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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.

Background Downstream remodeling of the spiral arteries (SpA) decreases utero-placental resistance drastically, allowing sustained and increased blood flow to the placenta under all circumstances. We systematically evaluated available reports to visualize adaptation of spiral arteries throughout pregnancy by ultra-sonographic measurements and evaluated when this process is completed. Methods A systematic review and meta-analysis of spiral artery flow (pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV)) was performed. English written articles were obtained from Pubmed, EMBASE and Cochrane Library and included articles were assessed on quality and risk of bias. Weighted means of Doppler indices were calculated using a random-effects model. Results In healthy pregnancies, PI and RI decreased from 0.80 (95% CI: 0.70–0.89) and 0.50 (95% CI: 0.47–0.54) in the first trimester to 0.50 (95% CI: 0.45–0.55, p p p = 0.752) and 0.36 (95% CI: 0.35–0.38, p = 0.037) in the third trimester, respectively. In parallel, PSV altered from 0.22 m/s (95% CI: 0.13–0.30 m/s) to 0.28 m/s (95% CI: 0.17–0.40 m/s, p = 0.377) and to 0.25 m/s (95% CI: 0.20–0.30 m/s, p = 0.560) in the three trimesters. In absence of second and third trimester Doppler data in complicated gestation, only a difference in PI was observed between complicated and healthy pregnancies during the first trimester (1.49 vs 0.80, p p = 0.349). Conclusions This review and meta-analysis concludes that an observed decrease of SpA PI and RI from the first towards the second trimester parallels the physiological trophoblast invasion converting SpA during early gestation, a process completed in the midst of the second trimester. Higher PI was found in SpA of complicated pregnancies compared to healthy pregnancies, possibly reflecting suboptimal utero-placental circulation. Longitudinal studies examining comprehensively the predictive value of spiral artery Doppler for complicated pregnancies are yet to be carried out.

Aim The relationship between body fluid composition measurements and echocardiographic tissue Doppler measurements before and after hemodialysis (HD) in end-stage renal disease is investigated. Materials and methods BCM (BCM-Fresenius Medical Care) Body Composition Monitor was used to measure the fluid status and body composition of patients by BIA method. TDE was performed before and after HD and the measurements were recorded. Results The mean age of the 72 patients was 53.7 +/- 17.2 years. There was a significant decrease in over hydration (OH) status, total body fluid (TBW), extracellular body fluid (ECW), intracellular body fluid (ICW), ECW/ICW ratio in patients after HD (p < 0.001, p0.001, p0.001, p0,001). A significant decrease in lateral, septal and tricuspid E' measurements and in E'/A' ratio was seen after HD (p: 0.012, p: 0.001,p < 0.001,p: 0.002, p0.001, p0,001). There was a significant difference in A' measurements from septal annulus in patients before and after HD (p: 0.001). A significant increase was observed in isovolemic contraction volume (IVCV) measurements from lateral, septal and tricuspid annulus in patients after HD (p < 0.001, p0.001, p: 0.012). A correlation was determined between the differences of lateral and tricuspid valve E' in patients before and after HD and the differences of ECW in patients before and after HD (p: 0.007r: 0.401,p: 0.017r: 0.358). Conclusion In this study; a correlation was determined between the acute decrease in OH amount and alteration in echocardiographic tissue Doppler parameters in patients after HD.

The optical navigation errors of Mars probe in the capture stage depend closely on which targets are selected to be observed in the Mars system. As for this problem, an integrated navigation scheme is proposed wherein the optical observation is aided by one-way Doppler measurements. The errors are then analyzed respectively for the optical observation and one-way Doppler measurements. The real-time calculating scheme which exploits the extended Kalman filter (EKF) framework is designed for the integrated navigation. The simulation tests demonstrate that the errors of optical navigation, which select the Mars moon as the observation target, are relatively smaller than those in the Mars-orientation optical navigation case. On one hand, the integrated navigation errors do not depend on the selecting pattern of optical observation targets. On the other hand, the integrated navigation errors are significantly reduced as compared with those in the optical-alone autonomous navigation mode.

Transthoracic echocardiography (TTE) is widely used as a pre-operative screening tool. It can provide extensive information about cardiac function and underlying pathology, which could influence decisions regarding surgery. This patient was referred for TTE as part of the pre-op screening, as he had a biological prosthetic aortic valve. This was a rare case where misleading TTE measurements inadvertently led to the patient being referred for transcatheter aortic valve replacement (TAVR), which delayed non-cardiac surgery. Routine pre-op TTE in a district hospital showed severely increased gradients compared to the previous year, so the patient was referred to a tertiary centre for TAVR. However peri-operative trans-oesophageal echocardiography (TOE) showed lower gradients and satisfactory valve area. The cause of high gradients at the time of pre-op screening was retrospectively attributed to profound anaemia present at the time. When the anaemia was corrected, the prosthetic valve gradients reduced to levels similar to the previous year. This case reiterates the fact that Echocardiographers should be familiar with haemodynamic factors that could affect the validity of Doppler measurements that use Bernoulli's equation and the continuity principle. This report also looks at how echocardiographers can mitigate the effects of non-valvar factors.

