Absolute retinal blood flow in healthy eyes and in eyes with retinal vein occlusion.

PURPOSE: To measure non-invasively retinal venous blood flow (RBF) in healthy subjects and patients with retinal venous occlusion (RVO). METHODS: The prototype named AO-LDV (Adaptive Optics Laser Doppler Velocimeter), which combines a new absolute laser Doppler velocimeter with an adaptive optics fundus camera (rtx1, Imagine Eyes®, Orsay, France), was studied for the measurement of absolute RBF as a function of retinal vessel diameters and simultaneous measurement of red blood cell velocity. RBF was measured in healthy subjects (n = 15) and patients with retinal venous occlusion (RVO, n = 6). We also evaluated two softwares for the measurement of retinal vessel diameters: software 1 (automatic vessel detection, profile analysis) and software 2 (based on the use of deep neural networks for semantic segmentation of vessels, using a M2u-Net architecture). RESULTS: Software 2 provided a higher rate of automatic retinal vessel measurement (99.5 % of 12,320 AO images) than software 1 (64.9 %) and wider measurements (75.5 ± 15.7 µm vs 70.9 ± 19.8 µm, p < 0.001). For healthy subjects (n = 15), all the retinal veins in one eye were measured to obtain the total RBF. In healthy subjects, the total RBF was 37.8 ± 6.8 µl/min. There was a significant linear correlation between retinal vessel diameter and maximal velocity (slope = 0.1016; p < 0.001; r2 = 0.8597) and a significant power curve correlation between retinal vessel diameter and blood flow (3.63 × 10-5 × D2.54; p < 0.001; r2 = 0.7287). No significant relationship was found between total RBF and systolic and diastolic blood pressure, ocular perfusion pressure, heart rate, or hematocrit. For RVO patients (n = 6), a significant decrease in RBF was noted in occluded veins (3.51 ± 2.25 µl/min) compared with the contralateral healthy eye (11.07 ± 4.53 µl/min). For occluded vessels, the slope between diameter and velocity was 0.0195 (p < 0.001; r2 = 0.6068) and the relation between diameter and flow was Q = 9.91 × 10-6 × D2.41 (p < 0.01; r2 = 0.2526). CONCLUSION: This AO-LDV prototype offers new opportunity to study RBF in humans and to evaluate treatment in retinal vein diseases.

Placental differences between severe fetal growth restriction and hypertensive disorders of pregnancy requiring early preterm delivery: morphometric analysis of the villous tree supported by artificial intelligence.

BACKGROUND: The great obstetrical syndromes of fetal growth restriction and hypertensive disorders of pregnancy can occur individually or be interrelated. Placental pathologic findings often overlap between these conditions, regardless of whether 1 or both diagnoses are present. Quantification of placental villous structures in each of these settings may identify distinct differences in developmental pathways. OBJECTIVE: This study aimed to determine how the quantity and surface area of placental villi and vessels differ between severe, early-onset fetal growth restriction with absent or reversed umbilical artery Doppler indices and hypertensive disorders of pregnancy or the 2 conditions combined among subjects with disease severity that warrant early preterm delivery. We hypothesized that the trajectories of placental morphogenesis diverge after a common initiating insult of deep defective placentation. Specifically, we postulated that only villi are affected in pregnancy-related hypertension, whereas both villous and vascular structures are proportionally diminished in severe fetal growth restriction with no additional effect when hypertension is concomitantly present. STUDY DESIGN: In this retrospective cohort study, paraffin-embedded placental tissue was obtained from 4 groups, namely (1) patients with severe fetal growth restriction with absent or reversed umbilical artery end-diastolic velocities and hypertensive disorders of pregnancy, (2) patients with severe fetal growth restriction with absent or reversed umbilical artery Doppler indices and no hypertension, (3) gestational age-matched, appropriately grown pregnancies with hypertensive disease, and (4) gestational age-matched, appropriately grown pregnancies without hypertension. Dual immunohistochemistry for cytokeratin-7 (trophoblast) and CD34 (endothelial cells) was performed, followed by artificial intelligence-driven morphometric analyses. The number of villi, total villous area, number of fetoplacental vessels, and total vascular area across villi within a uniform region of interest were quantified. Quantitative analyses of placental structures were modeled using linear regression. RESULTS: Placentas from pregnancies complicated by hypertensive disorders of pregnancy exhibited significantly fewer stem villi (-282 stem villi; 95% confidence interval, -467 to -98; P<.01), a smaller stem villous area (-4.3 mm2; 95% confidence interval, -7.3 to -1.2; P<.01), and fewer stem villous vessels (-4967 stem villous vessels; 95% confidence interval, -8501 to -1433; P<.01) with no difference in the total vascular area. In contrast, placental abnormalities in cases with severe growth restriction were limited to terminal villi with global decreases in the number of villi (-873 terminal villi; 95% confidence interval, -1501 to -246; P<.01), the villous area (-1.5 mm2; 95% confidence interval, -2.7 to -0.4; P<.01), the number of blood vessels (-5165 terminal villous vessels; 95% confidence interval, -8201 to -2128; P<.01), and the vascular area (-0.6 mm2; 95% confidence interval, -1.1 to -0.1; P=.02). The combination of hypertension and growth restriction had no additional effect beyond the individual impact of each state. CONCLUSION: Pregnancies complicated by hypertensive disorders of pregnancy exhibited defects in the stem villi only, whereas placental abnormalities in severely growth restricted pregnancies with absent or reversed umbilical artery end-diastolic velocities were limited to the terminal villi. There were no significant statistical interactions in the combination of growth restriction and hypertension, suggesting that distinct pathophysiological pathways downstream of the initial insult of defective placentation are involved in each entity and do not synergize to lead to more severe pathologic consequences. Delineating mechanisms that underly the divergence in placental development after a common inciting event of defective deep placentation may shed light on new targets for prevention or treatment.

