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We propose a strategy for magnetic navigation of collective stem cell microrobots in blood environments under ultrasound Doppler imaging. The cell microrobots are fabricated through a coculture process of stem cells and iron microparticles, they have spheroidal structures and are actuated under external magnetic fields. The collective cell microrobots can be reversibly gathered and spread by adjusting the magnetic interaction, and these microrobots are able to exhibit collective motion in whole blood under rotating magnetic fields. Simulation results indicate that the induced blood flow around the collective pattern affects the motion of red blood cells, and experimental results show that Doppler signals are observed when emitting ultrasound waves to the microrobots. Due to the induced three-dimensional blood flow, Doppler signals can also be observed when the imaging plane is above the collective microrobots, which enables indirect localization when performing navigation on uneven surfaces. Moreover, collective patterns of different numbers of microrobots are formed in flowing conditions, and these collective biohybrid agents are actively navigated against flowing blood with a flow rate up to 4.5 mL/min (mean velocity: 5.97 mm/s). Our study investigates a strategy for pattern formation and navigation of collective microrobots under ultrasound Doppler imaging, demonstrating the integration of collective control approach and medical imaging holds great potential for real-time active delivery tasks.

This letter shows the first acquisition, Doppler tracking, and positioning results with Starlinks low Earth orbit (LEO satellite signals. A generalized likelihood ratio (GLR -based test is proposed to acquire Starlinks downlink signals. A Kalman filter (KF -based algorithm for tracking the Doppler frequency from the unknown Starlink signals is developed. Experimental results show Doppler tracking of six Starlink satellites, achieving a horizontal positioning error of 10 m.

The Third Sonic Boom Prediction Workshop was held on January 4–5, 2020, in conjunction with the AIAA SciTech conference. The workshop had 23 participants who represented 6 different countries and 1...

Objective: Carotid Doppler ultrasound has been a topic of recent interest, as it may be a promising noninvasive hemodynamic monitoring tool. In this study, the relation between carotid artery blood flow and invasive cardiac output (CO) was evaluated. Design: A prospective, observational study. Setting: A single-institution, tertiary referral hospital. Participants: Eighteen elective cardiac surgery patients. Interventions: CO was measured by calibrated pulse contour analysis. Simultaneously, carotid artery pulsed-wave Doppler measurements were obtained in the operating room in three clinical settings: after induction of anesthesia (T1), after a passive leg raise maneuverer (T2), and at the end of surgery (T3). Measurements and Main Results: Correlation and trending between carotid artery blood flow and invasive CO were evaluated. Furthermore, two Bland-Altman plots were constructed to evaluate the level of agreement between carotid artery-derived CO and invasive CO measurements. Carotid artery blood flow correlated moderately with invasive CO (ρ = 0.67, 95% confidence interval 0.56-0.76, p < 0.05). Concordance between the percentage change of carotid artery blood flow and invasive CO from T1 to T3 was 72%. The level of agreement between carotid artery-derived CO and invasive CO was ±2.29; ±2.57 L/min, with a bias of 0.1; –0.54 L/min, and mean error of 50% and 48%, for the two Bland-Altman analyses, respectively. Intraexamination precision was acceptable. Conclusions: In cardiac surgery patients, carotid artery blood flow correlated moderately with invasive CO measurements. However, the trending ability of carotid artery blood flow was poor, and carotid artery-derived CO tended not to be interchangeable with invasive CO.

Implantable Doppler devices are reliable adjuncts used for free flap monitoring. Occasionally, the probe/wire is not removed and remains in the soft tissues. The clinical safety of the retained probes and safety and compatibility with magnetic resonance imaging (MRI) have not been studied. We present a series of retained implantable Doppler probes examining clinic outcomes, safety and compatibility with MRI, and effect on MRI image quality.A retrospective review was conducted of patients who had an implantable Doppler device for free flap monitoring between July 2007 and August 2018. Routine post-operative imaging was reviewed for all patients to identify incidental findings of a retained probe. A subset of patients with retained implantable Doppler probes who underwent MRI was identified. Magnetic resonance images were reviewed to detect any degradation of image quality.A total of 323 patients who had an implantable Doppler device placed were reviewed 18 (5.6%) patients were identified with a retained probe and were included in this study. Mean age was 49 years with mean follow-up of 34.4 months. One potential device-related complication occurred in 1 (5.6%) patient. A total of 32 MRI scans were performed in 8 patients with retained devices, including 6 patients who underwent a total of 21 MRIs of the surgical site. There were no complications related to the MRI scans, and we found no significant degradation of image quality.Retained implantable Doppler probes were not associated with substantial adverse clinical outcomes nor affected MRI image quality of the surgical site.Les dispositifs de Doppler implantables sont fiables pour compléter la surveillance des lambeaux libres. Il arrive que la sonde ou le fil ne soit pas retiré et demeure dans les tissus mous. La sécurité clinique de ces sondes et leur compatibilité avec l’imagerie par résonance magnétique n’ont pas fait l’objet d’études. Les auteurs examinent les résultats cliniques d’une série de sondes de Doppler implantables laissées dans les tissus, de même que leur sécurité, leur compatibilité avec l’IRM et leur effet sur la qualité de l’image d’IRM.Les chercheurs ont effectué une analyse rétrospective des patients à qui on avait implanté un dispositif de Doppler pour surveiller un lambeau libre entre juillet 2007 et août 2018. Ils ont analysé l’imagerie postopératoire systématique de tous les patients pour trouver les observations fortuites de sonde laissée dans les tissus. Ils ont extrait un sous-groupe de patients qui présentaient une sonde de Doppler implantable laissée dans les tissus et ont examiné l’IRM pour déceler toute dégradation de la qualité de l’image.Sur un total de 323 patients à qui on avait implanté un dispositif de Doppler, 18 (5,6%) présentaient une sonde laissée dans les tissus et ont été inclus dans l’étude. D’un âge moyen de 49 ans, ils avaient reçu un suivi moyen de 34,4 mois. Un patient (5,6%) a subi une complication susceptible d’avoir été causée par le dispositif. Au total, les chercheurs ont effectué 32 IRM chez huit patients dont une partie du dispositif avait été laissée dans les tissus, y compris six patients qui ont subi un total de 21 IRM au foyer chirurgical. Ils n’ont constaté aucune complication liée à l’IRM et aucune dégradation importante de la qualité de l’image.Les sondes de Doppler implantable laissées dans les tissus n’entraînaient pas de résultats cliniques indésirables importants ni ne nuisaient à la qualité de l’IRM au foyer chirurgical.