PURPOSE To investigate the impact of different breath-holding conditions on the results of renal artery Doppler ultrasonography (RADS). METHODS In 45 healthy volunteers, we performed RADS examination during breath-holding while breathing naturally and after a deep inspiration. We measured and compared peak systolic flow velocity (PSV), end diastolic velocity (EDV), and resistance index (RI) of the right (RRA) and left (LRA) renal artery, and PSV, EDV, RI, acceleration time and acceleration index (AI) of the right and left interlobar arteries. RESULTS The RRA and LRA PSV were, respectively, 76 ± 13 cm/s and 77 ± 15 cm/s under natural breathing and 93 ± 18 cm/s and 89 ± 24 cm/s after deep inspiration (P ≤ .001). The RRA and LRA EDV were also greater at deep inspiration (P

The aim of this study is assessment of importance of use of the modified myocardial performance index (Mod-MPI) for the evaluation of foetal cardiac function in foetuses of women with pregestational diabetes mellitus (PDM). In this study, data of 30 pregnant patients aged 18–45 years diagnosed with PDM and 30 pregnant women aged 18–45 years with normal pregnancy and their babies were evaluated. Foetal echocardiographic and doppler measurements, foetal biometric measurements, umbilical artery and ductus venosus pulsatility indexes were measured in both PDM and control groups. The Mod-MPI was significantly higher in foetuses of PDM women. Many influences especially cardiac and postpartum complications are observed in infants of PDM women. The Mod-MPI is a simple and useful method for assessing foetal ventricular function. Our study has shown that PDM is associated with foetal ventricular dysfunction.Impact statementWhat is already known on this subject? Although MPI is frequently used in routine clinical assessment of neonates, it is not used adequately in foetuses. Many influences especially cardiac and postpartum complications are observed in infants of PDM women. However, there are few studies focussed specifically on the assessment of foetal cardiac function in PDM. What do the results of this study add? MPI, which shows both diastolic and systolic functions is independent of ventricular anatomy and foetal heart rate, was found significantly higher in diabetic mother foetuses, can be said to be a valuable parameter in evaluating foetal cardiac functions globally. What are the implications of these findings for clinical practice and/or further research? Our study has shown that foetuses PDM are associated with foetal ventricular dysfunction. For this MPI measurement can be routinely performed at foetal cardiac measurements in foetuses of PDM mothers. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.

Background Pregnancies with reduced fetal movements (RFM) are at risk for poor neonatal outcomes and stillbirth. Aim To investigate whether Doppler measurements or angiogenic factors are good predictors of adverse neonatal outcomes in pregnancies with RFM. Methods This is a prospective pilot cohort study of 3243 women seeking care for RFM. Standard care was carried out in all cases. An extra Doppler examination was performed in 128 women to assess the flow in the middle cerebral artery, the umbilical artery, and the uterine artery. In 62/128 pregnancies, a maternal blood sample was obtained for angiogenic and antiangiogenic factors. The composite neonatal outcome of the study was one or more of the following factors: Apgar score

Background The clinical diagnosis of late Fetal Growth Restriction (FGR) involves the integration of Doppler ultrasound data and Fetal Heart Rate (FHR) monitoring through computer assisted computerized cardiotocography (cCTG). The aim of the study was to evaluate the diagnostic power of combined Doppler and cCTG parameters by contrasting late FGR –and healthy controls. Methods The study was conducted from January 2018 to May 2020. Only pregnant women who had the last Doppler measurement obtained within 1 week before delivery and cCTG performed within 24 h before delivery were included in the study. Two hundred forty-nine pregnant women fulfilling the inclusion criteria were enrolled in the study; 95 were confirmed as late FGR and 154 were included in the control group. Results Among the extracted cCTG parameters, Delta Index, Short Term Variability (STV), Long Term Variability (LTV), Acceleration and Deceleration Phase Rectified Slope (APRS, DPRS) values were lower in the late FGR participants compared to the control group. In the FGR cohort, Delta, STV, APRS, and DPRS were found different when stratifying by MCA_PI (MCA_PI 5th centile). STV and DPRS were the only parameters to be found different when stratifying by (UA_PI >95th centile or UA_PI The AUC of ROC curves were accurate for STV (0,70), Delta (0,68), APRS (0,65) and DPRS (0,71) when UA_PI values were > 95th centile while, the accuracy attributable to the prediction of MCA_PI was 0.76, 0.77, 0.73, and 0.76 for STV, Delta, APRS, and DPRS, respectively. An association of UA_PI>95th centile and MCA_PI Conclusions The results of this study show the contribution of advanced cCTG parameters and fetal Doppler to the identification of late FGR and the association of those parameters with the risk for NICU admission. Trial registration Retrospectively registered.

Background: Doppler ultrasonography is an essential part of evaluating the vascular haemodynamic variation seen within cirrhotic patients. Differences in haemodynamics exhibited in hepatic vasculature has been appeared in previous reports to associate with the clinical severity of cirrhosis. In any case, the degree of changes in Doppler ultrasound flow parameters in foreseeing the clinical severity of liver cirrhosis stays uncertain.Aim of Study: The purpose of this study was to evaluate the contribution of Doppler ultrasound of Hepatic Artery (HA) and Portal Vein (PV) with Child-Pugh (CP) score to assess the advancement of Hepatitis C Virus (HCV)-related liver cirrhosis.Patients and Methods: One hundred patients with HCV-related liver cirrhosis divided according to CP score were included. Doppler ultrasound variables including Portal Vein (PV) diameter, Maximum Portal Vein Velocity (MPVV), and resistance index of the hepatic artery (HARI) were measured.Results: There was significant association between the diameter of PV and the increase in CP score, which was statistically significant (p=0.000). A choice of 12mm as a cutoff point of PV diameter between CP, A and B revealed sensitivity of 96.9%, and specificity of 97.9%. The mean MPVV was statistically significantly higher with Child A (mean 17.1±1.6 cm/sec), compared to Child B and C (p= 0.000), and Child B (mean 14.1±1.9cm/sec) compared to Child C (mean 11.3±1.4cm/sec) (p=0.000). The mean HARI was statistically significantly lower with Child A and B (0.8cm/sec), compared to Child C (0.9cm/sec) (p=0.000). There was a strong negative correlation between HARI and MPVV which was statistically significant (p=0.000). There was a strong positive correlation between HARI and Child class and diameter of PV which was statistically significant (p=0.000).Conclusion: PV diameter is a useful predictor of advance-ment of liver cirrhosis. Doppler measurements of MPVV, and HARI are useful in differentiating patients with CP, A and B from C.