Maternal rest improves growth in small-for-gestational-age fetuses (<10th percentile).

BACKGROUND: Optimal management of fetuses diagnosed as small for gestational age based on an estimated fetal weight of <10th percentile represents a major clinical problem. The standard approach is to increase fetal surveillance with serial biometry and antepartum testing to assess fetal well-being and timing of delivery. Observational studies have indicated that maternal rest in the left lateral position improves maternal cardiac output and uterine blood flow. However, maternal bed rest has not been recommended based on the results of a randomized clinical trial that showed that maternal rest does not improve fetal growth in small-for-gestational-age fetuses. This study was conducted to revisit this question. OBJECTIVE: This study aimed to determine whether maternal bed rest was associated with an increase in the fetal biometric parameters that reflect growth after the diagnosis of a small-for-gestational-age fetus. STUDY DESIGN: A retrospective study was conducted on fetuses who were diagnosed as small for gestational age because of an estimated fetal weight of <10th percentile for gestational age. The mothers were asked to rest in the left lateral recumbent position. Fetal biometry was performed 2 weeks after the diagnosis. All fetuses before entry into the study had a previous ultrasound that demonstrated an estimated fetal weight of >10th percentile. To assess the response to bed rest, the change in fetal biometric parameters (estimated fetal weight, head circumference, abdominal circumference, and femur length) after the recommendation of bed rest was computed for 2 periods: (1) before the diagnosis of a weight of <10th percentile vs at the time of diagnosis of a weight of <10th percentile and (2) at the time of diagnosis of a weight of <10th percentile vs 2 weeks after maternal bed rest. For repeated measures, proportions were compared using the McNemar test, and percentile values were compared using the Kruskal-Wallis test. A P value of <.05 was considered significant. To describe changes in the estimated fetal weight without bed rest, 2 control groups in which the mothers were not placed on bed rest after the diagnosis of a small-for-gestational-age fetus were included. RESULTS: A total of 265 fetuses were observed before and after maternal bed rest. The following were observed in this study: (1) after 2 weeks of maternal rest, 199 of 265 fetuses (75%) had a fetal weight of >10th percentile; (2) the median fetal weight percentile increased from 6.8 (interquartile range, 4.4-8.4) to 18.0 (interquartile range, 9.5-29.5) after 2 weeks of bed rest; (3) similar trends were noted for the head circumference, abdominal circumference, and femur length. In the groups of patients who were not asked to be on bed rest, a reassignment to a weight of >10th percentile at a follow-up examination only occurred in 7 of 37 patients (19%) in the Texas-Michigan group and 13 of 111 patients (12%) in the Colorado group compared with the bed rest group (199/265 [75%]) (P<.001). CONCLUSION: Patients who were prescribed 2 weeks of bed rest after the diagnosis of a fetal weight of <10th percentile had an increase in weight of >10th percentile in 199 of 265 fetuses (75%). This increase in fetal weight was significantly higher than that in the 2 control groups in which bed rest was not prescribed. This observation suggests that bed rest improves fetal growth in a subset of patients.

Doppler ultrasound of umbilical and middle cerebral artery in third trimester small-for-gestational age fetuses to decide on timing of delivery for suspected fetal growth restriction: A cohort with nested RCT (DRIGITAT).

