Comparison of Variations Between Spectral Doppler and Gaussian Surface Integration Methods for Umbilical Vein Blood Volume Flow

Color Flow Ultrasound Spatial Sampling Beam Density for Partial Volume-Corrected Three-Dimensional Volume Flow (3DVF): Theory, Simulation, and Experiment

OBJECTIVE

The purpose of this study was to quantify the accuracy of partial volume-corrected three-dimensional volume flow (3DVF) measurements as a function of spatial sampling beam density using carefully-designed parametric analyses in order to inform the target applications of 3DVF.

METHODS

Experimental investigations employed a mechanically-swept curvilinear ultrasound array to acquire 3D color flow (6.3 MHz) images in flow phantoms consisting of four lumen diameters (6.35, 4.88, 3.18 and 1.65 mm) with volume flow rates of 440, 260, 110 and 30 mL/min, respectively. Partial volume-corrected three-dimensional volume flow (3DVF) measurements, based on the Gaussian surface integration principle, were computed at five regions of interest positioned between depths of 2 and 6 cm in 1 cm increments. At each depth, the color flow beam point spread function (PSF) was also determined, using in-phase/quadrature data, such that 3DVF bias could then be related to spatial sampling beam density. Corresponding simulations were performed for a laminar parabolic flow profile that was sampled using the experimentally-measured PSFs. Volume flow was computed for all combinations of lumen diameters and the PSFs at each depth.

RESULTS

Accurate 3DVF measurements, i.e., bias less than ±20%, were achieved for spatial sampling beam densities where at least 6 elevational color flow beams could be positioned across the lumen. In these cases, greater than 8 lateral color flow beams were present. PSF measurements showed an average lateral-to-elevational beam width asymmetry of 1:2. Volume flow measurement bias increased as the color flow beam spatial sampling density within the lumen decreased.

CONCLUSION

Applications of 3DVF, particularly those in the clinical domain, should focus on areas where a spatial sampling density of 6 × 6 (lateral x elevational) beams can be realized in order to minimize measurement bias. Matrix-based ultrasound arrays that possess symmetric PSFs may be advantageous to achieve adequate beam densities in smaller vessels.

Umbilical Vein Flows and Cardiac Size, Shape, and Ventricular Contractility in Fetuses With Estimated Weight Less-Than 10th Centile

OBJECTIVES

In a cohort of patients with estimated fetal weights (EFWs) <10th centile, we aimed 1) to compare the prevalence of abnormalities of fetal 4-chamber view (4CV) cardiac size, shape, and ventricular contractility in fetal growth restricted (FGR) and small-for-gestational-age (SGA) fetuses and 2) to compare umbilical vein flow (UVF) measurements to standard Doppler surveillance in predicting abnormalities of cardiac function.

METHODS

Prospective observational cohort study of fetuses with EFW <10th percentile. Measurements of size and shape used were 4CV transverse width, 4CV cardiac area, 4CV global sphericity index, and right-to-left ventricular mid-chamber width ratio. Variables of contractility used were fractional shortening change at the mid-ventricle chamber, global longitudinal strain, fractional area change, and left ventricular cardiac output. The UVF and standard Doppler surveillance including umbilical artery (UA), middle cerebral artery, and cerebroplacental ratio (CPR) were collected. Control data were from previously published studies.

RESULTS

A total of 95 fetuses with EFWs <10th centile were included in the study. The rates of abnormalities of cardiac size and shape and ventricular contractility were all significantly elevated compared with normally grown control fetuses but similar between FGR and SGA fetuses. In a subset of 76 patients with UVF data, evaluation UVF identified more patients with any abnormality of contractility compared with UA (37.9 vs 17.2%, P = .02).

CONCLUSIONS

The addition of UVF doubled the detection rate of ventricular contractility abnormalities. The addition of UVF should be considered in the surveillance of FGR and SGA fetuses to further stratify the severity of hypoxemia and to identify those at greater risk for future cardiovascular dysfunction.

Measurement of Cerebral Metabolism Under Non-Chronic Hemodynamic Conditions

BACKGROUND

Blood flow to the brain is a critical physiological function and is useful to monitor in critical care settings. Despite that, a surrogate is most likely measured instead of actual blood flow. Such surrogates include velocity measurements in the carotid artery and systemic blood pressure, even though true blood flow can actually be obtained using MRI and other modalities. Ultrasound is regularly used to measure blood flow and is, under certain conditions, able to provide quantitative volumetric blood flow in milliliters per minute. Unfortunately, most times the resulting flow data is not valid due to unmet assumptions (such as flow profile and angle correction). Color flow, acquired in three dimensions, has been shown to yield quantitative blood flow without any assumptions (3DVF).