Purpose Continuous wave Doppler ultrasound is routinely used to detect cardiac valve stenoses. Vector flow imaging (VFI) is an angle-independent real-time ultrasound method that can quantify flow complexity. We aimed to evaluate if quantification of flow complexity could reliably assess valvular stenosis in pediatric patients. Materials and Methods Nine pediatric patients with echocardiographically confirmed valvular stenosis were included in the study. VFI and Doppler measurements were compared with transvalvular peak-to-peak pressure differences derived from invasive endovascular catheterization. Results Vector concentration correlated with the catheter measurements before intervention after exclusion of one outlier (r=−0.83, p=0.01), whereas the Doppler method did not (r=0.49, p=0.22). The change in vector concentration after intervention correlated strongly with the change in the measured catheter pressure difference (r=−0.86, p=0.003), while Doppler showed a tendency for a moderate correlation (r=0.63, p=0.07). Conclusion Transthoracic flow complexity quantification calculated from VFI data is feasible and may be useful for assessing valvular stenosis severity in pediatric patients.

Acute kidney injury (AKI) is a frequent and severe complication in cardiac surgery. Normal renal function is dependent on adequate renal perfusion, which may be altered in the perioperative period. Renal perfusion can be assessed with Doppler measurement. We aimed to determine the association between Doppler measurements of renal perfusion and the development of AKI. This was a prospective, observational study of 100 patients with ≥ one risk factor for postoperative AKI undergoing open-heart surgery. Doppler ultrasound examinations were performed before surgery and on the first and fourth postoperative day. AKI was defined according to the KDIGO criteria and subdivided into mild (KDIGO stage 1) and severe AKI (KDIGO stage 2 + 3). Thirty-three patients developed AKI, 25 developed mild and eight developed severe AKI. Abnormal renal venous flow pattern on the first postoperative day was significantly associated with the development of severe AKI (OR 8.54 (95% CI 1.01; 72.2), P = 0.046), as were portal pulsatility fraction (OR 1.07 (95% CI 1.02; 1.13), P = 0.005). Point-of-care Doppler ultrasound measurements of renal perfusion are associated with the development of AKI after cardiac surgery. Renal and portal Doppler ultrasonography can be used to identify patients at high risk or very low risk of AKI after cardiac surgery.

Antenatal imaging is crucial in the management of high-risk pregnancies. Accurate dating relies on acquisition of reliable and reproducible ultrasound images and measurements. Quality image acquisition is necessary for assessing fetal growth and performing Doppler measurements to help diagnose pregnancy complications, stratify risk, and guide management. Further research is needed to ascertain whether current methods for estimating fetal weight can be improved with 3-dimensional ultrasound or magnetic resonance imaging; optimize dating with late initiation of prenatal care; minimize under-diagnosis of fetal growth restriction; and identify the best strategies to make ultrasound more available in low-income and middle-income countries.

Background Planimetry of aortic stenosis can be performed when Doppler measurements are unavailable. We sought to evaluate if, as advised in guidelines, the geometric orifice area (GOA) threshold value of 1 cm² was concordant with the threshold of 1 cm² of the effective orifice area (EOA), and the factors influencing the contraction coefficient (EOA/GOA ratio). Methods In an in vitro mock circulatory system, we tested 6 degrees of AS severity (3 severe and 3 non-severe), and 3 levels of flow ( 250 ml/s). The EOA was calculated by Doppler-echocardiography, and the GOA was measured with dedicated software after camera acquisition. Results In all but the very low flow condition, an EOA of 1 cm² corresponded to a GOA of 1.2 cm². The contraction coefficient increased with both the flow and the stenosis severity. For very severe stenoses, the EOA and the GOA were interchangeable. Conclusion As observed in clinical studies, the GOA was larger than the EOA, and a GOA between 1 and 1.2 cm² should not discard the possibility of severe aortic stenosis.

To evaluate the intra-observer variability of the middle cerebral artery (MCA) and umbilical artery (UA) Doppler measurement taken under optimal conditions in term, uncomplicated pregnancies.A prospective study on uncomplicated singleton term pregnancies was performed. Multiple Doppler measurements were taken in the MCA and the UA by one examiner. Intra-rater agreement was calculated. Doppler indices were correlated to fetal biometric parameters and to gestational age.One hundred patients were recruited. MCA indices were found to have the highest strength of intra-rater/observer agreement (MCA PI measured at term is reproducible with a high ICC. MCA PI significantly decreases with advancing gestation at term. No correlation was found between Doppler measurements and time to delivery.

BACKGROUND Near-infrared spectroscopy measures cerebral saturation (Csat), although correlation with cerebral blood flow remains unclear in premature newborns at risk for intraventricular hemorrhage (IVH). OBJECTIVES Compare Doppler markers of anterior cerebral artery (ACA) flow with Csat obtained during head ultrasound (HUS). METHOD Newborns

The aim was to evaluate if medetomidine and dexmedetomidine affected arterial ovarian blood flow in dogs. The dogs were randomly assigned to two different groups. In Group 1, medetomidine (10 µg/kg) was administered intramuscularly and, in Group 2, dexmedetomidine (5 µg/kg) was used. After a preliminary exam, arterial blood pressure (BP) was measured and a duplex Doppler ultrasonographic examination of both ovarian arteries was performed. Twenty minutes after the administration of medetomidine or dexmedetomidine, BP and ovarian Doppler ultrasonography were repeated. High quality tracings of ovarian artery flow velocity were obtained in all dogs and Doppler parameters: Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV) and Resistive Index (RI) were measured before and after drug administration in the left (LO) and right (RO) ovaries. PSV and EDV values decreased significantly after drug administration (p &lt, 0.05) compared to the non-sedated values, but no differences were found between the LO and RO (p &gt, 0.05). The RI was not affected by drugs administration in neither of the groups studied (p &gt, 0.05). In conclusion, the administration of medetomidine or dexmedetomidine causes a decrease in blood flow velocity in the ovarian artery and may be a good choice to avoid excessive bleeding prior surgeries in which ovariectomy.

