Evaluation of the effect of machine settings on quantitative three-dimensional power Doppler angiography: an in-vitro flow phantom experiment

How to use power Doppler ultrasound in transvaginal assessment of uterine fibroids

Measuring vascularization in uterine fibroids is important for their diagnosis, treatment and prognosis. Vascularization can be measured by power Doppler ultrasound. The power Doppler signal depends on fibroid characteristics and on a variety of ultrasound-machine settings. Literature describing which machine settings influence the power Doppler signal is limited. Each manufacturer names settings and presets at their own discretion, with little information available publicly. Consistency of machine settings is important for correct interpretation of images in daily practice and is essential in yielding reproducible data for research. The aims of this paper, drawing from both a literature search and semistructured interviews with ultrasound-machine engineers and clinical experts in gynecological ultrasound, were: (1) to provide comprehensive background information on ultrasound physics and fibroid characteristics; (2) to present an overview of machine settings relevant to both two- and three-dimensional power Doppler, including power Doppler frequency, pulse repetition frequency, gain, wall-motion filter, acoustic power, persistence and signal rise; and (3) to provide a step-by-step tutorial on the optimal settings for vascular evaluation of uterine fibroids using power Doppler. The step-by-step tutorial comprises six steps to optimize the power Doppler signal, create a preset and acquire a reliable three-dimensional volume. This step-by-step tutorial should help research groups and clinicians to use power Doppler correctly and reproducibly in the evaluation of uterine fibroids. © 2022 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fibroid vascularisation assessed with 3D Power Doppler as predictor for fibroid related symptoms and quality of life; a pilot study

Background

Uterine fibroids present differently, from well vascularised up to calcified, with some causing heavy menstrual bleeding (HMB).

Objectives

To investigate the association between fibroid vascularisation and HMB, other fibroid related symptoms and quality of life (QOL).

Materials and Methods

A single centre pilot study was carried out in the Netherlands. Women with a maximum of two fibroids who chose expectant management were included. 3D sonography including power doppler was performed at baseline and at 3, 6 and 12 months follow up. Women were asked to complete the Pictorial Blood Assessment Chart (PBAC) and Uterine Fibroid Symptom and Quality of Life (UFS-QOL) questionnaires at every visit.

Main outcome measure

The association between fibroid vascularisation and HMB.

Results

53 women were included in the study. Baseline fibroid vascularisation, measured as vascular index (VI) is associated with PBAC score; a 1% higher VI at baseline leads to an 11 point increase in PBAC score over time (RC 10.99, p=0.05, 95% CI -0.15 – 22.12). After correction for the baseline variables ethnicity and fibroid type the association becomes stronger (P<0.05). Fibroid volume at baseline and HMB are also associated: a 1 cm3 larger fibroid leads to 0.6 points increase in PBAC score over time (RC 0.56, p=0.03, 95% CI 0.05 – 1.07).

Conclusions

This study highlights that both fibroid vascularisation and fibroid volume may be associated with an increase in menstrual blood loss, other fibroid related symptoms and QOL over time.

What is new?

We used 3D power doppler to predict symptomatic fibroids.

New insights into human functional ultrasound imaging

Ultrasound imaging is a vital tool for exploring in vivo the placental function which is essential to understand pathological phenomena such as preeclampsia or intrauterine growth restriction. As technology advances including ready availability of three-dimensional (3D) probes and novel software, new markers of placental function become possible. The objective of this review was to provide an overview of the new ultrasound markers of placental function with a focus on the potential clinical application of three-dimensional power Doppler (3DPD). A broad-free text literature search was undertaken based on human placental studies and sixty full-text studies were included in this review. Three-dimensional power Doppler is a promising technique to predict preeclampsia in the first trimester. However, the influence of external factors such as body mass index, parameter standardisation and machine settings still need to be addressed. Contrast-enhanced ultrasound is currently reserved for research, because the required injected contrast mediums are not currently approved for use in pregnancy, although the safety data is reassuring.

