Analytical and Experimental Comparison of the Velocity of a Supersonic Projectile in the Soft Recovery System

In order to compare numerical analyses made by Song and Kim needed for predicting gas and water filling with experimental results we conducted an experiment to recover a test projectile (43.7 kg with a 155 mm diameter) at a velocity of 775 m/s in a soft recovery system with a length of 179 m using pressurized gas and filled water. The soft recovery system consisting of a series of pressure tubes had a diaphragm, piston, and water plug for filling the pressurized gas and water. We installed a continuous wave Doppler radar system for velocity measurements of the test projectile travelling in the pressure tubes and pressure transducers for measuring the pressure in the soft recovery system. Continuous wave Doppler radar has the advantage of achieving real-time measurements of the velocity of a test projectile. The velocity-time curve of the test projectile, measured using the continuous wave Doppler radar, and the pressure profile were compared with the numerical analysis results. The experiment results show good agreement with the numerical analysis results based on the one-dimensional Euler equation with an HLL Riemann solver.

The ability of continuous-wave Doppler ultrasound to detect fetal growth restriction

Background Fetal growth restriction (FGR), defined as a fetus failing to reach its genetic growth potential, remains poorly diagnosed antenatally. This study aimed to assess the ability of continuous-wave Doppler ultrasound of the umbilical artery (CWD-UmA) to detect FGR in healthy women with low-risk pregnancies. Methods and findings This prospective longitudinal descriptive cohort study enrolled infants born to low-risk mothers who were screened with CWD-UmA between 28–34 weeks’ gestation; the resistance index (RI) was classified as normal or abnormal. Infants were assessed at 6, 10, 14 weeks, and 6 months postnatally for anthropometric indicators and body composition using the deuterium dilution method to assess fat-free mass (FFM). Neonates in the abnormal RI group were compared with those in the normal RI group, and neonates classified as small-for-gestational age (SGA) were compared with appropriate-for-gestational age (AGA) neonates. Eighty-one term infants were included. Only 6 of 26 infants (23.1%) with an abnormal RI value would have been classified as SGA. The abnormal RI group had significantly reduced mean FFM and FFM-for-age Z-scores at 6, 10, 14 weeks, and 6 months compared with the normal RI group (P<0.015). The SGA group’s FFM did not show this consistent trend when compared to AGA FFM, being significantly different only at 6 months (P = 0.039). The main limitation of the study was the small sample size of the infant follow-up. Conclusions Abnormal RI obtained from CWD-UmA is able to detect FGR and is considered a useful addition to classifying the neonate only by SGA or AGA at birth.

Transthoracic Vector Flow Imaging in Pediatric Patients with Valvular Stenosis – A Proof of Concept Study

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.

Conventional echocardiography—basic principles

Echocardiography is an imaging technique that enables accurate assessment of cardiac structures and cardiac function. Conventional echocardiography involves different modalities—especially the M-mode, the 2D, and colour Doppler, as well as the pulsed-wave and continuous wave Doppler. The M-mode illustrates the reflections of a single sound beam plotted against time. 2D echocardiography enables the documentation of views, which represent characteristic sectional planes of the moving heart during one heart cycle. Colour Doppler echocardiography adds the information of blood flow to the 2D cineloop. Pulsed-wave Doppler is the acquisition of a local blood flow spectrum of a defined region represented by the dimension of the sample volume, whereas continuous wave Doppler displays the blood flow spectrum of all measured blood flow velocities along a straight line sound beam from its beginning to the end. The handling of the transducer has to be target-oriented, stable with respect to the imaging targets, and coordinated with respect to angle differences between the defined views to use all these modalities correctly to get optimal image quality of the cineloops and spectra. Thus, the focus of this chapter will be a mainly practically oriented description of scanning technique in transthoracic and transoesophageal echocardiography.

A novel, hands-free ultrasound patch for continuous monitoring of quantitative Doppler in the carotid artery

Quantitative Doppler ultrasound of the carotid artery has been proposed as an instantaneous surrogate for monitoring rapid changes in left ventricular output. Tracking immediate changes in the arterial Doppler spectrogram has value in acute care settings such as the emergency department, operating room and critical care units. We report a novel, hands-free, continuous-wave Doppler ultrasound patch that adheres to the neck and tracks Doppler blood flow metrics in the common carotid artery using an automated algorithm. String and blood-mimicking test objects demonstrated that changes in velocity were accurately measured using both manually and automatically traced Doppler velocity waveforms. In a small usability study with 22 volunteer users (17 clinical, 5 lay), all users were able to locate the carotid Doppler signal on a volunteer subject, and, in a subsequent survey, agreed that the device was easy to use. To illustrate potential clinical applications of the device, the Doppler ultrasound patch was used on a healthy volunteer undergoing a passive leg raise (PLR) as well as on a congestive heart failure patient at resting baseline. The wearable carotid Doppler patch holds promise because of its ease-of-use, velocity measurement accuracy, and ability to continuously record Doppler spectrograms over many cardiac and respiratory cycles.

Portable continuous wave Doppler ultrasound for primary healthcare in South Africa: can the EUnetHTA Core Model guide evaluation before technology adoption?

Background This study had a threefold aim: to test the value of stakeholder involvement in HTA to reduce evidence gaps and interpret findings; and to assess a medical device by applying the EUnetHTA Core Model (CM) in South Africa and thus ultimately provide a first overview of evidence for potential widespread adoption of the technology in a primary health care (PHC) setting. Used in primary healthcare setting for obstetric use, the technology under assessment is a low-cost continuous wave Doppler ultrasound (DUS). Methods The scoping of the assessment was defined by involving policy makers in selecting the domains and corresponding questions relevant to the ultrasound and its use. Additionally, hospital managers were invited to respond to dichotomous questions on the criteria for procurement. To substantiate evidence obtained from an initial literature review, different stakeholders were identified and consulted. The evidence generated fromall steps was used to populate the high-ranked assessment elements of the CM. Results The HTA on continuous-wave DUS incorporated the evidence on organizational, ethical, and social value of its use together with effectiveness, safety, and cost-effectiveness of the technology. The domains on “health problem” and “safety” had a higher rank than the rest of the nine domains. Unexplained fetal mortality is the largest single contributor to perinatal deaths in South Africa. Pregnant women in PHC setting were examined using a continuous-wave DUS, after their routine antenatal visit. The healthcare professionals interviewed, indicated the benefit in the use of continuous-wave DUS in the PHC setting and the need for training. Conclusions Collection and generation of evidence based on the HTA CM and the chosen decision criteria provided a generalized but structured guidance on the methodology. Several questions were not applicable for the technology and the context of its use and elimination of those that are inappropriate for the African context, resulted in a pragmatic solution. Engaging and consulting local stakeholders was imperative to understand the context, reduce evidence gaps, and address the uncertainties in the evidence, ultimately paving the way for technology adoption. Given the ongoing studies and the evolving evidence base, the potential of this technology should be reassessed.