Spectral Doppler ultrasound velocimetry involves systematic analysis of the spectrum of frequencies that constitute the Doppler signal. This chapter presents a general perspective on Doppler signal anlyses and describes the spectral Doppler ultrasound devices commercially available for clinical use. They include continuous-wave (CW) Doppler, pulsed-wave (PW) Doppler and duplex Doppler devices. Within the realm of obstetric usage, the application needs are diverse and require various choices of equipment. For example, fetal Doppler echocardiography requires advanced duplex ultrasound instrumentation, which combines the capabilities of high-resolution two-dimensional imaging with the PW Doppler mode and an acoustic power output appropriate for fetal application. For umbilical arterial hemodynamic assessment, simpler, substantially less expensive CW Doppler equipment with a spectral analyzer may be sufficient. It is essential therefore that one develop a basic understanding of the implementation of Doppler ultrasound technology.

Recently, the long coherent accumulation of radar signals becomes relevant in the analysis of Doppler portraits of targets. This interest is related to the desire of researchers to obtain more information about radar purposes. Detailed spectral analysis provides additional information on the parameters of the target and its maneuvers. Some studies published in special articles are being discussed. They analyzed the methods of high resolution for the spectrums of refl ected signals. It is possible to obtain detailed Doppler portraits. The development of the elemental base of the construction of radar devices contributes to the improvement of the processing processes of refl ected signals. The possibilities of highlighting useful signals of small objects against the background of refl ections from the sea surface are considered. The article provides the results of processing signals recorded by radars made by the technology of digital antenna array. The experimental results of the Doppler portraits used a long-term coherent accumulation of signals in the L and X bands. Doppler portraits of ISS signals, Boeing-type passenger aircraft, MiG-29 fi ghter, helicopter are analyzed. The possibility of compensating for changes in the signal phase, which occurs during the radial acceleration of the ISS is shown. This allowed to increase the of signal-to-noise ratio to 6 dВ. Experimental results allow you to observe the maneuver of the target, to measure the acceleration of individual elements of the structure and their evolution. It is proposed to use the method of assessing Doppler portraits in the «radial speed - radial acceleration» coordinate system. The method is useful to use in radar surveillance systems of space objects, in the development of methods for recognizing classes of radar targets and in determining the number of objects in the target group. The development of this method of analysis of signals in prospective RADAR with the digital antenna array will help to solve problems of optimal signal processing, identify the number of targets in the group and maneuver the target, recognize classes of targets by the number of brilliant points and cross-Size targets.

Pulsed wave (PW) Doppler ultrasound is routinely used in the clinic to assess blood flow. Our annual Doppler quality assurance tests revealed unexpectedly large errors in measurement of maximum velocity, exceeding our tolerance (error >20%), when using certain scanners with small Doppler sample volume dimensions. The aim of this study was to assess the dependence of maximum velocity estimates on PW Doppler sample volume size. A flow phantom with known steady flow was used to acquire maximum velocity estimates (maximum velocities of 24, 39 and 85 cm/s and sample volume range of 0.3–20 mm) with a variety of transducers and scanners in clinical use (51 probes from 4 manufacturers). Selected acoustic outputs were characterized using free-field hydrophone measurements. All maximum velocity estimates were within our tolerance for sample volume sizes ≥1.5 mm, although maximum velocity estimates typically increased with decreasing sample volume size. Errors exceeding our tolerance were commonly found for one manufacturer when using smaller sample volumes, resulting in up to 75% overestimation. Although intrinsic spectral broadening based on transit time considerations may help explain our findings, the sample volume dependence raises potential clinical concerns that users should be aware of and which manufacturers should consider addressing.