A 10-Year Retrospective Review of Prenatal Applications, Current Challenges and Future Prospects of Three-Dimensional Sonoangiography

Realistic reconstruction of angioarchitecture within the morphological landmark with three-dimensional sonoangiography (three-dimensional power Doppler; 3D PD) may augment standard prenatal ultrasound and Doppler assessments. This study aimed to (a) present a technical overview, (b) determine additional advantages, (c) identify current challenges, and (d) predict trajectories of 3D PD for prenatal assessments. PubMed and Scopus databases for the last decade were searched. Although 307 publications addressed our objectives, their heterogeneity was too broad for statistical analyses. Important findings are therefore presented in descriptive format and supplemented with the authors’ 3D PD images. Acquisition, analysis, and display techniques need to be personalized to improve the quality of flow-volume data. While 3D PD indices of the first-trimester placenta may improve the prediction of preeclampsia, research is needed to standardize the measurement protocol. In highly experienced hands, the unique 3D PD findings improve the diagnostic accuracy of placenta accreta spectrum. A lack of quality assurance is the central challenge to incorporating 3D PD in prenatal care. Machine learning may broaden clinical translations of prenatal 3D PD. Due to its operator dependency, 3D PD has low reproducibility. Until standardization and quality assurance protocols are established, its use as a stand-alone clinical or research tool cannot be recommended.

First trimester screening for pre-eclampsia and intrauterine growth restriction using three-dimensional Doppler angiography (SPIRIT): protocol for a multicentre prospective study in nulliparous pregnant women

INTRODUCTION

Pre-eclampsia (PE) and intrauterine growth restriction (IUGR) are two major pregnancy complications, related to chronic uteroplacental hypoperfusion. Nowadays, there is no screening or diagnostic test for uteroplacental vascularisation deficiency in pregnant women. Since 2004, 3 three-imensional power Doppler (3DPD) angiography has been used for the evaluation of uteroplacental vascularisation and three vascular indices are usually calculated: Vascularisation Index (VI), Flow Index (FI) and vascularisation-FI (VFI). A high intraobserver and interobserver reproducibility and a potential interest for placental function study were reported by our team and others.The main objective of our study is to determine differences in 3DPD indices at first trimester between pregnancies defined at their outcome as uncomplicated pregnancy, PE (mild and severe) and IUGR in nulliparous women.

METHODS AND ANALYSIS

This is a national multicentre prospective cohort study conducted in four French maternity units. We expect to include 2200 women in a period of 36 months. The nulliparous pregnant women will be recruited during their first trimester consultation (11-13+6 gestation week (GW)).The 3DPD and uterine artery Doppler acquisition will be included in the current routine 11-13+6 GW ultrasound. Also, additional blood samples will be taken for biomarker analysis (PAPP-A and P1GF) and biological collection. Uteroplacental VIs (FI and VFI) will be measured. For each subgroup (uncomplicated pregnancy, PE and IUGR), mean values in 3DPD indices will be computed and compared using a pairwise t test with a Bonferroni correction p value adjustment.

ETHICS AND DISSEMINATION

The study was approved by the French Ethics Committee, the Comité de Protection des Personnes SUD MEDITERRANEE IV on 13 February 2018 with reference number 17 12 03. The results of this study will be published in a peer-reviewed journal and will be presented at relevant conferences.

TRIAL REGISTRATION NUMBER

NCT03342014; Pre-results. PHRCN-16-0567.

Cerebral hemodynamic response to short-term maternal hyperoxygenation in fetuses with borderline small left hearts

BACKGROUND

Hypoxia delays brain maturation and contributes to neurodevelopmental morbidity in fetuses with congenital heart defects (CHDs). Maternal hyperoxygenation (MH) can, in theory, promote oxygen/nutrient delivery to the fetal brain, owing to an improved heart structure/function and increased fetal oxygen content. We aimed to determine whether MH alters fetal cerebral hemodynamics in fetuses with CHD.

