Unique Doppler Research Articles

Abnormal mitral flow, what is the cause?

Diastolic mitral regurgitation is a unique Doppler finding that can be missed if special attention is not paid to it. There are a few causes of such abnormal flow, ranging from a conduction abnormality to abnormal valvular and left ventricle function. Failure to recognize it might lead to unnecessary investigations and delay the primary diagnosis. We are presenting a teaching case and discuss the associated pathology.

Ultrasonographic Demonstration of the Tissue Microvasculature in Children: Microvascular Ultrasonography Versus Conventional Color Doppler Ultrasonography.

Microvascular ultrasonographic imaging is the most recent and unique Doppler ultrasound technique. It uses an advanced clutter filter that can remove clutter artifacts and preserve the low-velocity microvascular flow signal. The potential advantages of microvascular ultrasonography are its superiority in detection and visualization of the small blood vessels in tissues, providing radiologists with more information on the vascular structures. Therefore, it has shown particular value in the clinical fields. The aim of this study was to provide microvascular ultrasonographic images for the tissue microvasculature, including the brain, thyroid gland, kidney, urinary bladder, small bowel, ovary, testis, lymph node, and hemangiomas in children, focusing on the comparison with conventional color Doppler ultrasonographic images.

Tuning the demodulation frequency based on a normalized trajectory model for mobile underwater acoustic communications

AbstractWe have developed a demodulator for low data rate, asynchronous frame, and narrow bandwidth underwater acoustic communication. We aim at operation under harsh conditions, ie, low signal‐to‐noise ratio, and across long distances. In this paper, we pay a special attention to the efficiency of mobility support. Mobility results into the Doppler effect, which, for a demodulator, makes the carrier frequency drift arbitrarily during attempts to decode frames. The chances of success are better when the demodulator can tune into the drifted carrier frequency. This can be achieved by trying a range of possible drifted carriers. We introduce the novel idea of normalized trajectory. Each normalized trajectory produces a unique Doppler shift pattern that can be applied to tune into a drifted carrier. We demonstrate that this improvement is theoretically sound. From a practical point of view, the search space is potentially reduced. The actual gain in performance is application‐specific and depends on the actual sets of trajectory parameters that are considered. We introduce the concept of normalized trajectory, discuss its integration into the demodulator, and review the performance of the new design.

Characterization of flow recirculation zones at the Perdigão site using multi-lidar measurements

Abstract. Because flow recirculation can generate significant amounts of turbulence, it can impact the success of wind energy projects. This study uses unique Doppler lidar observations to quantify occurrences of flow recirculation on lee sides of ridges. An extensive dataset of observations of flow over complex terrain is available from the Perdigão 2017 field campaign over a period of 3 months. The campaign site was selected because of the unique terrain feature of two nearly parallel ridges with a valley-to-ridge-top height difference of about 200 m and a ridge-to-ridge distance of 1.4 km. Six scanning Doppler lidars probed the flow field in several vertical planes orthogonal to the ridges using range–height indicator scans. With this lidar setup, we achieved vertical scans of the recirculation zone at three positions along two parallel ridges. We construct a method to identify flow recirculation zones in the scans, as well as define characteristics of these zones. According to our data analysis, flow recirculation, with reverse flow wind speeds greater than 0.5 m s−1, occurs over 50 % of the time when the wind direction is perpendicular to the direction of the ridges. Atmospheric conditions, such as atmospheric stability and wind speed, affect the occurrence of flow recirculation. Flow recirculation occurs more frequently during periods with wind speeds above 8 m s−1. Recirculation within the valley affects the mean wind and turbulence fields at turbine heights on the downwind ridge in magnitudes significant for wind resource assessment.

Observations of resonances and antiresonances in modal propagation over muddy sediment layer

Measurements of signals generated over the New England mud patch, an area of ocean roughly 70 m deep characterized by a 10 m thick surficial mud-layer, by the Intensity Vector Autonomous Recorder (IVAR) are presented. IVAR is a bottom deployed system that measures both potential and kinetic energy roughly 1.2 m above the seafloor. Data originate from signals generated by a towed J15 source (transmission in the 50–500 Hz band), and signal underwater sound (SUS) MK-64 explosive sources, both part of the SCE17 signal set, and individual modes are identified by their unique Doppler shifts and/or through time-frequency analysis of dispersion. The density contrast between water and mud manifests a concentration kinetic energy in the water column, specifically when the water/mud interface intersects a node of the vertical mode functions. Following the work of Tolstoy (JASA 28(6), 1182–1192, 1956), data observations are fit to a representative sediment model through coupling two reduced waveguides, one representing the water column and the other the layered sediment, at their lattice points. The persistence of a resonance, which occurs at intersecting lattice points, is examined in terms of the range dependence in water depth and sediment structure.