In previous works, a mobile application was developed using an unmodified commercial smartphone to recognize whole-body exercises. The working principle was based on the ultrasound Doppler sensing with the device built-in hardware. Applying such a lab environment trained model on realistic application variations causes a significant drop in performance, and thus decimate its applicability. The reason of the reduced performance can be manifold. It could be induced by the user, environment, and device variations in realistic scenarios. Such scenarios are often more complex and diverse, which can be challenging to anticipate in the initial training data. To study and overcome this issue, this paper presents a database with controlled and uncontrolled subsets of fitness exercises. We propose two concepts to utilize small adaption data to successfully improve model generalization in an uncontrolled environment, increasing the recognition accuracy by two to six folds compared to the baseline for different users.

A Multi-Constellation Software-Defined Receiver (MC-SDR) is designed and implemented to extract the Doppler measurements of Low Earth Orbit (LEO) satellite&rsquo, s downlink signals, such as Orbcomm, Iridium-Next, Globalstar, Starlink, OneWeb, SpaceX, etc. The Doppler positioning methods, as one of the main localization algorithms, need a highly accurate receiver design to track the Doppler as a measurement for Extended Kalman Filter (EKF)-based positioning. In this paper, the designed receiver has been used to acquire and track the Doppler shifts of two different kinds of LEO constellations. The extracted Doppler shifts of one Iridium-Next satellite as a burst-based simplex downlink signal and two Orbcomm satellites as continuous signals are considered. Also, with having the Two-Line Element (TLE) for each satellite, the position, and orbital elements of each satellite are known. Finally, the accuracy of the designed receiver is validated using an EKF-based stationary positioning algorithm with an adaptive measurement matrix. Satellite detection and Doppler tracking results are analyzed for each satellite. The positioning results for a stationary receiver showed an accuracy of about 132 m, which means 72% accuracy advancements compared to single constellation positioning.

Target tracking in passive multi-static radar (PMSR) with bistatic range and Doppler frequency measurements from multiple transmit-receive pairs is gaining increasing interest. For the data association problem in this scenario, the parallel architecture of a multi-sensor joint probabilistic data association (P-MSJPDA) filter has been significantly investigated. As an alternative architecture, the sequential MSJPDA (S-MSJPDA) is rarely discussed in PMSR. In this paper, we evaluate the behaviors of S-MSJPDA in PMSR target tracking with bistatic range and Doppler frequency measurements. A comprehensive comparison between the S-MSJPDA and the P-MSJPDA in PMSR is provided. It can be found from the analysis that S-MSJPDA outperforms its parallel counterpart in terms of computational efficiency, given an acceptable degradation in position accuracy. The S-MSJPDA is further applied to an experimental passive multi-static radar for aircrafts tracking. The real data results obtained are rather close to the true trajectories of the targets. This demonstrates that the S-MSJPDA has great potentials in PMSR target tracking.

International audience; Summary. Doppler ultrasound is an effective, useful and remarkably powerful tool in pediatric imaging. If possible, its use is always favored to avoid exposure to radiation or sedatives. By waveform spectrum analysis, Doppler ultrasound reveals information on blood flow and details on normal physiology and pathological processes undiscernible from gray-scale imaging alone. However, Doppler ultrasound remains underused, largely due to the difficult interpretation of changes in Doppler waveforms during childhood. This article provides a narrative review of the literature regarding the normative values and the physiological arterial changes through childhood according to age, weight or height, as well as frequent pathological arterial findings in children, classified by arterial territory.

With the recent push for a crewed Lunar mission to descend, land, and ascend from the Moon, there is a need for real-time position, velocity, and attitude knowledge of a Lunar spacecraft. Proposed approaches to achieve this include the use of weak-signals received from GPS and Deep Space Network (DSN)-aided measurements, but these require significant hardware development and active tracking from multiple ground stations. Additionally, these solutions may be unavailable during close approach and landing. This paper extends the previously published relative Doppler-based positioning scheme (Law of Cosines – LOC) and an absolute Doppler-based scheme (Conic Doppler Localization – CDL) with the aid of range measurements, an inertial measurement unit (IMU), and a star tracker to create the Doppler Based Autonomous Navigation (DBAN) architecture. DBAN allows for real-time, autonomous positioning with as few as one Lunar orbiter and a reference station on the surface of the Moon. LOC is a relative navigation architecture that converts Doppler measurements into Doppler-based range measurements with the aid of a reference station and at least one satellite. In addition, CDL is an absolute navigation architecture that converts Doppler measurements into conic sections for angle-based positioning. These architectures allow for localization with solely Doppler measurements that can be made using existing hardware, with significant performance improvements when including range measurements. However, the existing drawback with these architectures is that they require a static user; they can be biased through the Doppler shift produced by a moving user. With the aid of range measurements, an IMU, a star tracker, and a filter, DBAN can correct these biases and provide continuous Doppler-based navigation. In this analysis, the Lunar Gateway and the Lunar Relay Satellite (LRS) were used with a pre-existing reference station located on the south pole of the Moon to localize a user during orbit, descent, and landing. A surface constraint assumption was optionally implemented using the knowledge of the altitude of the user as a constraint. Satellite ephemeris, velocity, and external and internal measurement errors were modeled as Gaussian variables and embedded in Monte Carlo simulations to increase fidelity. An Extended Kalman Filter (EKF) was used due to the non-linear effects during intervals of high user dynamics. With DBAN, the positioning accuracy after more than 20 hours of integration approached 80 m at landing with a maximum error of about 800 m during a period of no external measurements and high dynamics (during low Lunar orbit). This was a significant improvement from directly filtering the range and Doppler measurements or from only dead reckoning. Just as with position, velocity error also increased with user dynamics, reaching a maximum of around 1 m/s with around 20 cm/s of error at landing. Finally, attitude error ranged from 1–2 arcseconds throughout the entire trajectory. Ultimately, the DBAN architecture can provide real-time position, velocity, and attitude knowledge with a minimal navigation infrastructure. DBAN can enable autonomous navigation for future crewed and uncrewed missions on other planets.

