A. H. Miyague

Three‐dimensional Doppler evaluation of single spherical samples from the placenta: intra‐ and interobserver reliability

To evaluate the intra‐ and interobserver reliability of assessment of three‐dimensional power Doppler (3D‐PD) indices from single spherical samples of the placenta.

Assessing repeatability of 3D Doppler indices obtained by static 3D and STIC power Doppler: a combinedin-vivo/in-vitroflow phantom study: Static 3D and STIC power Doppler indices

To compare the variability in vascularization flow index (VFI) seen in serial acquisitions obtained using spatiotemporal image correlation (STIC) and using conventional static three‐dimensional (3D) power Doppler (PD), for both in‐vitro and in‐vivo models, and to evaluate whether the curves formed by VFI values obtained from successive ‘frames’ in a STIC dataset are consistent and resemble the waveforms obtained by spectral Doppler analysis.

Fractional moving blood volume (FMBV) concept can be applied to 3D power Doppler quantification

We read with great interest a recent study in UOG that concluded that fractional moving blood volume (FMBV) cannot be applied to three-dimensional power Doppler (3DPD)1. In a region known to have 100% moving blood, the authors observed no differences in vascularization index (VI), flow index (FI) or vascularization flow index (VFI) when gain level was changed, which is the basis on which FMBV is applied to standardize vascularity measurements on two-dimensional imaging1. However, we believe that this study had an important weakness: the authors evaluated FMBV using only a low pulse repetition frequency (PRF): 0.9 KHz. Low PRFs increase the sensitivity to detect low blood velocity, but they also reduce the capacity of distinguishing between higher blood velocities, because any blood velocity over a certain limit will be quantified as 100%, regardless of the true velocity. The average value of blood flow velocity in the umbilical artery is probably higher than the limit established by a PRF of 0.9 KHz. Therefore, one might expect that all color values inside the brightest region of the umbilical artery would be 100%, regardless of gain, because the velocity would be far higher than the maximum threshold. Hence, we believe that the authors’ conclusions about the inapplicability of the FMBV technique to 3DPD could be premature. We performed a small study to investigate this hypothesis. Pregnant women aged > 18 years, with singleton pregnancy, placental insertion at the anterior uterine wall and no known diseases, who were undergoing a regular second-trimester ultrasound examination were invited to participate in this study. The research protocol was approved by the local ethics committee, and all women signed informed consent. 3DPD datasets were acquired at the insertion of the umbilical cord in the placenta, using fixed settings, except for PRF and gain: power, 100%; wall motion filter, low1; freq, mid; flow res, mid1; smooth, 5/6; ensemble, 12; line den, 7; power Doppler map, 5 (gently color, on); balance, G ≥ 200; artifact, on; L. filter, 2. We acquired four 3DPD datasets, at gains of −3, –6, –9 and −12, using PRFs of 0.9 KHz and 1.8 KHz, without moving the transducer between acquisitions. We assessed 3DPD indices (VI, FI and VFI) from small spherical samples inside the umbilical artery, close to its insertion into the placenta, evaluating a region of 100% moving blood. We evaluated and analyzed 10 pregnant women aged between 19 and 28 years. The VI from the smallest spherical samples of all acquired 3DPD datasets was −12 20 40 60 80

Biometry and fetal weight estimation by two‐dimensional and three‐dimensional ultrasonography: an intraobserver and interobserver reliability and agreement study

To evaluate and compare the intraobserver and interobserver reliability and agreement for the biparietal diameter (BPD), abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW) obtained by two‐dimensional ultrasound (2D‐US) and three‐dimensional ultrasound (3D‐US).

Influence of attenuation on three-dimensional power Doppler indices and STIC volumetric pulsatility index: a flow phantom experiment

Three-dimensional (3D) power Doppler indices (vascularization index (VI), flow index (FI) and vascularization flow index (VFI)) have been shown to correlate with flow and vascularity1; however, these indices are highly susceptible to machine settings and attenuation2. In this study, we sought to verify whether the volumetric pulsatility index (vPI) based on spatiotemporal image correlation (STIC) power Doppler3 is less dependent on attenuation than the original 3D power Doppler indices obtained from both static 3D and STIC datasets by evaluating a flow phantom. The study model is the same as that described in a previous publication4; essentially, it comprises a flow phantom in which a blood-mimicking fluid flows through a silicon tube, powered by an electric pulsatile pump (Figure 1). We inserted one of two different attenuation blocks, made from the same substances used in the flow phantom structure, each measuring 10 mm in thickness, between the ultrasound probe and the flow phantom5. These blocks had different concentrations of glass beads (1.8% and 4.4%) and therefore different coefficients of attenuation: 0.6 dB/MHz/cm (‘low attenuation’ experiment) and 1.0 dB/MHz/cm (‘high attenuation’ experiment). The preset ‘gynecologic’ was used and the following machine settings were maintained for all acquisitions: depth, 4.2 cm; power, 100%; gain, 0.0; WMF, mid1; PRF, 3.2 KHz;

Influence of Gain Adjustment on 3-Dimensional Power Doppler Indices and on Spatiotemporal Image Correlation Volumetric Pulsatility Indices Using a Flow Phantom