OBJECTIVE: To assess the association of the umbilicocerebral ratio (UCR) with adverse perinatal outcome in late preterm small-for-gestational age (SGA) fetuses and to investigate the effect on perinatal outcomes of immediate delivery. DESIGN: Multicentre cohort study with nested randomised controlled trial (RCT). SETTING: Nineteen secondary and tertiary care centres. POPULATION: Singleton SGA pregnancies (estimated fetal weight [EFW] or fetal abdominal circumference [FAC] <10th centile) from 32 to 36+6 weeks. METHODS: Women were classified: (1) RCT-eligible: abnormal UCR twice consecutive and EFW below the 3rd centile at/or below 35 weeks or below the 10th centile at 36 weeks; (2) abnormal UCR once or intermittent; (3) never abnormal UCR. Consenting RCT-eligible patients were randomised for immediate delivery from 34 weeks or expectant management until 37 weeks. MAIN OUTCOME MEASURES: A composite adverse perinatal outcome (CAPO), defined as perinatal death, birth asphyxia or major neonatal morbidity. RESULTS: The cohort consisted of 690 women. The study was halted prematurely for low RCT-inclusion rates (n = 40). In the RCT-eligible group, gestational age at delivery, birthweight and birthweight multiple of the median (MoM) (0.66, 95% confidence interval [CI] 0.59-0.72) were significantly lower and the CAPO (n = 50, 44%, p < 0.05) was more frequent. Among patients randomised for immediate delivery there was a near-significant lower birthweight (p = 0.05) and higher CAPO (p = 0.07). EFW MoM, pre-eclampsia, gestational hypertension and Doppler classification were independently associated with the CAPO (area under the curve 0.71, 95% CI 0.67-0.76). CONCLUSIONS: Perinatal risk was effectively identified by low EFW MoM and UCR. Early delivery of SGA fetuses with an abnormal UCR at 34-36 weeks should only be performed in the context of clinical trials.

Abnormal Shape and Size of the Cardiac Ventricles Are Associated with a Higher Risk of Neonatal Death in Fetuses with Isolated Left Congenital Diaphragmatic Hernia.

INTRODUCTION: The objective of this study was to evaluate the association between fetal cardiac deformation analysis (CDA) and cardiac function with severe adverse perinatal outcomes in fetuses with isolated left congenital diaphragmatic hernia (CDH). METHODS: CDA in each ventricle (contractility, size, and shape), evaluated by speckle tracking and novel FetalHQ software, and markers of cardiac function (E/A ratios, pulmonary and aortic peak systolic velocities, and sigmoid annular valve diameters), were evaluated in fetuses with isolated left CDH. Two evaluations were performed: at referral (CDA and function) and within 3 weeks of delivery (CDA). Severe adverse neonatal outcomes were considered neonatal death (ND) or survival with CDH-associated pulmonary hypertension (CDH-PH). Differences and associations between CDA, cardiac function, and severe adverse outcomes were estimated. RESULTS: Fifty fetuses were included, and seventeen (34%) had severe adverse neonatal outcomes (11 ND and 6 survivors with CDH-PH). At first evaluation, the prevalence of a small left ventricle was 34% (17/50) with a higher prevalence among neonates presenting severe adverse outcomes (58.8 [10/17] vs. 21.2% [7/33]; p = 0.01; OR, 5.03 [1.4-19.1; p = 0.01]) and among those presenting with neonatal mortality (8/11 [72.7] vs. 9/39 [23.0%]; p = 0.03; OR, 8.9 [1.9-40.7; p = 0.005]). No differences in cardiac function or strain were noted between fetuses with or without severe adverse outcomes. Within 3 weeks of delivery, the prevalence of small left ventricle was higher (19/34; 55.8%) with a more globular shape (reduced transverse/longitudinal ratio). A globular right ventricle was significantly associated with ND or survival with CDH-PH (OR, 14.2 [1.5-138.3]; p = 0.02). CONCLUSION: Fetuses with isolated CDH at risk of perinatal death or survival with CDH-PH had a higher prevalence of a small left ventricle and abnormal shape of the right ventricle.

Imperatives of Mathematical Model of Arterial Blood Dynamics for Interpretation of Doppler Velocimetry: A Narrative Review.

Clinicians frequently study arterial Doppler velocimetric waveforms depicted by Doppler sonography of the kidneys, the heart, the brain, and the feto-maternal circulation to assess the well-being of the aforementioned vital organs. The waveform interpretation of the Doppler indices can be studied using a mathematical model. The developed models serve as teaching tools and for easy comprehension of the regulatory mechanism of the organs. It will also obtain accurate wall shear stress (WSS) and likely atherosclerotic sites can be predicted early. The aim of this review is to reveal the imperatives of mathematical models in the study of the physical interpretation of Doppler velocimetry. The models will explore sonographic Doppler velocimetry and computational fluid dynamics (CFD) in determining the segments of the arteries that are prone to the development of atheromatous plaque. It will be achieved by comparing and computing the measurement differences of the WSS. A thorough literature review was carried out between 1971 and 2021 on the mathematical modeling of blood dynamics and Doppler velocimetry of different blood vessels, across various electronic databases including NC AHEC Digital Library, PUBMED, ERIC, MEDLINE, Free Medical Journals, and EMBASE. The results of the literature search were presented using the PRISMA flow chat. The narrative review of the mathematical models of arterial blood dynamics is based on incompressible Navier-Stokes equations, the Windkessel model, and CFD. It was deduced that the blood flow velocity decreased with time across the varying frequency from 0.2Hz to 0.50Hz in the interlobar arterial channels. The review also revealed that adult humans' Doppler indices of the renal-interlobar artery agree with developed models of renal interlobar arterial blood dynamics. The mathematical model measurements of the great vessels matched the sonographic Doppler velocimetry with <15% variation. In our fast-paced world of epidemiological transition, the imperatives of mathematical modeling of arterial flow dynamics based on the Navier-Stokes equations to represent various physiologic and pathologic situations cannot be overstated. The practical consequences include the possibility of mathematical models to acquire precise WSS distribution and early detection of potential atherosclerotic sites during cardiovascular Doppler sonography.