Objectives Echocardiography is used to quantitatively characterize cardiovascular function in fetuses with cardiac abnormalities and inform decisions for fetal or perinatal interventions. It is clinically important to understand the reproducibility of these measures, particularly between testers. While studies have reported intra-observer variability and inter-observer variability, little is known about test-retest variability for these measures. We hypothesized that even in a high volume echocardiography laboratory, quantitative measurements will demonstrate higher test-retest variability compared with inter-observer variability and intra-observer variability of the same measurements. Methods Prospective study of uncomplicated, singleton pregnancies to evaluate fetal measures of cardiovascular function obtained by echocardiography. One sonographer obtained predefined variables, and then, a second sonographer obtained the same variables 15 minutes after the first sonographer. Separate data acquisitions were obtained by the two sonographers to evaluate test-retest variability. Intra-observer variability and inter-observer variability were also evaluated. Results Thirty fetuses between 17- and 36-week gestation were enrolled. Time-based variables had the best intra-observer agreement and inter-observer agreement (1.2%-7.4%), while 2D (7.5%-10%), M-mode (4.9%-10.1%), and velocity-time integral (VTI; 2.6%-13.8%) measurements had poorer agreement. For all variables, test-retest agreement was worse (3%-32.1%), particularly for measurement of myocardial performance index (MPI; 19.7%-21.1%), cardiac output estimation (27.2%-27.9%), and VTI-based indices (14.7%-32.1%). Conclusions In a laboratory highly experienced in quantitative fetal echocardiography, intra-observer agreement and inter-observer agreement are good for most quantitative parameters. However, test-retest agreement is fair or poor for several variables, notably the MPI, cardiac output estimation, and VTI-based indices. Understanding how these measures vary between separate acquisitions is important for clinical interpretation and decision making.

Background The Doppler is thought to be more comfortable and effective compared to the fetoscope for assessing the fetal heart rate (FHR) during labor. However, in a rural Tanzanian hospital, midwives who had easy access to both devices mostly used fetoscope. This study explored midwives’ perception of factors influencing their preference for using either a Pinard fetoscope or a FreePlay wind-up Doppler for intermittent FHR monitoring. Methods Midwives who had worked for at least 6 months in the labor ward were recruited. Focus group discussion (FGD) was used to collect data. Five FGDs were conducted between December 2015 and February 2016. Qualitative content analysis was employed using NVivo 11.0. Results Three main themes emerged as factors perceived by midwives as influencing their preference; 1) Sufficient training and experience with using a device; Midwives had been using fetoscopes since their midwifery training, and they had vast experience using it. The Doppler was recently introduced in the maternity ward, and midwives had insufficient training in how to use it. 2) Ability of the device to produce reliable measurements; Using a fetoscope, one must listen for the heartbeat, count using a watch, and calculate, the Doppler provides both a display and sound of the FHR. Fetoscope measurements are prone to human errors, and Doppler measurements are prone to instrumental errors. 3) Convenience of use and comfort of a device; Fetoscopes do not need charging, and while it is possible to “personalize/hide” the measurements, and may be painful for mothers. Dopplers need charging and do not cause pain, but provide limited privacy. Conclusion Midwives’ preferences of FHR monitoring devices are influenced by the level of device training, experience with using a device, reliable measurements, and convenience and comfort during use. Fetoscopes and Dopplers should be equally available during midwifery training and in clinical practice. Electronic supplementary material The online version of this article (10.1186/s12884-018-1736-y) contains supplementary material, which is available to authorized users.

AIM Two-dimensional, transthoracic echocardiography does not account for the noncircular anatomy of the left ventricular outflow tract (LVOT) and may therefore underestimate LVOT area. Fusion of computed tomography (CT)-derived LVOT area and Doppler-derived flow data has been proposed to improve assessment of aortic valve area (AVA) and classification of aortic stenosis severity. For hemodynamic reasons, effective AVA has to be smaller than anatomic AVA. The aim of the study was to test the "fusion approach" by comparing effective CT-derived AVA with anatomic AVA from CT planimetry. METHODS AND RESULTS Data of 244 consecutive patients (mean age 81 ± 5 years, 61% female) with aortic stenosis were retrospectively analyzed comparing effective AVA (calculated from the continuity equation using CT-LVOT and transthoracic Doppler measurements) with anatomic AVA based on CT planimetry. Substituting the LVOT area from transthoracic echocardiography (TTE) by the CT-LVOT resulted in an increase in AVA from 0.74 ± 0.15 to 0.92 ± 0.18cm² (P

To evaluate tricuspid annular plane systolic excursion (TAPSE) in dogs with myxomatous mitral valve disease (MMVD) with or without pulmonary hypertension (PH) and to study the correlations with clinical and echocardiographic parameters.The study population included 99 dogs with MMVD and tricuspid regurgitation.This is a prospective clinical study. All dogs received a transthoracic echocardiographic evaluation, including 2D, M-mode, echo-Doppler, and tissue Doppler measurements. The TAPSE was measured from the left apical four-chamber view and normalized for the effect of body weight (nTAPSE). The dogs were grouped according to the severity of MMVD (American College of Veterinary Internal Medicine guidelines) and presence/absence and severity of PH. Significant differences between TAPSE or nTAPSE and echocardiographic parameters were analyzed among the MMVD and PH severity groups. Correlations between TAPSE or nTAPSE and echocardiographic parameters were calculated.Tricuspid annular plane systolic excursion or nTAPSE were not significantly different among dogs of the MMVD or PH severity groups. Significant correlations were obtained between TAPSE and body weight, left ventricular and atrial dimensions, early diastolic septal and early diastolic and systolic tricuspid annulus velocity (p0.001); nTAPSE was significantly correlated with normalized end-diastolic left ventricular dimension and fractional shortening (p0.001).The results show that neither TAPSE nor nTAPSE are reduced in dogs with MMVD with or without PH. It remains unclear if the right ventricle function is not reduced or if a reduced right ventricle function is masked by the contraction of the left ventricle through ventricular interdependence.