METHODS

Twenty-eight fetuses with borderline small left hearts and 28 age-matched normal fetuses were enrolled and subdivided by gestational age (GA): 23^+ 0 ~ 27^+ 6 weeks and 28^+ 0 ~ 36^+ 6 weeks. The middle cerebral artery pulsatility index (MCA-PI), vascular index (VI), flow index (FI) and vascular/flow index (VFI) were measured with baseline room air, after 10 min of MH and after 10 min of recovery for all subjects.

RESULTS

MCA-PI, VI, FI and VFI did not differ with MH in the normal fetuses. In fetuses with borderline small left hearts, MCA-PI increased and VI, FI and VFI significantly decreased during the 3rd trimester (from 1.44 ± 0.27, 3.19 ± 0.87, 56.91 ± 9.19, and 1.30 ± 0.33 at baseline to 1.62 ± 0.15, 2.37 ± 0.37, 45.73 ± 4.59, and 0.94 ± 0.15 during MH, respectively, P < 0.05), but this response was not apparent during mid-gestation (p > 0.05). These parameters returned to the baseline levels during the recovery phase. The change in cerebral perfusion depended on the baseline MCA-PI and increased the combined cardiac index (CCOi).

CONCLUSIONS

MH alters the cerebral hemodynamics of fetuses with borderline small left hearts during the third trimester. Further investigation is needed to determine whether MH may benefit brain growth and neurodevelopment in this high-risk population.

Intra-placental arterial Doppler: A marker of fetoplacental vascularity in late-onset placental disease?

INTRODUCTION

Late-gestation adverse pregnancy outcome is associated with reduced placental villous vascularity but rarely with a frankly abnormal umbilical artery Doppler waveform. The clinical utility of umbilical artery Doppler velocimetry in late gestation is limited by poor understanding of what aspect(s) of placental structure and function the impedance reflects. We hypothesized that placental arterial circulation impedance reflects placental vascularity and arterial function.

MATERIAL AND METHODS

This was a secondary analysis of data from the FEMINA2 study, a study of pregnancy outcome after reduced fetal movement. Forty-three pregnancies that delivered within 7 days of ultrasound assessment were examined. Impedance was quantified by pulsatility index (PI) from umbilical, chorionic plate arteries, and intra-placental arteries. Site-specific PI was compared with villous vascularity (CD31 immunostaining) and placental arterial function (wire myography) by regression analysis (P < .01) where factor analysis suggested potential co-variance (Eigen value > 2).

RESULTS

Pulsatility index decreased with proximity to the placental microvasculature (P < .0001). Intra-placental artery PI correlated significantly with vessel number (R²  = 0.40, P = .0007). No significant relations between umbilical or chorionic plate artery PI and villous vascularity were found (P ≥ .11 and P ≥ .042). No significant co-variance was suggested between PI at any Doppler sampling site and ex vivo placental arterial function indices. Measurement reliability (intraclass correlation coefficient) was highest in the umbilical artery (PI 0.75 and 0.50 for intra- and interoperator reliability, respectively) and lowest in the intra-placental arteries (PI 0.55 and 0.41, respectively). Systematic bias in umbilical artery PI was observed between observers, but not at other Doppler sampling sites.

CONCLUSIONS

More vascular placentas ex vivo are associated with reduced intra-placental artery Doppler impedance in utero. Although umbilical (but not intra-placental) artery Doppler PI is associated with adverse outcome after reduced fetal movement, this predictive ability does not appear to be through assessment of placental vascularity or chorionic plate arterial function. The inferior reliability of intra-placental artery Doppler, although similar to previously published reliability of umbilical artery Doppler, impairs its ability to detect subtle differences in placental vascularity, and must be significantly improved before it could be considered a clinically useful test.

Differences in fibroid vascularity after three months of pre-treatment with leuprolide acetate or ulipristal acetate: A pilot study

OBJECTIVES

To investigate differences in volume and fibroid vascularity expressed in vascular index after three months of (pre-)treatment with leuprolide acetate (LPA) or ulipristal acetate (UPA).