Mobile targets and sensor mobility in bat biosonar

Many species of echolocating bats pursue highly mobile prey such as flying insects. Target mobility poses a challenge when a prey executes escape maneuvers. In these cases, bats and their prey find themselves locked in evolutionary arms races. However, prey mobility also provides the bats with opportunities for solving the problem of detecting prey buried in clutter. This applies to active as well as passive biosonar. In passive biosonar, bats frequently listen to sounds that are generated involuntarily by the motion of a prey. In active biosonar, certain bat groups have evolved highly specialized biosonar systems to detect flying prey insects by virtue of unique Doppler signatures that are generated by the insect's wing beat. Since the Doppler shifts concerned are very small, this sensory feat requires a well-integrated suit of evolutionary specializations that include sonar signal design, cochlear filtering, representations all through the auditory system, and even adaptive behavioral control of the emitted frequencies. In addition to this complexity, bats with such a biosonar system also employ a peripheral mobility where the baffles for pulse emission and reception move rapidly during biosonar operation. It remains to be seen how these mobilities fit together to support the animal's sensory abilities.Many species of echolocating bats pursue highly mobile prey such as flying insects. Target mobility poses a challenge when a prey executes escape maneuvers. In these cases, bats and their prey find themselves locked in evolutionary arms races. However, prey mobility also provides the bats with opportunities for solving the problem of detecting prey buried in clutter. This applies to active as well as passive biosonar. In passive biosonar, bats frequently listen to sounds that are generated involuntarily by the motion of a prey. In active biosonar, certain bat groups have evolved highly specialized biosonar systems to detect flying prey insects by virtue of unique Doppler signatures that are generated by the insect's wing beat. Since the Doppler shifts concerned are very small, this sensory feat requires a well-integrated suit of evolutionary specializations that include sonar signal design, cochlear filtering, representations all through the auditory system, and even adaptive behavioral control of the emi...

Causes of Ultrasound Doppler Twinkling Artifact

Ultrasound Doppler twinkling artifact is analyzed. It usually appears as a frequent color alteration in the region of hyperechoic objects. Its noiselike spectrum can also be seen in spectral Doppler mode. Physicians use twinkling artifact as a clinical sign for kidney-stone and soft-tissue calculi detection. The advantageous peculiarity of this study is that the experiments were conducted utilizing raw signals obtained from a custom ultrasonic machine and a specially developed phantom. The phantom contained specimens with known qualities, allowing for reproducible and predictable results. The experiments revealed evidence for two physical causes of twinkling artifact, which were associated with two unique Doppler signals. The research laid the foundation for the new reflected-signal model introduced and used throughout this paper.

Evidence for a Nimbostratus Uncinus in a Convectively Generated Mixed-Phase Stratiform Cloud Shield

Abstract The structure of a melting layer associated with a mesoconvective system is examined using a combination of in situ aircraft measurements and a unique Doppler radar operated by the U.S. Navy that has a range resolution as fine as 0.5 m. Interest in this case was motivated by ground-based all-sky camera images that captured the transient development of midlevel billow cloud structures within a precipitating trailing stratiform cloud shield associated with a passing deep convective system. A sequence of high-fidelity time–height radar measurements taken of this storm system reveal that the movement of the billow cloud structure over the radar site corresponded with abrupt transitions in the observed low-level precipitation structure. Of particular note is an observed transition from stratiform to more periodic and vertically slanted rain shaft structures that both radar and aircraft measurements indicate have the same temporal periodicity determined to arise visually between successive billow cloud bands. Doppler, balloon, and aircraft measurements reveal these transient bands are associated with a shallow circulation field that resides just above the melting level in a layer of moist neutral stability and strong negative vertical wind shear. The nature of these circulations and their impact on the evolving precipitation field are described in the context of known nimbostratus cloud types.

