtained from each image in a cineangiogram sequence. The method is described and validated on two helical vessel phantoms, giving on average a reconstructed path that is less than 2 mm distant from the true path when using full-perspective projection.

A Closed Form Slug Test Theory for High Permeability Aquifers

We incorporate a linear estimate of casing friction into the analytical slug test theory of Springer and Gelhar (1991) for high permeability aquifers. The modified theory elucidates the influence of inertia and casing friction on consistent, closed form equations for the free surface, pressure, and velocity fluctuations for overdamped and underdamped conditions. A consistent, but small, correction for kinetic energy is included as well. A characteristic velocity linearizes the turbulent casing shear stress so that an analytical solution for attenuated, phase shifted pressure fluctuations fits a single parameter (damping frequency) to transducer data from any depth in the casing. Underdamped slug tests of 0.3, 0.6, and 1 m amplitudes at five transducer depths in a 5.1 cm diameter PVC well 21 m deep in the Plymouth-Carver Aquifer yield a consistent hydraulic conductivity of 1.5 x 10(-3) m/s. The Springer and Gelhar (1991) model underestimates the hydraulic conductivity for these tests by as much as 25% by improperly ascribing smooth turbulent casing friction to the aquifer. The match point normalization of Butler (1998) agrees with our fitted hydraulic conductivity, however, when friction is included in the damping frequency. Zurbuchen et al. (2002) use a numerical model to establish a similar sensitivity of hydraulic conductivity to nonlinear casing friction.

Ultrasound transmitting configuration

An ultrasound transmitting configuration includes at least one ultrasound generating device for exposing a medium which has an acoustic medium impedance and a medium speed of sound to ultrasonic waves. The ultrasound generating device has at least two ultrasound transducers which can be excited through actuating electrodes for emitting ultrasound and which have an acoustic transducer impedance. The ultrasound transducers are separated from one another and disposed alongside one another. An ultrasound lens which has an acoustic lens impedance and a lens speed of sound is disposed between the ultrasound generating device and the medium. The ultrasound generating device is acoustically coupled on a coupling side to the ultrasound lens. The ultrasound transducers extend toward the medium over a transducer depth, they extend toward one another over a transducer width, and they extend at right angles to both the transducer depth and the transducer width over a transducer length. The transducer width is maximally as great as the transducer depth, and the transducer length is considerably greater than the transducer depth. The ultrasound transducers are associated with a common actuating element for actuating the ultrasound transducers jointly and in the same way.

Target strength analysis in high fish densities using a probing split beam transducer

Unbiased measurements of the mean target strength are needed if the absolute fish abundance is to be measured. For most pelagic fish, this also requires direct target strength techniques to work in high-density situations. A probing, pressure stabilized split beam transducer has been lowered from the research vessel directly into dense herring layers in order to resolve a single target at short range. Specialized hardware has been used for single fish target tracking, from which data on target strength, target directivity, swimming speed and tilt angle are derived. The paper will focus particularly on calibration procedures for transducer depth performance, target-tracking methodology and on the monitoring of essential transducer movement parameters.

Some problems and solutions for the measurement of fish target strength: A study case with Atlantic redfish (Sebastes spp.)

Potential biases in the measurement of redfish target strength (TS) were examined by comparing ex situ and in situ approaches. Ex situ experiments were conducted on individuals after developing a method to maintain live fish in good condition. The main problem with the manipulation of these species was the inflation and distortion of the swimbladder. To minimize this bias, fish were kept in sea cages after acclimation at depth and TS was measured in a camera-monitored apparatus set in proximity to the capture site. A series of in situ acoustic-trawl experiments was conducted on several aggregations of redfish in Newfoundland waters. TS were collected using a hull-mounted EK500 split-beam transducer and a deep-tow dual-beam system. The dual-beam transducer was calibrated at different depths to test if change in pressure and/or temperature affected its sensitivity. This system was used to measure aggregations of fish under different transducer depth. The data indicated that biases in in situ TS estimates increased with the range of observation, the density of fish, and the presence of multiple targets formed by the clustering of smaller organisms. Depending on the nature of the bias, TS can be over- or underestimated by as much as 6 dB.

A Portable Retractable ADCP Boom-Mount for Small Boats

This paper describes the design, testing, and application of a portable and retractable shipboard acoustic Doppler current profiler (ADCP) boom-mount. The boom is specifically adapted for small fiberglass boats working with a minimal crew. The design permits the rapid collection of ADCP data on discontinuous transects which would be difficult or impossible using a large displacement hull vessel or with a towed vehicle. This capability is particularly useful in shallow wind-driven estuaries and in tidal channels where flow time scales are often on the order of several hours. Tests of the boom show that high quality ADCP data (as measured by percent good) can be obtained at boat speeds up to 4.0 m s−1 and that data quality depends on transducer depth. The utility of the retractable design is demonstrated with an 8 m boat on two nearly synoptic ADCP surveys of a shallow estuary. With minor modifications to accommodate different vessel geometries, the design could be readily adapted for use on similar vessels.