Aim Doppler echocardiography has become the standard imaging modality for diastolic function and provides pathophysiological insight into systolic and diastolic heart failure. In this study, we aimed to obtain normal echocardiographic Doppler parameters of healthy Turkish population. Methods Among 31 collaborating institutions from all regions of Turkey, 1154 healthy volunteers were enrolled in this study. Predefined protocols were used for all participants during echocardiographic examination and The American Society of Echocardiography and European Association of Cardiovascular Imaging recommendations were used for echocardiographic Doppler measurements. Results A total of 967 healthy participants were enrolled in this study after applying exclusion criteria. Echocardiographic examination was obtained from all subjects following predefined protocols. Mitral E wave velocity andE/Aratio were higher in females and decreased progressively in advancing ages. E wave deceleration time and A wave velocity were increased with aging. Assessment of tissue Doppler velocities showed that left ventricular laterale ', septale ', and septals ' were higher in younger subjects and in females.E/e ' ratio was increased progressively with advancing decades. Right ventriculare ' ands ' were decreased buta ' was increased with increasing age. Septale ' lower than 8 cm/s was 1.9% in the fifth decade and 13.7% in ages older than 50 years. TheE/e ' ratio greater than 15 (and also 13) was not found. Conclusion This study, for the first time, provides echocardiographic reference ranges for normal cardiac Doppler data in healthy Turkish population which will be useful in routine clinical practice as well as in future clinical trials. WOS:000560812700001 2-s2.0-85089593434 PubMed: 32815581

This paper proposes a new approach for improving the ranging precision using adjustment algorithm with doppler measurements. As a data processing technique, the proposed approach requires no additional supports of specifically designed hardware or software, which mainly takes advantages of the accurate doppler measurements. Simulations have been conducted and convincible results have been obtained, which validates the effectiveness of the proposed approach. Results also show that weights for doppler measurements should be carefully treated in practice, which would significantly affect the precision and coherency.

Background: Intraparenchymal thyroid Doppler measurements might be considered a useful index of the thyroid status as well as micro-circulation elsewhere in the body among sickle cell disea...

This paper proposes a new approach for spin motion estimation for in-orbit spacecraft using doppler measurements of ground stations. The magnitude of the angular velocity vector is firstly estimated using the spectrum of the spin motion induced velocity, and its direction is estimated then using the adjustment algorithm. Simulations have been conducted for validation of the proposed approach, which demonstrates the effectiveness of the estimation.

Objective To investigate whether Doppler pulsatility indices (PIs) of the fetal circulation in cases of fetal growth restriction (FGR) are associated with the general movements (GMs) of the neonate after birth. Methods This was a prospective observational cohort study including pregnancies with FGR diagnosed between June 2012 and September 2014. A diagnosis of FGR was based on an abdominal circumference or estimated fetal weight Results Forty-eight FGR cases were included with a median gestational age at delivery of 35 (range, 26-40) weeks. UA-PI, MCA-PI and CPR correlated strongly (rho, -0.374 to 0.472; P Conclusion Fetal arterial Doppler measurements are associated with the quality of neonatal GMs 1 week after birth, but this association is no longer evident at 3months post-term. Brain sparing in particular is associated strongly with GMs of an abnormal quality. Copyright (C) 2016 ISUOG. Published by John Wiley & Sons Ltd.

The diagnosis of hypertrophic cardiomyopathy (HCM) is based on clinical, echocardiographic and in some cases genetic findings. However, prognostication remains limited except in the subset of patients with high-risk indicators for sudden cardiac death. Additional methods are needed for risk stratification and to guide clinical management in HCM. We reviewed the available data regarding natriuretic peptides and troponins in HCM. Plasma levels of natriuretic peptides, and to a lesser extent serum levels of troponins, correlate with established disease markers, including left ventricular thickness, symptom status, and left ventricular hemodynamics by Doppler measurements. As a reflection of left ventricular filling pressure, natriuretic peptides may provide an objective measure of the efficacy of a specific therapy. Both natriuretic peptides and troponins predict clinical risk in HCM independently of established risk factors, and their prognostic power is additive. Routine measurement of biomarker levels therefore may be useful in the clinical evaluation and management of patients with HCM.

The present study was designed to describe the Doppler measurements of hepatic venous blood flow in camels (Camelus dromedarius). A total number of 9 adult healthy camels underwent hepatic Doppler examinations on the right side between the 11th and 9th intercostal spaces. The splenic and cranial mesenteric veins showed turbulent blood flows at their fusion to form the main portal trunk. At porta hepatis, the main portal vein exhibited turbulent blood flows and the mean velocities ranged from 21 to 28 cm/sec. In contrast, the intrahepatic branches of portal veins revealed smooth laminar spectral patterns with low blood velocities ranged from 12 to 22 cm/sec. In addition, hepatic veins and caudal vena cava have laminar blood flows. In conclusion, as a non-invasive clinical tool, Doppler ultrasonography is a simple and easy applicable method for assessment of hepatic hemodynamics in camels (Camelus dromedaries). The present findings have the potential to serve as references for evaluating the health status of the liver from camels. Therefore; a further research study, including comparative evaluation of Doppler findings in camels with various hepatic diseases, may be required.