Doppler velocimetry discordance between paired umbilical artery vessels and clinical implications in fetal growth restriction.

BACKGROUND: Studies revealing a discrepancy in umbilical artery Dopplers between the two umbilical arteries in normally-grown fetuses necessitates further evaluation of the paired umbilical arteries in the setting of fetal growth restriction as this is a critical component in the surveillance of this population. OBJECTIVE: Umbilical artery Doppler sampling in fetal growth restriction is typically assessed in 1 umbilical artery in a free loop of cord. Although discrepancies of >20% between the 2 umbilical arteries occur in 1 of 3 normal pregnancies, this has not been assessed in fetal growth restriction. Our objectives were to determine the frequency of discordant Doppler pulsatility indices between paired umbilical arteries in a fetal growth restriction cohort and to determine if sampling of 1 or both arteries alters surveillance or timing of delivery. STUDY DESIGN: A cohort of 425 growth-restricted fetuses between 25 and 39 weeks of gestation had umbilical artery Doppler pulsatility indices determined from both umbilical arteries in a midsegment of the cord to determine: (1) the discrepancy percentage between paired umbilical artery pulsatility indices and (2) the frequency of both arteries being normal, abnormal, or discordant (pulsatility index < and >95th percentile). To determine what sampling method increased the detection of an abnormal Doppler index, 3 sampling methods were compared: (1) average pulsatility index from both umbilical arteries, (2) pulsatility index from 1 umbilical artery chosen randomly, and (3) highest pulsatility index of the 2 umbilical arteries. RESULTS: The mean percentage difference between umbilical artery pulsatility indices was 11.7%, and in 15.8% of cases, it exceeded 20%. Both umbilical artery pulsatility indices were normal in 71.1% (302/425), abnormal in 12.2% (52/425), and discordant in 16.7% (71/425) of cases (P<.0001). Of the 3 sampling methods, the pulsatility index was abnormal in: (1) 19.2% (82/425) of cases when averaged from both umbilical arteries, (2) 22.1% (94/425) of cases when choosing 1 umbilical artery at random, and (3) 28.9% (123/425) of cases when the highest umbilical artery pulsatility index was used (P=.003). CONCLUSION: In this large fetal growth restriction cohort, the overall discrepancy between the 2 umbilical artery pulsatility indices was 11.7%. Among fetuses with at least 1 abnormal umbilical artery pulsatility index, 71 of 123 (57.7%) had 1 normal pulsatility index and 1 abnormal. Thus, the number of arteries sampled and the sampling method used may alter clinical decision-making, including frequency of surveillance and timing of delivery.

Clinical Opinion: The diagnosis and management of suspected fetal growth restriction: an evidence-based approach.

This study reviewed the literature about the diagnosis, antepartum surveillance, and time of delivery of fetuses suspected to be small for gestational age or growth restricted. Several guidelines have been issued by major professional organizations, including the International Society of Ultrasound in Obstetrics and Gynecology and the Society for Maternal-Fetal Medicine. The differences in recommendations, in particular about Doppler velocimetry of the ductus venosus and middle cerebral artery, have created confusion among clinicians, and this review has intended to clarify and highlight the available evidence that is pertinent to clinical management. A fetus who is small for gestational age is frequently defined as one with an estimated fetal weight of <10th percentile. This condition has been considered syndromic and has been frequently attributed to fetal growth restriction, a constitutionally small fetus, congenital infections, chromosomal abnormalities, or genetic conditions. Small for gestational age is not synonymous with fetal growth restriction, which is defined by deceleration of fetal growth determined by a change in fetal growth velocity. An abnormal umbilical artery Doppler pulsatility index reflects an increased impedance to flow in the umbilical circulation and is considered to be an indicator of placental disease. The combined finding of an estimated fetal weight of <10th percentile and abnormal umbilical artery Doppler velocimetry has been widely accepted as indicative of fetal growth restriction. Clinical studies have shown that the gestational age at diagnosis can be used to subclassify suspected fetal growth restriction into early and late, depending on whether the condition is diagnosed before or after 32 weeks of gestation. The early type is associated with umbilical artery Doppler abnormalities, whereas the late type is often associated with a low pulsatility index in the middle cerebral artery. A large randomized clinical trial indicated that in the context of early suspected fetal growth restriction, the combination of computerized cardiotocography and fetal ductus venosus Doppler improves outcomes, such that 95% of surviving infants have a normal neurodevelopmental outcome at 2 years of age. A low middle cerebral artery pulsatility index is associated with an adverse perinatal outcome in late fetal growth restriction; however, there is no evidence supporting its use to determine the time of delivery. Nonetheless, an abnormality in middle cerebral artery Doppler could be valuable to increase the surveillance of the fetus at risk. We propose that fetal size, growth rate, uteroplacental Doppler indices, cardiotocography, and maternal conditions (ie, hypertension) according to gestational age are important factors in optimizing the outcome of suspected fetal growth restriction.