Doppler shift measurement using time standard stations as passive radar beacons is well-established as a means of estimating virtual ionospheric height. A community science experiment in distributed Doppler shift measurement was conducted in October 2019 using the time station WWV, on the event of that station's centennial. Participants were asked to collect Doppler shift data from the WWV 5-MHz carrier via the open-source software program fldigi. This experiment garnered participation from stations across the country, demonstrating considerable volunteer interest: 45 recordings of WWV's 5-MHz beacon were collected. The novel element of this study is the use of distributed low-fidelity sensors in this geophysical domain, and the robust participation of the amateur radio community was enabled by inexpensive and readily available instrumentation. In this letter, we present an initial correlation analysis of the resultant data and discuss its implications for future long-term distributed Doppler networks. The data collected are in good agreement and, when examined together, offer some insights into regional trends. Despite the variety of equipment used by the amateur community, this community science approach shows promise for addressing the problem of undersampling in the geospace system.

Background Impact on blood flow by double vein anastomosis in head and neck free flaps is unclear. We aimed to assess venous doppler loss of signal (LOS) rates of double vein system compared with a single vein system. Methods Consecutive free flaps with implanted venous flow couplers between 2015–2017 were included. LOS rates were compared between groups and with regard to flap type, defect site and recipient vein within double vein group. Results 92 double-vein (184 veins) and 48 single-vein flaps were included. LOS was similar in single- and double-vein flaps (11/48 (25%) versus 46/184 (25%), p = 0.765). Double veins had fewer flap takebacks compared with single vein (4.3% vs. 12.5%, p = 0.075). Common facial vein (CFV) anastomosis showed superior LOS rates compared with external jugular and CFV branches (p = 0.026). Conclusions Double vein anastomosis does not impact LOS rates, results in fewer flap takebacks, yet LOS rates depend on selected recipient vein.

High-frequency surface wave radar (HFSWR) can be effectively used to detect ships in the exclusive economic zone. However, the ship signal is concealed and interfered with various clutter and background noise in the Doppler spectrum. In this letter, a range-Doppler (RD) image-based novel ship detection algorithm is proposed by exploiting spatial-frequency information and a unique feature fusion based on the analysis of variance. The algorithm subsumes three successive stages: Stage I--the plausible region of interest is captured, Stage II--the features from different sources are fused into one generalized feature space, and Stage III--an extreme learning machine-based classifier is utilized to localize the ships. Experimental results on challenging HFSWR-RD datasets demonstrate that the proposed algorithm has a competitive performance over other ship detection algorithms.

With the development of the radar sensing technology, hand gesture sensing and recognition has attracted much attention. This letter adopts a frequency-modulated continuous wave (FMCW) radar to achieve short-range hand gesture sensing and recognition. Specifically, the range, Doppler, and angle parameters of hand gestures are measured by fast Fourier transformation (FFT) and multiple signal classification (MUSIC) algorithm, respectively. The mixup (MP) algorithm combined with augmentation (AU) algorithm using a weight factor is applied to expand the hand gesture data. Then, a complementary multidimensional feature fusion network-based hand gesture recognition (CMFF-HGR) is designed to extract the features and achieve HGR. Finally, a series of experiments are carried out to verify the effectiveness of the proposed approach, and the results show that the recognition accuracy is higher than the existing alternatives with low computational complexity.

In recent years, the stereo positioning technology based on multiview spaceborne synthetic aperture radar (SAR) images has been widely applied in digital surface model extraction. In this letter, problems of the existing methods based on the range-Doppler (RD) model in a multiview stereo solution are pointed out. A robust stereo positioning solution for multiview spaceborne SAR images based on the RD model is proposed. In the proposed method, the traditional RD model is normalized to reduce the model errors caused by the different scales of the range equation and Doppler equation. A weighting strategy is also proposed to improve the positioning accuracy. This strategy is useful for multiview stereo positioning when using images of different satellites with orbital data of different accuracies. The experiments based on GaoFen-3 and TerraSAR-X satellite data sets validate the effectiveness of the proposed method.

Materials with well-characterized acoustic properties are of great interest for the development of tissue-mimicking phantoms with designed (micro)vasculature networks. These represent a useful means for controlled in-vitro experiments to validate perfusion imaging methods such as Doppler and contrast-enhanced ultrasound (CEUS) imaging. In this work, acoustic properties of seven tissue-mimicking phantom materials at different concentrations of their compounds and five phantom case materials are characterized and compared at room temperature. The goal of this research is to determine the most suitable phantom and case material for ultrasound perfusion imaging experiments. The measurements show a wide range in speed of sound varying from 1057 to 1616 m/s, acoustic impedance varying from 1.09 to 1.71 × 106 kg/m2s, and attenuation coefficients varying from 0.1 to 22.18 dB/cm at frequencies varying from 1 MHz to 6 MHz for different phantom materials. The nonlinearity parameter B/A varies from 6.1 to 12.3 for most phantom materials. This work also reports the speed of sound, acoustic impedance and attenuation coefficient for case materials. According to our results, polyacrylamide (PAA) and polymethylpentene (TPX) are the optimal materials for phantoms and their cases, respectively. To demonstrate the performance of the optimal materials, we performed power Doppler ultrasound imaging of a perfusable phantom, and CEUS imaging of that phantom and a perfusion system. The obtained results can assist researchers in the selection of the most suited materials for in-vitro studies with ultrasound imaging.