STUDY DESIGN

Prospective pilot study of 23 premenopausal women with uterine fibroids. Patients who started with LPA or UPA and had at least one fibroid with a size between 3 and 12 cm, were included consecutively. Per patient one fibroid was evaluated. The ultrasound was performed at baseline and after three months using LPA or UPA using a standardized protocol. 3D scans were evaluated using VOCAL software to calculate outcomes of volume, vascular index (VI) without shell ("shell off") and of the inner shell.

RESULTS

Four patients in the LPA group were additionally excluded from analyses due to insufficient quality of 3D scans. In the ten remaining patients (pre-)treated with LPA both volume and vascular indices of the fibroid reduced significantly after three months from a median of 224.3 cm³ (IQR 338.0) to 124.8 cm³ (IQR 186.1) (p = 0,05); median VI fibroid (shell off) reduced from 4.30 (IQR 4.72) to 0.93 (IQR 1.54) (p = 0,05); and VI inner capsule from 6.34 (IQR 7.51) to 1.28 (IQR 2.13) (p = 0,05). After UPA (n = 9) changes in fibroid volume and vascular indices did not reach statistical significance. Volume reduced from 248.5 cm³ (IQR 271.9) to 140.7 cm³ (IQR 209.4) (p > 0,05); median VI fibroid (shell off) from 2.97 (IQR 3.81) to 2.90 (IQR 4.82) (p > 0,05); and VI inner capsule from 2.56 (IQR 7.48) to 2.89 (IQR 4.83) (p > 0,05). A strong positive correlation was found between the VI of the fibroid (shell off) at baseline with the volume change after three months of LPA use (LPA r = 0.636, p = 0.048, 95% CI = -0.03 - 1.00).

CONCLUSION

In this pilot study we observed a consistent and statistically significant decrease in VI and fibroid volume after three months of LPA treatment in patients with uterine fibroids. The decrease in fibroid volume and VI was less consistent after UPA use. The strong correlation between the VI at baseline and volume reduction, may in theory be used to predict the volume reduction after LPA.

Three-dimensional power Doppler ultrasound evaluation of placental blood flow in normal monochorionic diamniotic twin pregnancies

Background

Monochorionic diamniotic (MCDA) twin pregnancies are at higher risk of adverse outcomes and complications, which are attributed to the influence of placental morphology in MCDA twins. Monitoring of placental function is an important index for clinical decisions. The aim of our study was to evaluate the placental blood flow estimated using three-dimensional power Doppler (3D-PD) ultrasound and the vascular indices distribution with gestational age (GA) in normal MCDA twin pregnancies.

Methods

One hundred four MCDA twin pregnancies and 106 singleton pregnancies (GA range, 14–32 weeks) were included in this prospective study. 3D-PD volume data of each fetus was obtained separately from the placenta at the site of umbilical cord insertion. We analyzed the volume data using sonobiopsy technique. The placental vascularization index (VI), flow index (FI) and vascularizationflow index (VFI), were auto-calculated. The means and standard deviation values of three vascular indices per fetus were calculated and regression analysis of the vascular indices as a function of GA was performed in twin pregnancies. The vascular indices of twin and singleton pregnancies were compared using independent t-test.

Results

There were no significant differences in VI, FI or VFI among the fetuses of twins (p > 0.05). These vascular indices increased over the course of pregnancy (p < 0.05). We obtained the regression equations for the indices as a function of GA in days: VI = exp. (4.369–28.533/GA) (R² = 0.699, p < 0.05), FI = exp. (3.916–13.003/GA) (R² = 0.511, p < 0.05), and VFI = exp. (3.577–37.468/GA) (R² = 0.675, p < 0.05). There were no significant differences in three vascular indices between MCDA twin and singleton groups (p > 0.05).