An Autonomously Recording Inverted Echo Sounder: ARIES II

Abstract A self-contained instrument, the Autonomously Recording Inverted Echo Sounder (ARIES II), carrying two 250-kHz beam side-scan sonars and with the capacity to record sonar data sampled at 3.2 kHz for 168 h with the sonars operating with a pulse repetition rate of 2 Hz, has been constructed and tested in a mooring deployment that lasted for 25 days near the edge of the continental shelf west of Scotland. The mean water depth was 146 m. ARIES II was positioned at a mean transducer depth of 34.6 m with sonars directed upward at 20° to the horizontal to obtain acoustic returns from targets at or near the sea surface. The instrument was preprogrammed to record continuously over periods of 2, 4, and 13 h, the last to cover the M2 tidal cycle dominant in the area. Sonographs are presented to illustrate observations of surface waves and wave groups, internal solitons, rain showers, and Langmuir circulation. An analysis is made of the effects of surface waves, currents, and internal waves on the instrument...

Effect of Ultrasound Transducer Depth Setting in Identifying the Presence and Spatial Extent of Myocardial Perfusion Defects During Rest and Dobutamine Stress With Intermittent Harmonic Imaging

Effect of Ultrasound Transducer Depth Setting in Identifying the Presence and Spatial Extent of Myocardial Perfusion Defects During Rest and Dobutamine Stress With Intermittent Harmonic Imaging

Effect of ultrasound transducer depth setting in identifying the presence and spatial extent of myocardial perfusion defects during rest and dobutamine stress with intermittent harmonic imaging

Effect of ultrasound transducer depth setting in identifying the presence and spatial extent of myocardial perfusion defects during rest and dobutamine stress with intermittent harmonic imaging

Application of adiabatic mode theory to the calculation of horizontal refraction through a mesoscale ocean eddy

Adiabatic mode theory is used to calculate the path in the horizontal plane of vertical acoustic normal modes (at a frequency of 25 Hz) that have propagated through an idealized gulf-stream eddy of radius 125 km whose center is 625 km from the source. The arrival directions of the modes (which are calculated using a simple algorithm) and their relative amplitudes are used to calculate the apparent bearing of the source at positions beyond the eddy (the algorithm cannot be applied to positions within the inhomogeneity) on a line at 5° to the source-center axis. For source and receivers at a depth of 600 m, the source bearing deviation decreases from 0.5° at 740 km to 0.4° at 860 km (its asymptote, as range becomes infinite, is zero). The results for a transducer depth of 600 m are compared with a previously published calculation based on a parabolic equation method that used identical eddy parameters and transducer configurations. The two methods are found to predict broadly the same bearing deviation, except that the adiabatic mode-theory predictions are around 0.04° smaller than the average parabolic equation predictions. The effect of coupling from other modes on the amplitude of the important mode is found to be only 2% and hence negligible. For the eddy model considered, the degree of horizontal refraction of normal modes decreases as the mode number is increased. The bearing deviation therefore increases as the depth of the transducers is increased.

High-frequency sound attenuation caused by the wind-generated bubble layer in the open sea

Sound attenuation along vertical paths for high-frequency beams is calculated using a semi-empirical formula for the distribution of wind-generated bubbles in the open sea [Novarini and Bruno, J. Acoust. Soc. Am. 72, 510–514 (1982)]. These calculations are carried out numerically for frequencies between 70 and 150 kHz, wind speeds up to 30 kn and different transducer depths. The results are fitted with a simple formula.

Shallow Water Sound Propagation Studies in an Intermediate Scale Model

A one-half square mile of constant water depth of about 10 ft is situated close to Pacific Naval Laboratory in the Esquimalt Lagoon and forms a natural intermediate scale model tank for shallow water propagation studies. Bottom velocities and layering depths have been obtained from a seismic survey. The dependence of sound level of a cw signal on transmitter depth at range to depth ratios of 30, 45, 60, 75, 90, 105 has been obtained for the first three modes of propagation. The received sound level from a transducer moved at constant depth towards the receiver has been recorded with acoustic wavelength and transducer depth as parameters. Instrumentation to (a) permit rapid measurement of vertical temperature profiles from a remote position, and (b) to record surface wave amplitude at the Tx and Rx position has been installed. Fluctuations in level of received cw signals appear well-correlated in frequency with surface waves. The dependence of the percentage of fluctuations on (a) surface wave amplitude, and (b) acoustical wavelength has been determined. A wave packet experiment, using the bow wave from a boat to produce the sound fluctuations, throws some light on the mechanism involved.