Traditional range-instantaneous Doppler (RID) methods for maneuvering target imaging suffer from the problems of low resolution and poor noise suppression. We propose a new super-resolution inverse synthetic aperture radar (ISAR) imaging method based on deep-learning-assisted time-frequency analysis (TFA). Our deep neural network resembles the basic structure of a U-net with two additional convolutional-upsampling layers and l₁-norm loss function for super-resolution generation and noise suppression. The neural network is trained in advance to learn the mapping function between the low-resolution time-frequency spectrum inputs and their high-resolution references. Then, the linear TFA assisted by the pretrained network is integrated into the RID-based ISAR imaging system and is found to achieve sharply focused and denoised target image with super-resolution. Both the simulated and real radar data are used to evaluate the performance of the proposed method. Numerical experimental results demonstrate the superiority of the proposed ISAR imaging method over traditional ones.

X-ray spectra scattered at 90° by acrylic resin plates of various thicknesses are measured. The intensity and polarization of Compton-scattered X-rays are estimated from the spectra. As the thickness of the slab increases, the intensity increases but the polarization decreases. The optimal thickness for a polarized X-ray fluorescence spectrometer is determined, which provides both high intensity and high polarization.

Acoustic Doppler current profilers (ADCP) do not provide reliable water velocity measurements near the sea surface or bottom because acoustic sidelobe reflections from the boundary contaminate the Doppler velocity measurements. The apparent depth of the center of the sidelobe reflection is zsl = ha[1 − cos(θ)], where ha is the distance from the ADCP acoustic head to the sea surface and θ is the ADCP beam angle. However, sidelobe contamination extends one and a half ADCP bins below zsl as the range gating of the acoustic return causes overlap between adjacent ADCP bins. Consequently, the contaminated region z < zsl + 3Δz/2 is deeper than traditionally suggested, with a dependence on bin size Δz. Direct observations confirming both the center depth of the sidelobe reflection and the depth of contamination are presented for six bottom-mounted, upward-looking ADCPs. The sidelobe reflection is isolated by considering periods of weak wind stresses when the sea surface is smooth and there is nearly perfect reflection of the main beams away from the ADCP and hence little acoustic return from the main beams to the ADCP.

Summary Background Penile Doppler ultrasound (PDU) is suggested to be an alternative to blood gas analysis (BGA) from the corpora cavernosa in differentiating between high- and low-flow priapisms, with limited supportive evidence. Aim To compare penile Doppler ultrasound study and blood gas analysis in the diagnosis of priapism, through a systematic review of the literature. Methods Studies were identified by literature search of Medline, Scopus, Cochrane and ClinicalTrials.Gov. Studies were included if their participants had priapism evaluated by Penile Doppler ultrasound, and reported data on the blood gas analysis or pudendal artery angiography (PAA). Two authors independently extracted the articles using predetermined datasets, including indicators of quality. Outcomes Correlation of penile Doppler ultrasound with blood gas analysis and pudendal artery angiography. Results Twelve studies were included. Three studies compared Penile Doppler ultrasound to blood gas analysis and pudendal artery angiography. Penile Doppler ultrasound was used as adjunctive to blood gas analysis to differentiate low flow from high flow priapism, guidance for embolization, etiological diagnosis in three studies. Compared to pudendal artery angiography, penile Doppler ultrasound had a sensitivity of 40–100% and a specificity of 73%, to localize vascular injury and anatomical abnormalities (two studies). Penile Doppler ultrasound was also used for the follow-up after the treatment of priapism (two studies). No study reported an impact on functional results or a delay of management due to penile Doppler ultrasound use. Clinical Translation We reviewed evidence on penile Doppler ultrasound study in priapism. Penile Doppler ultrasound study performance was comparable to blood gas from corpus cavernosum. It is recommended to use doppler as an alternative diagnostic tool. Strengths & Limitations Our systematic review had limitations. Firstly, the number of cases in the included studies was small. Secondly, these studies were all retrospective. Lastly, few data were reported with regards to hemodynamic parameters of penile Doppler ultrasound, and the majority of studies did not describe these in detail. Conclusions Evidence supports that penile Doppler ultrasound is a reliable way for differentiating high-flow and low-flow priapism. We recommend penile Doppler ultrasound study as an alternative of blood gas analysis from corpus cavernosum, especially when the latter is not available. Level of evidence 3.

Azimuth multichannel synthetic aperture radar (SAR) working in the sliding spotlight mode can effectively achieve ultrahigh resolution and wide swath imaging. However, multichannel sliding spotlight SAR echoes with large pulse bandwidth and azimuth steering angle are difficult to reconstruct and process due to the large range frequency-dependent Doppler centroid varying frequency support. To resolve this problem, two azimuth preprocessing approaches both based on the range frequency-dependent deramping strategy are proposed in this article. In both approaches, echoes are handled by a range frequency-dependent azimuth deramping function at first, which assign the signal measurements to unambiguous Doppler frequencies. Afterward, in the first preprocessing approach, azimuth multichannel raw data can be reconstructed and combined before azimuth upsampling in the conventional two-step preprocessing technique. The other way to handle the deramped multichannel raw data is the modified full aperture azimuth multichannel sliding spotlight reconstruction approach, which embeds azimuth multichannel reconstruction into azimuth convolution between the deramped raw data and the selected range frequency-dependent azimuth deramping function. Furthermore, the azimuth data in the second approach should be resampled to obtain a uniform azimuth sampling interval. Computational complexity and effects on the following imaging algorithm of both approaches are analyzed and compared. Simulation results validate the proposed two azimuth multichannel preprocessing approaches.