Conclusions

3D-PD placental data using sonobiopsy technique could reflect the placental blood flow of each twin, which could be applied to the study of placental perfusion in MCDA twin pregnancies. This study also presented the vascular indices distribution with GA in normal twin pregnancies, which might be useful for early detection of MCDA complications.

Placental vascularization indices and prediction of pre-eclampsia in high-risk women

OBJECTIVE

To assess ability of first and second trimester Placental Vascularization Indices (PVIs) to predict pre-eclampsia (PE) in high-risk pregnancies.

METHOD

PVIs derived from 3-Dimensional power Doppler imaging were measured at 11+0-13 + 6 (n = 194) and 19+0-21 + 6 weeks (n = 195). Logistic regression (LR) models used PE as the outcome. To quantify added value of PVIs to baseline characteristics in predicting PE, integrated discrimination improvement (IDI) and net reclassification improvement (NRI) indices were calculated.

RESULTS

Overall rate of PE was 12% (n = 26). Lower first trimester PVIs were seen in women with PE (mean, SD); Vascularization Index (VI,%): 10.0 (6.2) v 14.7 (7.6), P = 0.005, Flow Index (FI): 37.7 (9.1) v 42.9 (10.4), P = 0.03, Vascularization Flow Index (VFI): 3.8 (2.5) v 6.6 (4.0), P < 0.001). All first trimester PVIs predicted PE in LR models adjusted for covariates. IDI and NRI analyses confirmed added clinical utility of VI (IDI 0.05, P = 0.004; NRI 0.66, P < 0.001) and VFI (IDI 0.06, P = 0.004; NRI 0.53, P = 0.91). In the second trimester, FI was lower in women with PE (39.6 (9.1) v 44.4 (8.6), P = 0.01) and predicted PE in adjusted LR models (standardised OR 0.53, 95% CI 0.29-0.97, P = 0.04). FI discriminated between cases and non-cases of PE (IDI 0.04, P = 0.04).

CONCLUSION

First trimester placental vascularization indices (VI, FI and VFI) have the potential to predict PE in high-risk pregnancies, with FI remaining predictive in the second trimester.

Three-dimensional indices of renal perfusion in normal pregnancy and pre-eclampsia

INTRODUCTION

We compared renal perfusion in normal pregnant women and women with pre-eclampsia using three-dimensional (3D) ultrasound. We measured the flow index (FI), vascular index (VI) and vascularisation flow index (VFI) which are believed to reflect vascularity and flow intensity.

METHODS

Fourteen patients with normal pregnancy and 16 patients with pre-eclampsia were recruited. Imaging was conducted using a Voluson E8 machine and a 6-MHz trans-abdominal probe. The inferior border of the maternal left kidney was scanned. Volumes were acquired using 3D power Doppler angiography (3D-PDA). The FI, VI and VFI were generated using 'histogram' facility.

RESULTS

Maternal characteristics between normal pregnant women and women with pre-eclampsia were not different in terms of maternal age, gestation or body mass index. Depth of insonnation was not different between groups. The FI, VI and the VFI were not different between groups. The mean (SD) for FI was 27.9 (7.4) vs. 27.1 (6.5) between women with normal pregnancy vs. women with pre-eclampsia. For VI, mean (SD) was 72.3(31.6) vs. 79.4 (28.7) respectively. For VFI, mean (SD) was 20.8 (10.8) vs. 20.8 (8.1) respectively. Using the Mann-Whitney U test, no statistical differences between groups were apparent. There was no correlation between FI measurements and maternal creatinine (Pearson's R square = 0.04; p = 0.45) or with maternal urea levels (Pearson's R square = 0.20; p = 0.10).

CONCLUSION

Using 3D ultrasound, we failed to demonstrate a difference in maternal renal perfusion in normal pregnancy compared to pre-eclampsia. The lack of observed difference may be a reflection of the high variability in 3D measurements (i.e. poor investigative tool) rather than a true lack of difference in renal perfusion.