Objective To develop reference ranges for the ductus venosus (DV) and tricuspid valve (TV) waveforms at 11–14 weeks and define auditable standards to assess operator measurement performance. Materials and methods A single operator prospectively obtained quantitative measurements of a number of DV and TV Doppler indices to develop medians and 90% reference intervals (RIs). Measurement agreement studies between two experienced operators were also performed. The measurement bias of three additional operators was subsequently assessed using the newly defined auditable standards. Results Doppler measurements were obtained in 292 patients (DV) and 321 patients (TV). Reference ranges were constructed for DV pulsatility index for veins (PIV) which did not change over gestation (mean 1.06; 90% RI 0.86–1.23) and for the TV E–A ratio reference range which was positively correlated with gestation. Measurement agreement studies on 30 additional patients showed the within-operator agreement was almost perfect for DV PIV (ICC, intraclass correlation 0.82–0.86) and strong for TV E–A ratio (ICC 0.68–0.78) while the between-operator agreement was good for both DV PIV and TV E–A ratio measurements (ICC 0.46 for both). Discussion Development of local reference ranges enabled the definition of quantitative auditable standards that can be utilised in assessment of operator training and ongoing Doppler measurement quality assurance. Measurements of DV PIV and TV E–A ratio by experienced operators were found to be reproducible.

There are three well-established detecting methods for cycle slip error, which are: Doppler measurement method, Phase-Code differencing method, and Phase-Phase Differencing Method. The first method depends on the comparison between observables and the fact that Doppler measurements are immune to cycle slip error. This method is considered as the most precise method for cycle slip detecting, because it succeed in detecting and predicting the smallest cycle slip size (1 cycle) in case the local oscillator has low bias. The second method depends on the comparison between observables (phase and code) and the code measurements are immune to the cycle slip error. But this method can’t detect or predict cycle slip size smaller than 10 cycles, because the code measurements have high noise. The third method depends on the comparison between observables (phase 1 and phase 2) and the phases measurements that have low noise. But this method can’t detect or predict cycle slip size smaller than 5 cycles, because the ionospheric change might have a high variation. For enhancing the precision of the last two methods in detecting the smallest cycle slip which size reaches 1 cycle, a new algorithm was developed in this research to determine the change in the ionospheric values and the code bias from epoch to epoch. That is done by solving all observables equations by least square technique. This modification on these methods succeed in detecting and predicting cycle slips of size of 1 cycle.

A Doppler centroid $\boldsymbol{D}_{ c}$ model based on the generalized curvature ocean surface scattering model (generalized curvature model or GCM) is presented. Two key features are included in this model: a skewness-related phase coefficient based on empirical skewness coefficients of sea-surface-slope probability density function (pdf) for wind speed less than 10 m/s and effects from wave breaking for wind speed greater than 10 m/s. Simulated $\boldsymbol{D}_{\mathbf{c}}$ values are exclusively compared with the empirical geophysical Doppler model function named CDOP, for $\mathbf{hh}$ and $\mathbf{vv}$ polarizations, various wind conditions, and incidence angles. Good agreement is found overall between CDOP and simulated $\boldsymbol{D}_{\mathbf{c}}$ values. The overall bias for simulated $\boldsymbol{D}_{\mathbf{c-hh}}$ with and without skewness are 2.63 versus −0.51 Hz (14.6 versus −2.8 cm/s), respectively; overall standard deviations are 2.76 versus 3.53 Hz (15.3 versus 19.6 cm/s). For simulated $\boldsymbol{D}_{\mathbf{c-vv}}$ , overall bias values with and without skewness are −0.16 versus −2.52 Hz (−0.9 versus −14 cm/s); standard deviations are 3.56 versus 4.32 Hz (19.7 versus 24 cm/s). The overall bias for simulated $\boldsymbol{D}_{\mathbf{c-hh}}$ with and without the wave breaking component are −0.08 versus 0.12 Hz (−0.4 versus 0.7 cm/s), respectively; corresponding standard deviations are 3.32 versus 4.75 Hz (18.4 versus 26.3 cm/s). Bias values for simulated $\boldsymbol{D}_{\mathbf{c-vv}}$ with and without the wave breaking component are −1.83 versus −2.02 Hz (−10.2 versus −11.2 cm/s), with corresponding overall standard deviations of 3.43 versus 4.87 Hz (19 versus 27 cm/s). The largest deviation from CDOP, of about 18 Hz (0.99 m/s), is found in the upwind direction for a 26° incidence angle, 10-m/s wind speed, and $\mathbf{hh}$ polarization.

Objectives Ankle to brachial index after heavy load exercise is the most accurate way of diagnosing minor arterial lesions in athletes, such as endofibrosis. The reliability and practical aspects of ankle to brachial index measurements after heavy-load exercise have not been studied. The purpose of this study was to analyze the interest of oscillometric automatic vs. manual Doppler measurements, for the calculation of ankle to brachial index, after heavy-load exercise in athletes. Design Prospective single-center study. Methods Fifteen healthy trained athletes performed an incremental test twice. Ankle to brachial index measurements were performed at Rest, as soon as possible after exercise (Rec-0), and then started at the 3rd minute of recovery (Rec-3), by two operators using each one of the two ankle to brachial index measurement methods. Results Mean times for automatic vs. manual ankle to brachial availability were 99±18s vs. 113±25s ( p =0.005) and 44±25s vs. 53±12s ( p =0.001) respectively at Rec-0 and Rec-3. Ankle to brachial index values from the two methods were highly correlated ( r =0.89). Mean absolute differences of automatic vs. manual ankle to brachial values from test–retest were 0.04±0.05 vs. 0.08±0.08 ( p >0.05) and 0.07±0.05 vs. 0.09±0.10 ( p >0.05) at Rest and Rec-0. Conclusions Automatic method allows obtaining faster and simultaneously post-exercise ankle to brachial index measurement compare to the manual Doppler. This time issue does not result in a significant change in absolute ankle to brachial index values, nor in the absolute differences of these in test–retest. Nevertheless, the test–retest variability of post-exercise ankle to brachial index results seems smaller with the automatic than the manual method.