Ground-Based Rayleigh-Mie Doppler Lidar for Wind Measurements in the Middle Atmosphere

A unique Rayleigh-Mie Doppler wind lidar, measuring Doppler shift between the emitted and backscattered light using directdetection technique is deployed at Observatory of Haute Provence Southern France) and at Reunion island (tropical Indian Ocean). The instrument was shown capable of wind measurements between 5 and 50 km with accuracy better than 1 m/s up to 30 km. The system consists of a monomode Nd:Yag laser operating at 532 nm, three telescopes and a double-edge Fabry-Perot interferometer. The laser light is sent alternatively in the vertical as well as zonal and meridional directions at 40° from the zenith using a rotating mirror. The two components of the horizontal wind are obtained from the measurement of the Doppler shift of the return signal spectrally filtered by the Fabry-Perot etalon. After demonstration of the method in 1989 the measurements were used for studying stratospheric dynamics as well as for constructing wind climatology up to 50 km altitude. A new system, featuring a more compact design was installed at Maido observatory at Reunion Island (21° S). The design of the instrument, results of observations and comparison against GPS radiosondes are presented. Application of Doppler lidar for validation of the future ADM-Aeolus satellite mission is discussed as well.

Detection of Eye Blinking Using Doppler Sensor With Principal Component Analysis

We propose the detection of human eye blinking using a Doppler sensor. Eye blinking is one of the most common and convenient human activities that can be used as an input modality for computer devices, a simple communication methodology, and fatigue diagnostics. The reflected wave from the blinking eye has a unique Doppler signature. To investigate this signature, several measurements were performed with/without the noise caused by human movement when the sensor was placed near the eyes. We analyzed the Doppler signal in the joint time–frequency domain. It was found that the Doppler frequency produced by eye blinking is approximately 115 Hz. Furthermore, unconscious and conscious eye blinking exhibited different Doppler characteristics. In order to classify these characteristics, we employed a principal component analysis to extract the features. The truncated eigenvectors were multiplied with an image of eye blinking, and the resulting coefficients were used for classification. The proposed method successfully differentiated conscious eye blinking in the presence of noise from human motion in diverse scenarios.

Snowflake Size Spectra Retrieved from a UHF Vertical Profiler

Abstract This paper develops a technique for retrieving snowflake size distributions (SSDs) from a vertically pointing 915-MHz vertical profiler. Drop size distributions (DSDs) have been retrieved from 915-MHz profilers for several years using least squares minimization to determine the best-fit DSD to the observed Doppler spectra. This same premise is used to attempt the retrieval of SSDs. A nonlinear search, the Levenberg–Marquardt (LM) method, is used to search the physically realistic solution space and arrive at a best-fit SSD from the Doppler spectra of the profiler. The best fit is assumed to be the minimum of the squared difference of the log of the observed and modeled spectrum power over the precipitation portion of the spectrum. A snowflake video imager (SVI) disdrometer was collocated with the profiler and provided surface estimates of the SSDs. The SVI also provided estimates of crystal type, which is critical in attempting to estimate the density–size relationship. A method to vary the density–size relationship during the event was developed as well. This was necessary to correctly scale the SVI SSDs for comparison to the profiler-estimated distributions. Five events were examined for this study, and good overall agreement was found between the profiler and SVI for the lowest profiler gate (225 m AGL). Vertical profiles of SSDs were also produced and appear to be physically reasonable. Uncertainty estimates using simulated Doppler spectra show that the retrieval uncertainties are larger than that for rainfall and can approach and exceed 100% for situations with large spectral broadening as a result of atmospheric turbulence. The larger uncertainties are attributed to the lack of unique Doppler spectra for quite different SSDs, resulting in a less well-behaved solution space than that of rainfall retrievals.

Human recognition by active and passive acoustic signatures

Recognition of different sensed objects is a problem that often appears in practice. One of the solutions is based on analysis of the signatures of the specific objects. This method was applied for the acoustic detection of walking humans. Human footsteps excite envelopes of broadband acoustic signals in the air due to periodic friction forces between the foot and the ground/floor. The repetition frequency of these envelopes is equal to the footstep rate and usually lies below 3 Hz. High frequencies in these envelopes allow detection and localization of a walker using a narrowband ultrasonic receiver with a high directivity pattern. Consequently, periodic low frequency human motion results in passive ultrasonic detection using this method. This motion has also unique Doppler signatures and is measured using ultrasonic sonar. Common analyses of passive and Doppler signatures allow the extraction of the specific cadence in human motion and recognition of a human while rejecting other moving or stationary ob...