Conventional beam-center approximation-based motion compensation (MOCO) algorithms fail to achieve an optimally focused image in the case of the high-resolution and high-frequency (HRHF) synthetic aperture radar (SAR) system. In this letter, a novel MOCO algorithm based on Doppler adjustment is developed with the ability to compensate the azimuth variant motion error. The change of the Doppler spectrum caused by the azimuth variant motion error is investigated and is eliminated by Doppler scaling. The proposed MOCO algorithm has dramatically improved precision when compared with the conventional MOCO methods in HRHF SAR imaging. Simulation experiments and extensive comparisons with other MOCO algorithms verify the effectiveness of the proposed algorithm.

Dynamic Myocardial Ultrasound Localization Angiography (MULA) is an ultrasound-based imaging modality destined to enhance the diagnosis and treatment monitoring of coronary pathologies. Current diagnosis methods of coronary artery disease focus on the observation of vessel narrowing in the coronary vasculature to assess the organ's condition. However, we would strongly benefit from mapping and measuring flow from intramyocardial arterioles and capillaries as they are the direct vehicle of the myocardium blood income. With the advent of ultrafast ultrasound scanners, imaging modalities based on the localization and tracking of injected microbubbles allow for the subwavelength resolution imaging of an organ's vasculature. Yet, the application of these vascular imaging modalities relies on an accumulation of cine loops of a region of interest undergoing no or minimal tissue motion. This work introduces the MULA framework that combines 1) the mapping of the dynamics of the microvascular flow using an ultrasound sequence triggered by the electrocardiogram with a 2) novel Lagrangian beamformer based on non-rigid motion registration algorithm to form images directly in the myocardium's material coordinates and thus correcting for the large myocardial motion and deformation. Specifically, we show that this framework enables the non-invasive imaging of the angioarchitecture and dynamics of intramyocardial flow in vessels as small as a few tens of microns in the rat's beating heart in vivo.

The aim of this study was to determine the intra- and inter-rater reliability of a new semi-automatic image analysis method for quantification of the shape of the Doppler signal and the intratendinous vascular resistance in patellar tendinopathy. Thirty athletes (27.4 y, standard deviation = 8.57 y) with patellar intratendinous vascularity were included in a cross-sectional study (42 tendons analyzed). The intratendinous blood flow was assessed with power Doppler and ImageJ (Version 1.50b, National Institutes of Health, Bethesda, MD, USA) quantification software over a manually selected region of interest. Two blinded observers performed the analysis of the Doppler signal (vascular resistance) and shape descriptors (number of signals, pixel intensity, area, perimeter, major diameter, minor diameter, circularity and solidity). The intraclass correlation coefficient (ICC) was calculated, and the Bland–Altman mean of differences (MoD) and 95% limits of agreement (LoA) were determined. Also, small real differences (SRDs) and the standard error of measurement (SEM) were calculated. Intra-rater reliability was at a maximum for area (ICC = 0.999, 95% confidence interval [CI] = 0.998–0.999) and at a minimum for solidity (ICC = 0.782, 95% CI: 0.682–0.853). The MoD and 95% LoA were very low, and the relative SRD and SEM were below 5.3% and 2%, respectively. The inter-rater reliability was the maximum for area (ICC = 0.993, 95% CI = 0.989–0.996) and the minimum for circularity (ICC = 0.73; 95% CI=0.611–0.817). The MoD and 95% LoA were low, with the SRD and SEM below 6% and 2.2%. The proposed quantitative method for studying the intratendinous Doppler signal in the patellar tendon is reliable and reproducible.

Objective: Ductus venosus blood flow velocity measurements are mandatory in many clinical indications. The evaluation of the flow is performed either by comparing results with general reference tables or by qualitative assessment of the “a” flow, in regard to reversed or absent flow in the spectral waveforms. The aim was to develop normal reference ranges in low-risk pregnancies in our population. Material and Methods: Measurements of flow velocities (S, v, D, a) and indices (pulsatility index for veins, peak velocity index for veins, a/S, S/a) were performed by a single experienced specialist in 1279 singleton, uncomplicated pregnancies between 11 and 40 weeks gestation. The absolute flow velocities (S, v, D, a, VmPeak) and indices were obtained from spectral waveforms using the equipment producer’s inbuilt system. The still images were stored in the picture archiving and communication system. Results: The predicted reference ranges of the ductus venosus blood flow velocities according to the gestational age are shown in tables and graphics. Predicted reference curves based on the 5th and 95th percentiles according to gestational week were plotted and are given in tables and figures. Conclusion: Normal reference ranges for absolute flow velocities and indices were calculated from a population of uncomplicated pregnancies attending a tertiary care center. The measurements were made from both the classic patterns of the waveforms and also considered variants of the spectral waveforms, which have recently been reported, for the first time in the medical literature.