Chronic hypertension and superimposed preeclampsia: screening and diagnosis.

Superimposed preeclampsia complicates about 20% of pregnancies in women with chronic hypertension and is associated with increased maternal and perinatal morbidity compared with preeclampsia alone. Distinguishing superimposed preeclampsia from chronic hypertension can be challenging because, in chronic hypertension, the traditional criteria for the diagnosis of preeclampsia, hypertension, and significant proteinuria can often predate the pregnancy. Furthermore, the prevalence of superimposed preeclampsia is unlikely to be uniformly distributed across this high-risk group but is related to the severity of preexisting endothelial dysfunction. This has led to interest in identifying biomarkers that could help in screening and diagnosis of superimposed preeclampsia and in the stratification of risk in women with chronic hypertension. Elevated levels of uric acid and suppression of other renal biomarkers, such as the renin-angiotensin aldosterone system, have been demonstrated in women with superimposed preeclampsia but perform only modestly in its prediction. In addition, central to the pathogenesis of preeclampsia is a tendency toward an antiangiogenic state thought to be triggered by an impaired placenta and, ultimately, contributing to the endothelial dysfunction pathognomonic of the disease. In the general obstetrical population, angiogenic factors, such as soluble fms-like tyrosine kinase-1 and placental growth factor, have shown promise in the prediction of preeclampsia. However, soluble fms-like tyrosine kinase-1 and placental growth factor are impaired in women with chronic hypertension irrespective of whether they develop superimposed preeclampsia. Therefore, the differences in levels are less discriminatory in the prediction of superimposed preeclampsia compared with the general obstetrical population. Alternative biomarkers to the angiogenic and renal factors include those of endothelial dysfunction. A characteristic of both preeclampsia and chronic hypertension is an exaggerated systemic inflammatory response causing or augmenting endothelial dysfunction. Thus, proinflammatory mediators, such as tumor necrosis factor-α, interleukin-6, cell adhesion molecules, and endothelin, have been investigated for their role in the screening and diagnosis of superimposed preeclampsia in women with chronic hypertension. To date, the existing limited evidence suggests that the differences between those who develop superimposed preeclampsia and those who do not are, as with angiogenic factors, also modest and not clinically useful for the stratification of women with chronic hypertension. Finally, pro-B-type natriuretic peptide is regarded as a sensitive marker of early cardiac dysfunction that, in women with chronic hypertension, may predate the pregnancy. Thus, it has been proposed that pro-B-type natriuretic peptide could give insight as to the ability of women with chronic hypertension to adapt to the hemodynamic requirements of pregnancy and, subsequently, their risk of developing superimposed preeclampsia. Although higher levels of pro-B-type natriuretic peptide have been demonstrated in women with superimposed preeclampsia compared with those without, current evidence suggests that pro-B-type natriuretic peptide is not a predictor for the disease. The objectives of this review are to, first, discuss the current criteria for the diagnosis of superimposed preeclampsia and, second, to summarize the evidence for these potential biomarkers that may assist in the diagnosis of superimposed preeclampsia.

Umbilical artery pulsatility index and half-peak systolic velocity in second- and third-trimester fetuses with trisomy 18 and 13.