Renal Vein and Inferior Vena Cava Tumor Thrombus: Presentation and Mapping of Venous Extension with Color Duplex Ultrasound

Introduction Renal cell carcinoma (RCC) has a unique tendency toward intravascular growth into the renal vein (RV), inferior vena cava (IVC), or even into the heart. To determine the operative approach and degree of surgical resection required, an accurate preoperative assessment of the extent of the tumor thrombus (TT) is mandatory. The purpose of this report is to describe the presentation of TT with color duplex ultrasound (CDU) and to report our initial experience in mapping the extent of vascular invasion in five patients. Methods Between January and November 2004, 5 patients with suspected RCC underwent a renal CDU examination. The presence and extent of TT by CDU was correlated with contrast enhanced computerized tomography (CT), magnetic resonance imaging (MRI) or surgical findings. Results Three men and two women were found to have a unilateral renal mass. The arterial supply to each tumor was conspicuous and consisted of prominent feeding arteries by color or power Doppler that circumscribed and penetrated the mass. TT was localized to the RV in one case and involved the RV and IVC in four. For two patients, the growth of TT into the IVC was limited and nonocclusive whereas in two others it was extensive and occlusive. In one case, TT invaded the IVC and the contralateral RV. By gray-scale imaging, TT appeared as an echogenic, heterogeneous mass that caused focal dilatation of the vein followed by rapid tapering. Interestingly, in three patients, low-resistance pulsatile flow could be recorded within the TT tissue itself. When compared with computed tomography, magnetic resonance imaging, or the operative findings, CDU agreed with the location and extent of TT in all 5 cases. Conclusion CDU appears to be an accurate technique for mapping the extent of TT in patients with RCC. Although this series is small, the unique gray scale and spectral Doppler characteristics of TT noted on CDU may be beneficial in distinguishing bland thrombus from TT.

The Unique Phase Doppler Particle Analyzer Application and Analysis of Solid Particle Flow in the Fluidized Bed Combustor (FBC) Cold Model

The hydrodynamic effects of varying operating parameters in the fluidized bed combustor (FBC) have been of great interest to the FBC design and manufacturing process. Some experiments to investigate the gas/particle flows in the gaseous fluidized bed were performed with the laser-based phase Doppler particle analyzer (PDPA). In the experiments, the PDPA was used to measure the vertical component of fluidizing particle velocity at one specific position point. The robust experimental design method was used to evaluate the experimental conditions and to analyze the experimental results. An empirical model for the particle velocity vertical component Vy with particle size (S) and fluidizing airflow rate (R) as variables was developed for the FBC cold model. From the model, it was found that vertical component Vy has a strong linear relationship with the fluidizing airflow rate (R), while particle size (S) has less linear relationship to Vy. It can also be seen that Vy increased when fluidizing airflow rate increased and Vy decreased when particle size increased.

Unique Doppler pattern of “obstruction alternans” of a St Jude prosthetic mitral valve

We present a case of a patient who was pregnant and had symptomatic, intermittent obstruction of her St Jude mitral prosthesis showing a very unique Doppler flow pattern suggesting impaired disk movement with every other cardiac cycle. Mechanism of this “obstruction alternans” is discussed.

Unique Doppler velocimetry findings in heart failure of a fetus with giant cardiac rhabdomyoma

AbstractHerein, we report a case showing unique Doppler velocimetry findings, just before intrauterine death, in the heart failure of a fetus with cardiac rhabdomyoma located in the interventricular septum. Specific blood flow of only the inferior vena cava was observed when acute fetal heart failure occurred.

Granulosa cell tumors of the ovary: do they have any unique ultrasonographic and color Doppler flow features?