METHODS

Here we are testing whether color flow can perform during physiological conditions common to severe injury. Specifically, we are simulating severe traumatic brain injury (epidural hematoma) as well as hemorrhagic shock with 50% blood loss. Blood flow was measured in the carotid artery of a cohort of 7 Yorkshire mix pigs (40-60 kg) using 3DVF (4D16L, LOGIQ 9, GE HealthCare, Milwaukee, WI, USA) and compared to an invasive flow meter (TS420, Transonic Systems Inc., Ithaca, NY, USA).

RESULTS

Six distinct physiological conditions were achieved: baseline, hematoma, baseline 2, hemorrhagic shock, hemorrhagic shock plus hematoma, and post-hemorrhage resuscitation. Mean cerebral oxygen extraction ratio varied from 40.6% ± 13.0% of baseline to a peak of 68.4% ± 15.6% during hemorrhagic shock. On average 3DVF estimated blood flow with a bias of -9.6% (-14.3% root mean squared error) relative to the invasive flow meter. No significant flow estimation error was detected during phases of flow reversal, that was seen in the carotid artery during traumatic conditions. The invasive flow meter showed a median error of -11.5% to 39.7%.

CONCLUSIONS

Results suggest that absolute volumetric carotid blood flow to the brain can be obtained and potentially become a more specific biomarker related to cerebral hemodynamics than current surrogate markers.

Comment on Barbieri et al. Umbilical Vein Blood Flow in Uncomplicated Pregnancies: Systematic Review of Available Reference Charts and Comparison with a New Cohort. J. Clin. Med. 2023, 12, 3132

We would like to comment on the systemic review article published in the Journal of Clinical Medicine by Barbieri et al [...].

Placental assessment using spectral analysis of the envelope of umbilical venous waveforms in sheep

INTRODUCTION

This study was designed to test the efficacy of an ultrasound flow measurement method to evaluate placental function in a hyperandrogenic sheep model that produces placental morphologic changes and an intrauterine growth restriction (IUGR) phenotype.

MATERIALS AND METHODS

Pregnant ewes were assigned randomly between control (n = 12) and testosterone-treatment (T-treated, n = 22) groups. The T-treated group was injected twice weekly intramuscularly (IM) with 100 mg testosterone propionate. Control sheep were injected with corn oil vehicle. Lambs were delivered at 119.5 ± 0.48 days gestation. At the time of delivery of each lamb, flow spectra were generated from one fetal artery and two fetal veins, and the spectral envelopes examined using fast Fourier transform analysis. Base 10 logarithms of the ratio of the amplitudes of the maternal and fetal spectral peaks (LRSP) in the venous power spectrum were compared in the T-treated and control populations. In addition, we calculated the resistive index (RI) for the artery defined as ((peak systole - min diastole)/peak systole). Two-tailed T-tests were used for comparisons.

RESULTS

LRSPs, after removal of significant outliers, were -0.158 ± 0.238 for T-treated and 0.057 ± 0.213 for control (p = 0.015) animals. RIs for the T-treated sheep fetuses were 0.506 ± 0.137 and 0.497 ± 0.086 for controls (p = 0.792) DISCUSSION: LRSP analysis distinguishes between T-treated and control sheep, whereas RIs do not. LRSP has the potential to identify compromised pregnancies.

Bedside Cerebral Blood Flow Quantification in Neonates

Measurement of blood flow to the brain in neonates would be a very valuable addition to the medical diagnostic armamentarium. Such conditions such as assessment of closure of a patent ductus arteriosus (PDA) would greatly benefit from such an evaluation. However, measurement of cerebral blood flow in a clinical setting has proven very difficult and, as such, is rarely employed. Present techniques are often cumbersome, difficult to perform and potentially dangerous for very low birth weight (VLBW) infants. We have been developing an ultrasound blood volume flow technique that could be routinely used to assess blood flow to the brain in neonates. By scanning through the anterior fontanelles of 10 normal, full-term newborn infants, we were able to estimate total brain blood flows that closely match those published in the literature using much more invasive and technically demanding methods. Our method is safe, easy to do, does not require contrast agents and can be performed in the baby's incubator. The method has the potential for monitoring and assessing blood flows to the brain and could be used to routinely assess cerebral blood flow in many different clinical conditions.

Umbilical Vein Pulse Wave Spectral Analysis: A Possible Method for Placental Assessment Through Evaluation of Maternal and Fetal Flow Components

OBJECTIVES

Placental blood flow analysis is complicated by having both maternal and fetal flow components. Using the Fast Fourier Transform (FFT) of the umbilical venous pulse wave spectra (PW) envelope, we could simultaneously assess maternal/fetal blood flow in the placenta and investigate if normal and intrauterine growth restriction (IUGR)/pre-eclamptic pregnancies could be distinguished.