OBJECTIVES: To analyze umbilical artery (UA) Doppler velocimetry and its possible role in placenta-mediated fetal growth restriction (FGR) in second- and third-trimester fetuses with trisomy 18 and 13. METHODS: UA pulsatility index (PI) and half-peak systolic velocity deceleration time (hPSV-DT) were measured in fetuses with trisomy 18 and 13. Correlation with gestational age, birthweight, and perinatal outcome was analyzed. RESULTS: A total of 80 measurements were taken from 33 fetuses with trisomy 18 and 19 with trisomy 13. Overall, there was a high prevalence of abnormal UA Doppler velocimetry. In fetuses with trisomy 18, 54% (27/50) of the UA PI values and 58% (29/50) of the UA hPSV-DT values were abnormal. In fetuses with trisomy 13, 80% (24/30) of the UA PI values and 87% (26/30) of the UA hPSV-DT values were abnormal. The prevalence of abnormal UA Doppler velocimetry increased with gestational age in both types of aneuploidy. However, this trend was only significant for trisomy 13 (p<0.05). All fetuses with trisomy 18 and 86% of fetuses with trisomy 13 were classified at birth as FGR. There were no perinatal survivors in this series. CONCLUSIONS: A high prevalence of abnormal UA Doppler velocimetry was found in second- and third-trimester fetuses with trisomy 18 and 13, which further increased with gestational age. These results may well correlate with alterations described previously in the placenta, suggesting placental insufficiency has an important role in the development of FGR in these autosomal aneuploid fetuses.

A Low-Cost, Low-Power Water Velocity Sensor Utilizing Acoustic Doppler Measurement.

Current commercial sensors to monitor water flow velocities are expensive, bulky, and require significant effort to install. Low-cost sensors open the possibility of monitoring storm and waste water systems at a much greater spatial and temporal resolution without prohibitive costs and resource investment. To aid in this, this work developed a low-cost, low-power velocity sensor based on acoustic Doppler velocimetry. The sensor, costing less than 50 USD is open-source, open-hardware, compact, and easily interfaceable to a wide range of data-logging systems. A freely available sensor design at this price point does not currently exist, and its novelty is in enabling high-resolution real-time monitoring schemes. The design is capable of measuring water velocities up to 1200 mm/s. The sensor is characterised and then verified in an in-field long-term test. Finally, the data from this test are then used to evaluate the performance of the sensor in a real-world scenario. The analysis concludes that the sensor is capable of effectively measuring water velocity.

Evaluation of cardiac sphericity index among intrauterine growth restriction and normal fetuses.

Foetal growth restriction (FGR) describes the pregnancy complications of pathological reduced foetal growth, leading to significant perinatal mortality and morbidity, and subsequent long-term cardiovascular outcomes. This prospective case-control study was performed on pregnant women referred to the hospitals of Tehran University of Medical Sciences in 2017-2019. All pregnant women underwent ultrasound scan and doppler sonography. FGR was defined as a sonographic estimation of foetal weight below the tenth percentile for a given gestational age. Cardiac sphericity index, including basal-apical length (BAL), transverse length (TL), global sphericity index (GSI), umbilical artery pulsatility index (PI), middle cerebral artery (MCA) PI and cerebroplacental ratio (CPR) were assessed. Mean gestational age in FGR and control groups were 233.90 ± 22.00 days and 229.00 ± 25.02 days, respectively. Foetal size index and estimated foetal weight in FGR foetuses were significantly lower than the control group (p < .05). BAL, TL and GSI were significantly affected by FGR (p = .0001, p = .018 and p = .0001, respectively). Abnormal GSI, MCA PI, umbilical artery PI and CPR were significantly more prevalent among FGR foetuses (p = .017, p = .0001, p = .0001 and p = .0001, respectively). Cardiac sphericity index, as well as uterine PI, MCA PI and CPR, were the determinants of FGR in foetuses with normal Doppler and abnormal GSI.IMPACT STATEMENTWhat is already known on this subject? Foetal growth restriction (FGR) describes the foetus that does not grow to its expected biological potential in utero, and is a relatively common complication of pregnancy. FGR is accosted with negative birth outcomes and long-term cardiovascular outcomes. One of the indicators of FGR is cardiac sphericity.What do the results of this study add? The findings of this study revealed that the cardiac sphericity index as well as umbilical PI, MCA PI and CPR ratio change in FGR foetuses.What are the implications of these findings for clinical practice and/or further research? It is recommended that more studies be performed to follow FGR foetuses longitudinally and evaluate the long-term cardiac abnormalities in infancy and childhood and compare it between FGR foetuses and normal foetuses.

Reconstruction of Velocity Curve in Long Stroke and High Dynamic Range Laser Interferometry.