To investigate fetal pulmonary hemodynamics in normal pregnancy using pulsed and color Doppler ultrasonography and to define Doppler reference ranges values in the whole fetal pulmonary circulation during different gestational ages.A prospective observational study was conducted to evaluate 190 healthy singleton pregnancies between 20 and 38 weeks of gestation, including 10 cases for each gestational age. The main pulmonary artery, right pulmonary artery, left pulmonary artery, ductus arteriosus and pulmonary veins waveforms were evaluated. The waveform profile was studied for each pulmonary vessel investigated. We calculated the normal distribution of data of 12 Doppler parameters, their values were expressed as 5th, 25th, 50th, 75th and 95th centile.We report several pulmonary hemodynamic changes with the progression of pregnancy. We focused on the hemodynamic values of the parameters most useful in clinical practice and that would better describe the hemodynamic events of this vascular district.This study reports a complete description of the fetal pulmonary hemodynamics at different gestational ages. Many hemodynamic parameters show a typical change during gestation. The reference ranges described in this study may help in situations where is indicated to evaluate the pulmonary hemodynamics and to identify healthy fetuses from those affected by pathological conditions related mainly to fetal cardiovascular anomalies and/or feto-maternal pathologic conditions.

Background: Doppler velocimetry is the best method of surveillance for fetal hypoxemia during pregnancy. Cerebroplacental ratio (CPR), has been suggested as a useful clinical simplification. It is believed that the CPR better predicts adverse perinatal outcomes than its individual components and better than conventional anthropometric models. Therefore, the aim of this study is to evaluate the significance of the cerebroplacental 10th centile threshold measured weekly from 36 weeks of gestation till delivery as a screening test for prediction of need for Cesarean section for intrapartum fetal compromise and the adverse neonatal outcome in women with normally grown fetuses and uncomplicated pregnancy. Methods: This study was carried out on 40 pregnant women uncomplicated, singleton pregnancy with appropriately grown fetuses on clinical assessment. The last Doppler indices including cerebroplacental ratio measurement obtained before labor was reported. CPR values below 1.1 were reported as abnormal. Various studies have variably defined the threshold of abnormal CPR ratio as

Background: The parotid glands are the largest salivary glands in humans and are frequently involved in various primary & systemic disease processes. The most common benign parotid gland tumor is pleomorphic adenoma. Around 20% of parotid tumors are malignant with most common parotid tumors being mucoepidermoid carcinoma and adenoid cystic carcinoma. Objective: To determine the diagnostic accuracy of pulsed and color Doppler for the evaluation of parotid gland cancer. Methods: It was a cross sectional study by design carried out in Department of Radiology and Department of Maxillofacial Surgery, Mayo Hospital – Lahore in a duration of three year. All the patients were examined with mind-ray 7.5 MHz linear transducer. There are three methods used collectively; Grey Scale, color Doppler and Pulsed Doppler in sonographic examination. Color Doppler and pulsed Doppler demonstrate number of blood vessels within the tumor, their Peak Systolic Velocity and Resistive Index respectively. Histo-pathological results were correlated post operatively with the data obtained from Doppler ultrasound. Data was analyzed using SPSS 23.0 Results: In this study, 192 patients were included .The mean age was 39.42 ± 11.93 years. 58.85% (112) were male patients and 41.15 %( 80) patients were females. The solid masses with regular margins were evaluated and the diagnostic accuracy of pulsed Doppler was found to be 87.5% taking histopathology as gold standard. Conclusion: This study shows pulsed Doppler to be more accurate tool for diagnosis of parotid gland tumor as compared to color Doppler taking histopathology as gold standard.

Smoothing process can effectively improve the accuracy of the Global Navigation Satellite System (GNSS) position estimation algorithm. In this study, a Doppler‐aided GNSS position estimation algorithm with a B‐spline smoothing strategy is proposed. B‐spline signal processing is used to smoothen the code measurements with Doppler measurements, which were selected because they are more robust and immune to cycle slips than carrier phase measurements. Next, the mathematical expressions of the smoothing process and position estimation are derived. The smoothing process is based on the structure of a digital filter, which is especially suitable for real‐time applications. The Cramer–Rao lower bound of the proposed algorithm is derived. Moreover, a complete implementation structure of the proposed algorithm is presented. The validity of the proposed algorithm is verified through scenario simulation in terms of static, kinematic, and adverse environments. The advantages of the proposed algorithm are demonstrated by comparison with existing algorithms.

As a new attempt to reject clutter in High Frequency Passive Bistatic Radar (HFPBR), the Cycle-Consistent Adversarial Network (CycleGAN)-based image domain clutter suppression algorithm works successfully by treating the clutter rejection problem as an image-to-image migration between the range-doppler spectrograms without and with clutter suppression. However, this algorithm also has some disadvantages such as too many calculation parameters, difficult model training and low clutter suppression rate. In this paper, a novel clutter suppression method based on an improved DenseNet CycleGAN (D-CycleGAN) is proposed. In this method, the ResNet block of the generator in the original CycleGAN network is replaced with the DenseNet block, to better extract clutter features. To better evaluate the clutter suppression performance of the deep learning network-based graph-relational method, a new index suitable for HF passive radar is introduced. Furthermore, the influence of the number of Dense blocks on the performance of the algorithm is also discussed. Finally, the performance of the proposed method is tested and verified on the measured data, compared with the traditional clutter suppression method and other popular image migration algorithms, such as Pix2pix. The results show that the D-CycleGAN-based method has better clutter suppression performance, stronger generalization ability, and better retained radar targets simultaneously.