METHODS

This retrospective study included normal gestations (N = 11) and gestations with IUGR, pre-eclampsia, or both (N = 13). Umbilical vein PW were acquired and spectral envelopes were identified as a function of time and analyzed by FFT. Base-10 logarithms of the ratios of the maternal/fetal spectral peaks (LRSP) were compared in normal and IUGR/pre-eclamptic populations (two-tailed t-test). Body mass index (BMI), gestational age at scan time, placental position, and weight-normalized umbilical vein blood volume flow (two-tailed t-test, analysis of variance [ANOVA] analysis) were tested. P < .05 was considered significant.

RESULTS

The LRSP for normal and IUGR/pre-eclamptic pregnancies were 0.141 ± 0.180 and -0.072 ± 0.262 (mean ± standard deviation), respectively (P = .033). We detected differences between normal gestations and combinations of LRSP and weight-normalized umbilical venous blood flows. Placental effects based on LRSPs and blood flow may act synergistically in cases with both pre-eclampsia and IUGR (P = .014). No other significant associations were seen.

CONCLUSIONS

In this preliminary study, we showed that umbilical venous flow contains markers related to placental maternal/fetal blood flow, which can be used to assess IUGR and pre-eclampsia. When coupled with umbilical cord blood flow, this new marker may potentially identify the primary causes of the two conditions.

Fetal and Neonatal Middle Cerebral Artery Hemodynamic Changes and Significance under Ultrasound Detection in Hypertensive Disorder Complicating Pregnancy Patients with Different Severities

Colour Doppler ultrasound was applied for monitoring the hemodynamic parameters of fetal uterine artery (UtA), umbilical artery (UA), and middle cerebral artery (MCA) during pregnancy. In hypertension disease complicating pregnancy, these hemodynamic measures and their therapeutic applicability value were reviewed (HDCP). 120 singleton pregnant women were chosen, with 40 cases of mild preeclampsia (mild group), 40 cases of severe preeclampsia (severe group), and 40 normal control pregnant women (control group). The hemodynamic parameters of UtA, MCA, and UA were monitored in the three groups, including pulsatility index (PI), resistance index (RI), and the systolic/diastolic velocity (S/D). The parameters PI, RI, S/D, and venous catheter shunt rate (Qdv/Quv) of UtA and UA in the severe group were higher than those in the normal group and the mild group, showing the differences statistically significant ( $P<0.05$ ). The PI, RI, and S/D of MCA in the severe group were lower than those in the normal group and the mild group ( $P<0.05$ ). The changing trends of PI, RI, and S/D in the severe group were all first increased and then decreased in the early, middle, and later pregnancy ( $P<0.05$ ). The area under the curve (AUC) was 0.98 in the receiver operating characteristic (ROC) curve created using a combination of hemodynamic measures and pregnancy outcomes, and the sensitivity and specificity for predicting bad outcomes were 94.7 percent and 96.4 percent, respectively. Colour Doppler ultrasound may accurately detect changes in the PI, RI, and S/D of UtA, MCA, and UA in pregnant women and serve as a reference for determining the intrauterine state of the fetuses and predicting bad pregnancy outcomes. In particular, the parameters in later pregnancy were higher worthy of diagnostic value for adverse pregnancy outcomes. The combination of various parameters could make an improvement of the diagnostic accuracy and provide a basis for guiding treatment as well as determining the optimal timing of delivery.

Ultrasonographic Tissue Perfusion in Peri-implant Health and Disease

Color flow ultrasonography has played a crucial role in medicine for its ability to assess dynamic tissue perfusion and blood flow variations as an indicator of a pathologic condition. While this feature of ultrasound is routinely employed in various medical fields, its intraoral application for the assessment of tissue perfusion at diseased versus healthy dental implants has never been explored. We tested the hypothesis that quantified tissue perfusion of power Doppler ultrasonography correlates with the clinically assessed inflammation of dental implants. Specifically, we designed a discordant-matched case-control study in which patients with nonadjacent dental implants with different clinical diagnoses (healthy, peri-implant mucositis, or peri-implantitis) were scanned and analyzed with real-time ultrasonography. Forty-two posterior implants in 21 patients were included. Ultrasound scans were obtained at the implant regions of midbuccal, mesial/distal (averaged as interproximal), and transverse to compute the velocity- and power-weighted color pixel density from color velocity (CV) and color power (CP), respectively. Linear mixed effect models were then used to assess the relationship between the clinical diagnoses and ultrasound CV and CP. Overall, the results strongly suggested that ultrasound's quantified CV and CP directly correlate with the clinical diagnosis of dental implants at health, peri-implant mucositis, and peri-implantitis. This study showed for the first time that ultrasound color flow can be applicable in the diagnosis of peri-implant disease and can act as a valuable tool for evaluating the degree of clinical inflammation at implant sites.