To study the law that governs the complex movements of the mechanism in the process of automatic weapon operation, the velocity tracking test technology of photon Doppler velocimetry is introduced to accurately measure velocity, displacement and acceleration, on the condition that there are long displacement and rapid velocity change. In the traditional way, out of interference signal time-frequency (TF) transformation draws TF distribution, and then by modulus maxima frequency extraction, comes to the law of velocity change. Due to the influence resulting from the change of fundamental signal as well as that of light intensity signal in the test, based on the TF distribution obtained by TF transformation, the traditional modulus maxima frequency extraction can extract frequency signals, but they show abnormal sudden changes at some moments, making the velocity discontinuous, unsmooth and unreal, which brings obvious errors to the subsequent calculation of acceleration and accurate displacement. Addressing the above-mentioned problems, this paper proposes a ridge extracting correction algorithm based on modulus maxima frequency extraction; this method, based on a large number of experiments where rodless cylinders are used to simulate the motion of a gun automatic mechanism, conducts a detailed calculation and analysis of the experimental results. A comparison of the two algorithms' processing results, in terms of the speed, displacement and acceleration, suggests that the ridge extracting correction algorithm successfully corrects the frequency selection error, which draws a more continuous and, therefore, effective curve of the velocity change, and by so doing, the error of the displacement test (within 1.36 m displacement) is reduced from more than 3.6% to less than 0.58%, and the uncertainty dropped 97.07%. All these show that the accurate measurement of velocity, displacement and acceleration, with sudden and rapid velocity changes considered, is realized successfully.

Uterine artery Doppler velocimetry at mid-term gestation as a potential predictive factor for the resolution of placenta previa at the end of third trimester of pregnancy.

AIM: The incidence of placenta previa before the third trimester is high. But many cases resolve as pregnancy progresses. Our study was to evaluate the efficacy of uterine artery Doppler velocimetry at mid-term gestation for predicting placenta previa resolution in third trimester. METHODS: A single-center retrospective study was done. A study cohort of 504 subjects with placenta-cervix os distance measured both at 22-24 weeks and after 36 weeks of gestation and uterine artery Doppler velocimetry measured at 22-24 weeks of gestation were selected. The subjects were assigned to control group (n = 351), resolving group (n = 89) and placenta previa group (n = 64) according to their diagnosis of placenta previa at mid-term and the end of the third trimester. The averages of the bilateral ratio of uterine artery systolic to end-diastolic maximum blood flow velocity (S/D ratio), pulsatility index (PI) and resistance index (RI) were used for analysis. RESULTS: The means of S/D ratio, PI and RI of uterine arteries in the placenta previa group were significantly lower than that in either control group or resolving group. No differences were observed between control group and resolving group. The areas under the receiver operating characteristic curve were 0.7632, 0.7579 and 0.7644 for the means of S/D ratio, PI and RI, respectively (P < 0.0001). CONCLUSION: The means of S/D ratio, PI and RI of the uterine arteries at mid-term gestation are reduced in patients with persistent placenta previa, indicating unique pathogenic changes at mid-term gestation, and have the potential to be a predictive factor on placenta previa resolution.

Flow Control Based on Feature Extraction in Continuous Casting Process.

The flow structure in the mold of a continuous steel caster has a significant impact on the quality of the final product. Conventional sensors used in industry are limited to measuring single variables such as the mold level. These measurements give very indirect information about the flow structure. For this reason, designing control loops to optimize the flow is a huge challenge. A solution for this is to apply non-invasive sensors such as tomographic sensors that are able to visualize the flow structure in the opaque liquid metal and obtain information about the flow structure in the mold. In this paper, ultrasound Doppler velocimetry (UDV) is used to obtain key features of the flow. The preprocessing of the UDV data and feature extraction techniques are described in detail. The extracted flow features are used as the basis for real time feedback control. The model predictive control (MPC) technique is applied, and the results show that the controller is able to achieve optimum flow structures in the mold. The two main actuators that are used by the controller are the electromagnetic brake and the stopper rod. The experiments included in this study were obtained from a laboratory model of a continuous caster located at the Helmholtz-Zentrum Dresden Rossendorf (HZDR).

Visual Calibration for Multiview Laser Doppler Speed Sensing.

We present a novel calibration method for a multi-view laser Doppler speed sensing (MLDSS) system. In contrast with the traditional method where only the laser geometry is independently calibrated, the proposed method simultaneously optimizes all the laser parameters and directly associates the parameters with a motion sensing model. By jointly considering the consistency among laser Doppler velocimetry, the laser geometry and a visual marker tracking system, the proposed calibration method further boosts the accuracy of MLDSS. We analyzed the factors influencing the precision, and quantitatively evaluated the efficiency of the proposed method on several data sets.

Discrepancy in Doppler waveforms between two umbilical arteries in fetuses with absent or reversed end-diastolic flow: A prospective observational study.

PURPOSE: To asses the occurrence of discrepancies between the Doppler waveforms of the left and right umbilical arteries in their paravesical part in fetuses with absent or reversed end-diastolic flow in the free-floating umbilical cord. METHODS: This prospective observational study included pregnant women with fetal growth restriction or twin-to-twin transfusion syndrome. Umbilical arterial Doppler waveforms were obtained from both umbilical arteries in their intra-abdominal paravesical part. Doppler findings were recorded as present end-diastolic flow (PEDF)/absent end-diastolic flow (AEDF); AEDF/AEDF; AEDF/reversed end-diastolic flow (REDF); or REDF/REDF pattern. RESULTS: There were 49 fetuses with AEDF or REDF at the free-floating umbilical cord. Of these, 20 (40.8%) had a discrepancy in Doppler waveforms between the two umbilical arteries, with 14 (28.6%) showing PEDF/AEDF, 17 (34.7%) AEDF/AEDF, 6 (12.2%) AEDF/REDF, and 12 (24.5%) REDF/REDF pattern. CONCLUSION: Doppler waveforms showed discrepancies between the two umbilical arteries in 40.8% of pregnant women with AEDF or REDF in the free-floating umbilical cord. The presence of end-diastolic flow in one umbilical artery cannot exclude the possibility of AEDF in the other.