BACKGROUND This pilot study aims at exploiting machine learning techniques to extract color Doppler ultrasound (CDUS) features and to build an artificial neural network (ANN) model based on these CDUS features for improving the diagnostic performance of thyroid cancer classification. METHODS A total of 674 patients with 712 thyroid nodules (TNs) (512 from internal dataset and 200 from external dataset) were randomly selected in this retrospective study. We used ANN to build a model (TDUS-Net) for classifying malignant and benign TNs using both the automatically extracted quantitative CDUS features (whole ratio, intranodular ratio, peripheral ratio, and number of vessels) and gray-scale ultrasound (US) features defined by the American College of Radiology (ACR) Thyroid Imaging Reporting and Data System (TI-RADS). Then, we compared the diagnostic performance of the model, the performance of another ANN model based on the gray-scale US features alone (TUS-Net), and that of radiologists. RESULTS The TDUS-Net (0.898, 95% CI: 0.868-0.922) achieved a higher area under the curve (AUC) than that of TUS-Net (0.881, 95% CI: 0.850-0.908) in the internal tests. Compared with radiologists, TDUS-Net (AUC: 0.925, 95% CI: 0.880-0.958) performed better than radiologists (AUC: 0.810, 95% CI: 0.749-0.862) in the external tests. CONCLUSIONS Applying a machine learning model by combining both gray-scale US features and CDUS features can achieve comparable or even higher performance than radiologists in classifying TNs.

Space‐time adaptive processing (STAP) methods can provide good clutter suppression potential in airborne radar systems. However, the performance of these methods is limited by the training samples' support in practical applications. To address this issue, a deep learning framework for STAP is developed. First, the clutter space‐time data and their exact clutter covariance matrices (CCMs) are simultaneously modelled via simulation, in which various non‐ideal factors such as aircraft crabbing, array errors, and internal clutter motion with all possible levels in practice are all considered. Then, a multi‐layer two‐dimensional convolutional neural network (CNN) is developed. In this CNN, low‐resolution angle‐Doppler profiles estimated by a few training samples are used for the input and the high‐resolution counterpart obtained by the exact CCMs are utilized for the labels. Once trained, the CNN can be used to predict the high‐resolution angle‐Doppler profile using a few measured data in near real time. The high‐resolution clutter spectrum can be further calculated using the space‐time steering dictionary and the above obtained profile. Finally, the CCM of the measured data can be constructed and the space‐time weight vector can also be achieved. Compared with recently developed sparsity‐based STAP methods, the performance of the proposed method is better and the computational load of it is far fewer, and therefore more suitable for real‐world implementation. The simulation results have demonstrated the superiority of the proposed method in both clutter suppression performance and computation efficiency.

Vascular dysfunctions can progress and lead to stroke and cardiovascular disease, especially in smokers. The presence of particular vascular changes according to sex has been described and they can be identified by the Doppler method. This study evaluated Doppler velocimetry parameters of the Ophthalmic Artery (OA) and the Middle Cerebral Artery (MCA) according to sex in smokers regarding a non-smoker group. This cross-sectional observational study included 178 subjects: 93 women and 85 men. Doppler parameters were assessed in OA and MCA. Student’s t-test was used, with p

In this article, a novel 2-D scanning synthetic aperture radar mode for high-resolution and wide-swath imaging is introduced. Instead of the interpulse progressive azimuth beam scanning used in Terrain Observation by Progressive Scans (TOPS) mode, the intrapulse continuous azimuth frequency scanning is employed in this mode. The same azimuth resolution as the multichannel TOPS mode can be obtained through this mode in the case of single channel transmitting and receiving. And the wide-swath imaging in range is still achieved through the cyclically elevation beam scanning from burst to burst. Moreover, the antenna aperture can be fully exploited for transmitting in this mode. Therefore, it will outperform the multichannel TOPS mode especially in the case of active array antenna. The signal model of this mode is derived. Based on the analysis of the characteristics of echo spectrum, the design criteria for this mode are developed, followed by a design example. Finally, an imaging algorithm for this mode is presented. Theoretical analysis and numerical simulations verify the effectiveness of the proposed design criteria and imaging algorithm.

In this paper, a dual-frequency continuous wave radar is proposed to achieve both localization and activity/ gesture recognition simultaneously. Specifically, features of different movements will be classified by the activity and gesture recognition network (AGRNet) which is a lightweight network based on MobileNet. The data that are recognized corresponding to walking will be used for moving target localization by comparing the phase difference in the Doppler domain between dual frequencies. In addition, a segmentation method is proposed to effectively segment continuous signals into individual time-periods corresponding to different motions by detecting the boundaries of signal changing. The experimental results show that the proposed method accomplishes the classification accuracy over 91% with 8 motion classes with a localization accuracy in the centimeter level.