Spatiotemporal image correlation can be used to acquire 3‐dimensional power Doppler information across a single cardiac cycle. Assessment and comparison of the systolic and diastolic components of the data sets allow measurement of the recently introduced “volumetric pulsatility index” (vPI) through algorithms comparable with those used in 2‐dimensional Doppler waveform analysis. The vPI could potentially overcome the dependency on certain machine settings, such as power, color gain, pulse repetition frequency, and attenuation, since these factors would affect the power Doppler signal equally throughout the cardiac cycle. The objective of this study was to compare the effect of color gain on the vascularization index (VI), vascularization‐flow index (VFI), and vPI using an in vitro flow phantom model. We separated gains into 3 bands: −8 to −1 (no noise), −1 to +5 (low noise), and +5 to +8 (obvious noise). The vPI was determined from the 3‐dimensional VI or VFI using the formula vPI = (maximum − minimum)/mean. Using no‐noise gains, we observed that although the VI and VFI increased linearly with gain, the vPI was substantially less dependent on this adjustment. The VI and VFI continued to increase linearly with gain, whereas the vPI decreased slightly using low‐noise gains. When gain was increased above the lower limit of obvious noise (+5), the VI and VFI increased noticeably, and there were marked reductions in both vPI values. We conclude that the vPI is less affected by changes in color gain than the VI and VFI at no‐noise gains.

Maternal flow-mediated dilation and nitrite concentration during third trimester of pregnancy and postpartum period

Objectives. To compare maternal flow-mediated dilation (FMD) of the brachial artery and nitrite concentration between third trimester of pregnancy (3rdT) and postpartum (PP) period. Additionally, we will evaluate whether FMD correlates with nitrite concentration in both periods. Methods. Eligibility criteria was healthy women with singleton pregnancy, gestational age >28 weeks, nonsmokers, and no personal or family history of vascular disease. Each women was examined during 3rdT and between 8 and 12 weeks PP to evaluate FMD and nitrite concentration in whole blood. Women not examined in both periods were excluded. Values between both periods were compared using paired t tests. Correlation between FMD and nitrite was examined by Pearson correlation coefficient. Significance level set as p < 0.05. Results. We invited 42 pregnant women. Among them, 35 were eligible and 7 of them were excluded for not attending the PP evaluation resulting in 28 participants analyzed. We found no significant change in FMD (10.39 ± 5.57% vs. 8.42 ± 4.21%; p = 0.11; 3rdT vs. PP, respectively) and no significant change in nitrite concentration (257.41 ± 122.95 nmol/L vs. 237.16 ± 90.01 nmol/L; p = 0.28). Baseline brachial artery diameter had a significant reduction (3.11 ± 0.30 to 2.75 ± 0.34 mm; p < 0.01). No significant correlation between FMD and nitrite during 3rdT (r = −0.13; p = 0.50) or PP (r = 0.14; p = 0.48) was found. Conclusions. We did not observe significant changes in both FMD and nitrite concentration between third trimester and the PP period. FMD did not correlate with nitrite in both periods. More studies are needed to confirm our findings.

Importance of Pulse Repetition Frequency Adjustment for 3- and 4-Dimensional Power Doppler Quantification

To determine the influence of the pulse repetition frequency (PRF) and wall motion filter on the 3‐dimensional (3D) power Doppler vascularization‐flow index (VFI) and volumetric pulsatility index (PI) obtained from spatiotemporal image correlation (STIC) data sets acquired from a common carotid artery of a healthy participant.

Understanding the Influence of Flow Velocity, Wall Motion Filter, Pulse Repetition Frequency, and Aliasing on Power Doppler Image Quantification

Although power Doppler imaging has been used to quantify tissue and organ vascularity, many studies showed that limitations in defining adequate ultrasound machine settings and attenuation make such measurements complex to be achieved. However, most of these studies were conducted by using the output of proprietary software, such as Virtual Organ computer‐aided analysis (GE Healthcare, Kretz, Zipf, Austria); therefore, many conclusions may not be generalizable because of unknown settings and parameters used by the software. To overcome this limitation, our goal was to evaluate the impact of the flow velocity, pulse repetition frequency (PRF), and wall motion filter (WMF) on power Doppler image quantification using beam‐formed ultrasonic radiofrequency data.

Fetal thymus: visualization rate and volume by integrating 2D- and 3D-ultrasound during 2nd trimester echocardiography

Abstract Objective: To assess the visualization rate and transverse diameter of fetal thymus by two-dimensional ultrasound (2DUS) as well as the fetal thymus volume by three-dimensional ultrasound (3DUS) during the 2nd trimester echocardiography. Methods: A prospective cross-sectional study involving 100 normal fetuses between 18w0d and 23w6d was performed. The identification of fetal thymus and peri-thymic vessels was realized at level of three vessels and trachea (3VT). The transverse diameter was obtained placing a line cursor perpendicular to the line connecting the sternum and the spine. The fetal thymus volume was obtained by virtual organ computer-aided analysis (VOCAL) with 30° of rotation. We used the percentage of visualization rate of 2D structures and means and 95% confidence intervals (CI) for fetal thymus transverse diameter and volume. Results: The visualization rate of fetal thymus by 2DUS was of 100% in all gestational ages using the 3VT view. Addition of color Doppler ultrasound facilitates identification of the thy-box and enhanced the calculation of both fetal thymus transverse diameter and volume. The mean fetal thymus transverse diameter by 2DUS ranged from 11 mm at 18 weeks to 19 mm at 23 weeks of gestation. The mean fetal thymus volume by 3DUS ranged from 1.25 cm3 at 18 weeks to 2.61 cm3 at 23 weeks of gestation. Conclusion: We demonstrated a high visualization rate of fetal thymus and peri-thymic vessels by 2DUS during the 2nd trimester echocardiography. The measurements of transverse diameter by 2DUS and the volume by 3DUS also showed a high success rate.