Systolic tissue Doppler measurements (s') have been used to measure the velocity in myocardial motion and are a valuable tool for evaluating the systolic function of the left and right ventricles. Digestion of food is known to significantly alter hemodynamics and may therefore affect s'. The effect of food intake on s' parameters has not yet been studied. We assessed whether s' is affected by food intake. Nineteen healthy subjects aged 26·2 ± 4·2 years were investigated. s' was measured with pulsed tissue Doppler imaging in the right and left ventricles before the subjects ate a standardized meal and also 30 and 110 min after the meal. Three measurements were taken in each projection, and a mean value was calculated for each. s' increased significantly (P

Objective: In this study, we aimed to investigate the effects of fetal gender on umbilical artery and middle cerebral artery Doppler measurements.

Multi-static Doppler-shift has re-emerged recently in the target tracking literature along with passive sensing, especially for aircraft tracking. Tracking with multi-static Doppler only measurement requires efficient multi-sensor fusion approach and optimal sensor network configuration if possible. In this paper, we present a solution for multi-target tracking with Doppler only measurements using the multi-Bernoulli filter. To utilize Doppler measurements from multiple sensors, we investigate different multi-sensor fusion schemes and the sensor-target geometry analysis for optimal multi-static Doppler sensor network configuration. Sensor-target geometry analysis is presented to investigate optimal multi-static Doppler sensor network configuration. Numerical results verify that the proposed sequential Monte Carlo (SMC) multi-Bernoulli filter with sequential update scheme and using the carefully chosen network shows good performance. HighlightsThe multi-sensor multi-Bernoulli filter in different fusion schemes.Sensor-target geometry analysis of multi-static Doppler measurement for optimal network configuration.An efficient solution to tracking multiple targets from multi-static Doppler measurement by the multi-Bernoulli filter.

Intrauterine growth restriction (IUGR) is a serious pregnancy complication with short- and long-term health consequences. The mechanisms underlying this condition are not well understood. Animal models are the basis for understanding the causes of IUGR and for developing useful therapeutic strategies. Here, we aimed to ascertain the in utero growth of fetuses from NK (natural killer cells)/MC (mast cells)-deficient mothers that give birth to growth-restricted pups and to determine the time point at which IUGR starts. We used high frequency ultrasound imaging to follow-up fetal and placenta size and employed Doppler measurements to document blood supply to the fetus in females that were deficient for NK cells and MCs. In mice lacking NKs and MCs, we observed significantly reduced implantation sizes from mid gestation onward, which was further associated with smaller placentas. Additionally, NK/MC-deficiency was associated with absent and reversed end diastolic flow in umbilical arteries of the fetuses and an increased systolic/diastolic ratio as well as an elevated resistance index. Together, our results indicate that NKs/MCs promote blood flow, placental growth, and subsequent fetal development. The results of this study offer new insights as to how fetal growth is affected in vivo in NK/MC-deficient mice, whose pups are growth restricted at birth. The use of IUGR models and modern technologies enabling the in vivo follow-up of fetal development are important tools for understanding mechanisms behind pregnancy complications that in the future may lead to the development of effective therapies.

Background Stentless valves have long been considered the ideal valves in terms of hemodynamics. Recently, the Trifecta valve, a stented bioprosthesis with excellent fluid dynamic characteristics, has become available. The aim of the study was to compare the opening/closing pattern of the Freestyle stentless valve and the Trifecta valve with that of the native aortic valve. Methods A total of 12 patients with a Freestyle and 10 with a Trifecta valve were compared to normal native aortic valves in 12 control patients. Leaflet kinematics and hemodynamic parameters were obtained by echocardiographic M-mode and Doppler measurements. Results The control group displayed significantly longer Rapid Valve Opening Time (45 ± 7 ms) and Rapid Valve Closing Time (42 ± 9 ms) than Freestyle patients (Rapid Valve Opening Time: 32 ± 7 ms; Rapid Valve Closing Time: 31 ± 8 ms) and Trifecta patients (Rapid Valve Opening Time: 31 ± 7 ms; Rapid Valve Closing Time: 30 ± 8 ms) (P

This paper presents a solution to the problem of tracking multiple targets from multistatic Doppler measurements. To the best of our knowledge our solution is the first principled multitarget tracker for multistatic Doppler radar. The tracker is based on a closed form solution to the labeled multitarget Bayes filter, which can be implemented with linear complexity in the number of measurements. Numerical examples are presented to illustrate the effectiveness of the solution on simulated data.

This electronic document is aimed at the corrections of the received power through frequency modulated interrupted continuous wave radars. These corrections are important for the correct interpretation of the target characteristics. Power corrections, described in this paper, are modified for the measurement of the Doppler shifts. Doppler shifts are calculated by the using of the two dimensional fast Fourier transform. In practical part of this paper four types of windows were compared during calculation of the two dimensional spectra. We concluded that the correction coefficients should be determined for each window individually.

Stepped frequency radar technology, where the transmit waveform consists of a sequence of tones, has long been suggested for cost-effective and high-resolution applications. One recent use of this technology is in automotive application where, in addition to cost-effectiveness, a random stepped frequency (RSF) waveform can significantly reduce the interference between vehicles. In this paper we provide a generic framework for the range and Doppler measurements for multiple targets. We further suggest two possible methods for reducing the computational complexity of RSF waveforms processing, which is important for future automotive applications.

This paper presents a modified FastSLAM approach for the specific application of radar sensors using the Doppler information to increase the localization and map accuracy. The developed approach is based on the FastSLAM 2.0 algorithm. It is shown how the FastSLAM 2.0 approach can be significantly improved by taking the Doppler information into account. Therefore, the modelled, so-called expected Doppler, and the measured Doppler are compared for every detection. Both, simulations and experiments on real world data show the increase in accuracy of the modified FastSLAM approach by incorporating the Doppler measurements of automotive radar sensors. The proposed algorithm is compared to the state-of-the-art FastSLAM 2.0 algorithm and the vehicle odometry, whereas profiles of an Automotive Dynamic Motion Analyzer serve as the reference.