Receiver-Operating Characteristic Analysis of Eigen-Based Clutter Filters for Ultrasound Color Flow Imaging

The eigen-based filter has theoretically established itself as a potent solution in ultrasound color flow imaging (CFI) for combating against clutter arising from moving tissues. Yet, it remains poorly understood on how much gain in flow detection sensitivity and specificity can be delivered by this adaptive clutter filter. Here, we investigated the receiver operating characteristic (ROC) of the eigen-based clutter filter to statistically evaluate its efficacy. Our investigation was conducted using a new vascular phantom testbed that incorporated both intrinsic tissue motion (vessel pulsation: 7.58 cm/s peak velocity) and extrinsic tissue motion (vibration: 5-Hz frequency, 2.98 cm/s peak velocity), as well as pulsatile flow (pulse rate: 60 beats/min; systolic flow rate: 6.5 mL/s). The eigen-filter (single-ensemble formulation) was applied to CFI raw data sets obtained from the phantom's short-axis view (slow-time ensemble size: 12; pulse repetition frequency: 2 kHz; and ultrasound frequency: 5 MHz), and post-filter Doppler power was compared between flow and tissue regions. Results show that, in the presence of vessel pulsation and tissue vibration, the eigen-filter yielded a high true positive rate in depicting flow pixels in CFI frames (0.945 and 0.917, respectively, during peak systole and end diastole at 60° beam-flow angle), while maintaining a low false alarm rate (0.10) in rendering tissue pixels. Also, the eigen-filter posed ROC curves whose area under curve was higher than those for the polynomial regression filter (statistically significant; t-test p values were less than 0.05). These findings serve well to substantiate the merit of using eigen-filters to enhance the vascular visualization capability of CFI.

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

OBJECTIVES

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.

METHODS

The setup consisted of a blood-mimicking fluid flowing through a phantom. Radiofrequency signals were collected using PRFs ranging from 0.6 to 10 kHz for 6 different flow velocities (5-40 cm/s). Wall motion filter cutoff frequencies were varied between 50 and 250 Hz.

RESULTS

The power Doppler magnitude was deeply influenced by the WMF cutoff frequency. The effect of using different WMF values varied with the PRF; therefore, the power Doppler signal intensity was dependent on the PRF. Finally, we verified that power Doppler quantification can be affected by the aliasing effect, especially when using a PRF lower than 1.3 kHz.

CONCLUSIONS

The WMF and PRF greatly influenced power Doppler quantification, mainly when flow velocities lower than 20 cm/s were used. Although the experiments were conducted in a nonclinical environment, the evaluated parameters are equivalent to those used in clinical practice, which makes them valuable for aiding the interpretation of related data in future research.

Three-Dimensional Power Doppler Vascularization in Women With Ovarian Endometriomas and Relationship With Associated Painful Symptoms

OBJECTIVES

The objective of the study was to evaluate the correlation between endometrioma-associated pain and lesion vascularization as measured with 3-dimensional power Doppler transvaginal sonography.

METHODS

Endometriomas were examined, and 4 indices were obtained: mean grayness, flow index, vascularization index, and vascularization-flow index. Dysmenorrhea, chronic pelvic pain, and dyspareunia were analyzed in terms of severity, presence/absence, and duration.

RESULTS

Twenty-nine women were selected. The univariable association of painful symptoms in terms of presence/absence and duration was low with the exception of mean grayness with the presence of chronic pelvic pain (β = -0.106; P = .047; 95% confidence interval, 0.810 to 0.998). The R² value increased to 0.226 for dysmenorrhea (β = -0.475; P = .029) when analyzing the association between the vascularization index and the severity of painful symptoms. The visual analog scale scores for chronic pelvic pain and dyspareunia were higher (R²  = 0.300; β = -0.547 and -0.548, respectively; P = .028 and .053).

CONCLUSIONS

We observed an inverse association between the severity of pain and endometrioma vascularization. Further larger studies are required to confirm our findings.