The aim of this study was to describe the ultrasonographic and Doppler flow attributes of granulosa cell tumors (GCT) of the ovary and to compare these attributes to those of epithelial tumors of the ovary. Among 13,475 gynecological patients who were scanned in our ultrasound unit between 1992 and 1996, seven patients had GCT. The final diagnosis was confirmed, postoperatively, by pathologic examination and by applying the WHO classification. The ultrasonographic findings of the GCT patients were compared to those recorded in a second group of 29 patients who had been diagnosed with epithelial tumor of the ovary. The sonographic appearance of GCT of the ovary was semi-solid and the endometrium was thick in six of the seven patients. Doppler flow studies of vessels within or in the contour of the lesions showed the resistive index (RI) to be 0.448 +/- 0.018. The epithelial tumors had a similar appearance and flow pattern except for the presence of ascites in one-third of the patients. Ultrasound scanning, including color Doppler flow, did not contribute data that could assist in differentiating between GCT and epithelial tumors of the ovary.

Neural network analysis of Doppler ultrasound blood flow signals: A pilot study

It has been hypothesised that each artery in the human body has its own characteristic “signature”—a unique Doppler flow profile which can identify the artery and which may also be modified by the presence of disease. To test this hypothesis an artificial neural network (ANN) was trained to recognise three groups of maximum frequency envelopes derived from Doppler ultrasound spectrograms; these were the common carotid, common femoral and popliteal arteries. Data were collected from 24 subjects known to have no significant atheromatous disease. The maximum frequency envelopes were used to create sets of training and testing vectors for a backpropagation ANN. The ANN demonstrated a high success rate for appropriate classification of the test vectors: 100% for the carotid; 92% for the femoral; and 96% for the popliteal artery. This work has demonstrated the ability of the ANN to differentiate accurately between different and similar flow profiles, outlining the potential of this technology to identify subtle changes induced by the onset of arterial disease within a specific vessel. It should be noted that the ANN not only models the maximum frequency envelope but also, unlike standard indices, makes a decision as to which artery the maximum frequency envelope belongs to, thus providing the potential to obviate human subjective classification.

Observations of turbulent boundary-layer interaction with a thunderstorm outflow ? A possible wake region energy source

Laboratory and numerical model simulations of turbulent circulations within the wake regions of thunderstorm outflows have been done with the assumption that there is no turbulence within the ambient airmass. Furthermore, many observational studies have used Doppler radar data that have been filtered so that turbulent structures are reduced in amplitude or eliminated altogether. This study presents unique Doppler radar observations of the collision of a roll-like boundary-layer circulation with a gust flow. The boundary-layer circulation is seen to interact with the circulation within the gust flow head and to reappear within the wake region. It is suggested that the ambient boundary layer may be an energy source for the generation and/or maintenance of turbulence in the wake region.

Very large phase velocities of non two‐stream, meter scale irregularities in the high latitude E region ionosphere

We present experimental evidence on a new category of meter wavelength radio auroral irregularities characterized by a unique Doppler spectrum signature. The new echo type has been identified with the Scandinavian Twin Auroral Radar Experiment radars which are capable of observing simultaneously full Doppler spectra from the same scattering volume along two widely different azimuths. The new echoes were seen only by the Finland radar which observes at large angles to the electrojet flow and at times when the Norway radar observed very stable type 1 echoes with phase velocities near the ion acoustic speed. The new spectrum, named type 5, is composed of three main frequency bands, two being symmetric about zero Doppler shift near ±450 m/s and a third always at very large phase velocities near 1000 m/s, this resulting to a characteristic asymmetry in the spectrum. The Doppler polarity of the large phase velocity component is always at negative shifts in the eastward electrojet and at positive shifts in the westward electrojet. These echoes, which are not strong and last from a few minutes to tens of minutes, were observed during strong but also moderate geomagnetic conditions but, apparently, always in the presence of large and stable electric fields. The evidence suggested that the new echoes cannot be due to direct generation by the two‐stream instability and, most likely, a secondary generation mechanism is involved. Although there are some similarities with 50 MHz type 4 spectral observations, type 5 echoes have unique characteristics which we believe are sufficient to justify their classification into a different echo category. We have no satisfactory theoretical explanation for the new echoes. That the fast moving irregularities have frequencies about two times the frequency of the simultaneously observed ion acoustic waves led us to suggest that a nonlinear resonant wave‐wave interaction process might be in operation under some appropriate conditions in the plasma.