Aged garlic extract preserves cutaneous microcirculation in patients with increased risk for cardiovascular diseases: A double-blinded placebo-controlled study.

Laser Doppler velocimetry estimates tissue perfusion providing a record of microvascular blood flow. Patients with heart disease or diabetes mellitus have impaired microvascular perfusion leading to impaired wound healing. Aged garlic extract (AGE) has a positive effect on vascular elasticity. This study aimed to assess the effect of long-term treatment with AGE on cutaneous tissue perfusion. A total of 122 patients with Framingham Risk Score ≥ 10 were randomised in a double-blinded manner to placebo or 2400 mg AGE daily for 1 year and monitored. Cutaneous microcirculation was measured at 0 and 12 months using laser Doppler velocimetry. A repeated measures analysis of variance (ANOVA) with a Greenhouse-Geisser correction determined that mean post-occlusive reactive hyperaemia differed significantly between time points. The mean percent change between the two time points 0 and 12 months was 102, 64 (174, 15)% change for AGE and 78, 62 (107, 92)% change for the placebo group (F[1, 120] = 5. 95, P < 0.016), 12 months of AGE increases the microcirculation in patients with an increased risk for cardiovascular events estimated using the Framingham risk score. Increased microcirculation could hypothetically facilitate wound healing.

Selective IUGR in dichorionic twins: what can Doppler assessment and growth discordancy say about neonatal outcomes?

OBJECTIVE: The aim of the present study was to assess, in a population of dichorionic twin pregnancies with selective growth restriction, the effect of inter-twin differences by use of Doppler velocimetry and fetal growth discordancy on perinatal outcomes. METHODS: This was a retrospective study including dichorionic twin pregnancies from January 2008 to December 2015 at the Department of Obstetrics and Gynecology of Fondazione MBBM. Only dichorionic twin pregnancies affected by selective intrauterine growth restriction (IUGR) delivering at ≥24 weeks were included in the study. RESULTS: We found that twin pregnancies with inter-twin estimated fetal weight (EFW) discordance ≥15% were significantly associated with a higher risk of preterm delivery before 32 (P=0.004) and 34 weeks (P=0.04). Similarly, twin pregnancies with inter-twin abdominal circumference (AC) discordance ≥30° centiles were associated with a higher rate of neonatal intensive care unit (NICU) admission (P=0.02), neonatal resuscitation (P=0.02) and adverse neonatal composite outcome (P=0.04). Of interest, when comparing twin pregnancies according to Doppler study, growth restricted twins had a higher rate of composite neonatal outcome and in multivariate analysis, an abnormal Doppler was an independent risk factor for this outcome. CONCLUSIONS: Our study associated growth discrepancy with specific pregnancy outcomes, according to defined cut-offs. In addition, we demonstrated that an abnormal umbilical artery Doppler is independently associated with a composite neonatal adverse outcome in growth restricted fetuses.

Aortic Isthmus Flow Recording Predicts the Outcome of the Recipient Twin after Laser Coagulation in Twin-Twin Transfusion Syndrome.

INTRODUCTION: The objective was to assess the prognostic value of the systolic flow through the aortic isthmus in monochorionic pregnancies complicated by twin-twin transfusion syndrome (TTTS) treated by placental laser ablation. MATERIAL AND METHODS: Fetal echocardiography and outcome data of 105 cases of TTTS treated by laser photocoagulation of placental anastomoses were reviewed. Hemodynamic parameters were collected before and after treatment. The isthmic systolic index (ISI) was calculated as the peak systolic velocity/systolic nadir ratio. RESULTS: A total of 105 laser coagulations were studied. Fetal echocardiography pre- and post-laser were available in 68 cases, including 55 with data on aortic isthmic Doppler. Survival rates were 17, 22, and 61% for 0, 1, or 2 twins, respectively. At least 1 twin was delivered alive in 83% of the pregnancies. The mean gestational age at surgery was 21 weeks (range 16-26). Median ISI values were similar for donor and recipient twins, before and after laser ablation (all p > 0.05). A lower recipient ISI before laser was related to early recipient demise within 24 h (p = 0.04). DISCUSSION: A lower ISI before placental laser ablation for TTTS is associated with postoperative demise of the recipient twin.