OBJECTIVES The Doppler-based resistive index and semiquantitative evaluation of renal perfusion using color Doppler failed to discriminate renal recovery patterns in a recent study. The influence of operator experience on resistive index and semiquantitative evaluation of renal perfusion performances is however unknown. This study aimed at evaluating the performance of resistive index and semiquantitative evaluation of renal perfusion according to the operator experience to predict short-term renal prognosis in critically ill patients. DESIGN Preplanned ancillary analysis of a prospective multicenter cohort study. SETTING Seven ICUs. PATIENTS Unselected ICU patients. INTERVENTION Renal Doppler was performed at admission to the ICU. The diagnostic performance of resistive index and semiquantitative evaluation of renal perfusion to predict persistent acute kidney injury at day 3 was evaluated. MAIN RESULTS Overall, 371 patients were included, of whom 351 could be assessed for short-term renal recovery. Two thirds of the included patients had acute kidney injury (n = 233; 66.3%), of whom 136 had persistent acute kidney injury (58.4%). Overall performance in discriminating persistent acute kidney injury was however null with an area under the receiver operating characteristic curve less than 0.6 for both resistive index and semiquantitative evaluation of renal perfusion, and no difference across operator experience. A multivariate analysis using logistic regression with the center as a random effect adjusted on the operator experience showed no association between resistive index (odds ratio, 0.02 per international units (95% CI, 0.00-18.60 international units]) or semiquantitative evaluation of renal perfusion (odds ratio, 0.96 per international units [95% CI, 0.43-2.11 international units]) and persistent acute kidney injury. Similar results were obtained within subgroups of expert and nonexpert operators. CONCLUSIONS Doppler-based measurements performed by an expert or a nonexpert operator did not discriminate renal recovery patterns and neither modified the risk stratification of acute kidney injury persistence.

BACKGROUND Fetal cardiac magnetic resonance imaging (MRI) improves the diagnosis of congenital heart defects, but is sensitive to fetal motion due to long image acquisition time. This may be overcome with faster image acquisition with low resolution, followed by image enhancement to provide clinically useful images. PURPOSE To combine phase-encoding undersampling with super-resolution neural networks to achieve high-resolution fetal cine cardiac MR images with short acquisition time. STUDY TYPE Prospective. SUBJECTS Twenty-eight fetuses (gestational week 36 [interquartile range 33-38 weeks]). FIELD STRENGTH/SEQUENCE 1.5 T, balanced steady-state free precession (bSSFP) cine sequence. ASSESSMENT Images were acquired using fully sampled Doppler ultrasound-gated clinical bSSFP cine as reference, with equivalent cine sequences with decreased phase-encoding resolution (25%, 33%, and 50% of clinical standard). Two super-resolution methods based on convolutional neural networks were proposed and evaluated (phasrGAN and phasrresnet). Data were partitioned into training (36 cine slices), validation (3 cine slices), and test sets (67 cine slices) without overlap. Conventional reconstruction methods using bicubic interpolation and k-space zeropadding were used for comparison. Three blinded observers scored image quality between 1 and 10. STATISTICAL TESTS Image scores are reported as median [interquartile range] and were compared using Mann-Whitney's nonparametric test with P

The processing of high resolution spotlight synthetic aperture radar (SAR) data suffers from Doppler spectrum aliasing because of the limited pulse repetition frequency (PRF). A modified two-step a...

Rotary-wing unmanned aerial vehicles (UAVs) can be potentially used in wireless communications and therefore attract research from both academia and industry recently. However, most UAV air-to-ground channel models under 6 GHz have ignored the micro-Doppler effects due to the UAV’s propellers. In this letter, we reveal its principle and develop a method to estimate the micro-Doppler, including sounding waveform design, channel modeling, and Doppler frequency estimation. Our simulation results demonstrate that the estimated root-mean-squared error of micro-Doppler is smaller than 18.83 Hz for 963.09 Hz micro-Doppler frequency shift resulting from the rotation of the propellers in the rotary-wing UAV sub-6 GHz communications systems.

Consensus criteria for tremor classification in Parkinson’s disease (PD) patients are clinically important for automatically evaluating the PD rating scale. Wearable sensing tools with direct contact measurements can obtain physiological signals to monitor tremor symptoms. Then, machine learning algorithms (MLAs) can train the frequency-based parameters and motion features to accurately measure PD-related tremors. Noncontact measurement with customized computer information devices can also digitalize the digitized handwritten patterns with the bespoke movements that a hand makes for identifying tremor classes. However, wearable sensors need a set of multiple electrodes to be placed on a patient’s body to acquire biosignals, and the setup does not allow continuous measurement and limits the patient’s motion range. The handwritten patterns of noncontact-based methods need frequency-domain and linearization transformations. In addition, feature extraction methods and MLAs are limited in complex computations and adaptive applications. Hence, in this work, a noncontact measurement with an array X-band microwave (10 GHz) Doppler-based linear quantizer is designed to continuously measure upper limb movements for tremor class scaling. To overcome the complex computations, time-domain parametric features, including zero crossing (ZC), Willison amplitude (WAMP), and waveform length (WL) indexes, are used to extract the physical changes in the oscillation frequencies, amplitudes, and directions of tremor signals for scaling upper limb tremor (ULT) levels. In the experiments involving 10 subjects, the proposed noncontact bioradar sensor could quantify asymmetrical and irregular oscillations with a positive correlation (mean R2 > 0.85) between the three indexes (ZC, WAMP, WL) and various oscillation frequencies. The linear relationship quantizer could predict the ULT levels from 0 Hz to 8 Hz for PD patients (typical tremor frequency: 4–6 Hz). It could also map the three indexes into colored visual representation for computerized visual analysis.