Three dimensional power Doppler of the placenta and its clinical applications

The aim of this review is to discuss three dimensional (3D) power Doppler of the placenta and its clinical applications. There is a strong clinical need to develop noninvasive, simple and widely available methods of evaluating in vivo placental function to assess fetal wellbeing. While conventional ultrasound is a proven tool in the evaluation of fetal structural anomalies and health, its ability to assess placental function, especially prior to the onset of fetal compromise, is the subject of ongoing investigation. Three dimensional power Doppler has the ability to detect vascularity and blood flow with greater detail than conventional ultrasound, which has led to its investigation in preeclampsia, fetal growth restriction, and other placental vascular abnormalities. While more data are needed on the optimal imaging protocol and its predictive ability for clinical outcomes, 3D power Doppler is emerging as a promising new technology that will improve the evaluation of placental function.

3D power Doppler in uterine fibroids; influence of gain, cardiac cycle and off-line measurement techniques

This study answers the question of whether ultrasound machine settings and the cardiac cycle can influence 3D power Doppler (3D PD) indices in the evaluation of uterine fibroid vascularisation. These parameters were reported to affect the vascular indices and cause undesired variation. 3D PD ultrasound was performed using three different gain settings: a fixed predetermined gain (50 dB), a higher gain (65 dB) and an individualised subjectively most optimal gain. Two consecutive 3D PD sweeps were taken to evaluate the effect of the cardiac cycle. A predetermined most optimal fixed gain setting was not different from the individually most optimal chosen gain in vascular assessment of fibroids. A higher gain corresponded with a significantly higher vascular index (VI). Potential variation during the cardiac cycle does not disturb the VI in fibroids.

Fibroid vascularisation assessed with three-dimensional power Doppler ultrasound is a predictor for uterine fibroid growth: a prospective cohort study

OBJECTIVE

To analyse fibroid vascularisation measured with three-dimensional (3D) power Doppler in relation to absolute fibroid volume change during 12 months of follow up and in relation to fibroid growth rate per year.

DESIGN

A prospective cohort study was performed between March 2012 and March 2014.

SETTING

Outpatient clinic of the VU medical centre, Amsterdam.

POPULATION OR SAMPLE

All premenopausal women diagnosed with a maximum of two fibroids with expectant management were consecutively included.

METHODS

Three-dimensional ultrasound including power Doppler was performed at baseline, 3, 6 and 12 months. Volume and vascular parameters were calculated using VOCAL software.

MAIN OUTCOME MEASURES

The relationship between vascular index (VI) at baseline and fibroid volume over time was analysed using linear mixed model analyses for repeated measurements. Second, the relationship between VI at baseline and fibroid growth rate per year was calculated using linear regression analyses. Analyses were adjusted for possible confounders.

RESULTS

In all, 66 women (mean age 42 years) completed 12 months of follow up without treatment. Baseline fibroid vascularisation (VI) measured with 3D power Doppler is correlated with fibroid volume at 12 months (P = 0.02 ). An increase of 1% in VI at baseline was associated with a 7.00-cm³ larger fibroid volume at 12 months. Furthermore, vascularisation was also associated with fibroid growth rate per year (P = 0.04).

CONCLUSION

In women with uterine fibroids without therapy, baseline vascularisation (VI) measured with 3D power Doppler is correlated with absolute fibroid volume change at 12 months and with fibroid growth rate per year.

TWEETABLE ABSTRACT

Fibroid vascularisation correlates with absolute fibroid volume change and fibroid growth rate per year.

Short-Term Exposure to Urban Air Pollution and Influences on Placental Vascularization Indexes

BACKGROUND

It has been widely demonstrated that air pollution can affect human health and that certain pollutant gases lead to adverse obstetric outcomes, such as preeclampsia and fetal growth restriction.

OBJECTIVES

We evaluated the influence of individual maternal exposure to air pollution on placental volume and vascularization evaluated in the first trimester of pregnancy.

METHODS

This was a cross-sectional study on low-risk pregnant women living in São Paulo, Brazil. The women carried passive personal NO₂ and O₃ monitors in the week preceding evaluation. We employed the virtual organ computer-aided analysis (VOCAL) technique using three-dimensional power Doppler ultrasound to evaluate placental volume and placental vascular indexes [vascularization index (VI), flow index (FI), and vascularization flow index (VFI)]. We analyzed the influence of pollutant levels on log-transformed placental vascularization and volume using multiple regression models.

RESULTS

We evaluated 229 patients. Increased NO₂ levels had a significant negative association with log of VI (p = 0.020 and beta = -0.153) and VFI (p = 0.024 and beta = -0.151). NO₂ and O₃ had no influence on the log of placental volume or FI.

CONCLUSIONS

NO₂, an estimator of primary air pollutants, was significantly associated with diminished VI and VFI in the first trimester of pregnancy.

Assessment of the uterus with three-dimensional ultrasound in women undergoing ART

BACKGROUND

A detailed assessment of the uterus forms a pivotal part of the ART treatment process. The emergence of three-dimensional ultrasound (3D US) has provided clinicians with a highly powerful tool in this respect. Assessments with 3D US range from the reconstruction of anatomical planes elusive to conventional US, to the objective measurement of anatomical volumes and vascularization parameters. However, despite the ever increasing number of publications emerging in the literature, the question of which aspects of 3D US are of most clinical value remains a topic of debate.

OBJECTIVE AND RATIONALE

The objective of this review is to dissect which aspects of the 3D US assessment of the uterus are supported by a strong level of evidence to date, and should therefore be incorporated into current routine clinical practice.

SEARCH METHODS

We conducted a systematic search of the PubMed database up to May 2016, using a combination of text words and Medical Subject Headings (MeSH) pertaining to the 3D US assessment of the uterus. All articles published in the English language were screened to ascertain relevance to women of reproductive age; further citations were retrieved through manual reference list searching.

OUTCOMES

A multitude of predominantly observational studies were identified, which concerned a vast variety of 3D US uterine assessments. All articles unequivocally praised the non-invasive, cost-effective, highly acceptable and objective nature of 3D US. Studies regarding the value of assessing the endometrial volume and vascularization prior to embryo transfer appeared conflicting and inconsistent. Studies regarding the imaging of uterine pathology and identification of intratubal and intrauterine devices consistently reported high rates of diagnostic accuracy. A recent RCT did not show an improvement in clinical outcomes when comparing 3D versus 2D US during embryo transfer. However, preliminary studies suggested that 3D US is superior in determining the site of implantation, particularly in ambiguous cases such as interstitial and angular pregnancies. Finally, pilot studies have suggested that the further integration of 3D and possibly 4D US with surgical interventions of the uterus may be a promising prospect.

WIDER IMPLICATIONS

3D US may prove to be an invaluable tool in the assessment of the uterus within the context of ART. Currently, the aim should be to highlight the aspects of 3D US that are most evidence-based and valuable for patients, and to incorporate these into routine clinical practice.

Past, present and future ultrasonographic techniques for analyzing ovarian masses

Ultrasonography is today the method of choice for distinguishing between benign and malignant adnexal pathologies. Using pattern recognition several types of tumors can be recognized according to their characteristic appearance on gray-scale imaging. Color Doppler imaging should be used only to perform a semiquantitative color score or evaluate the flow location. International Ovarian Tumor Analysis group had standardized definitions characterizing adnexal masses and suggested the use of 'simple rules' in premenopausal women. Recently, the use of 3D vascular indices has been proposed but its potential use in clinical practice is debated. Also computerized aided diagnosis algorithms showed encouraging results to be confirmed in the future.

Sonographic evaluation of polycystic ovaries

The morphological features of the ovaries in women with polycystic ovary syndrome (PCOS) have been well described by ultrasound imaging technology. These include enlarged ovary size, multiple small follicles of similar size, increased ovarian stromal volume and echogenicity, peripheral distribution of the follicles, and higher stromal blood flow. Ultrasound identification of the presence of polycystic ovarian morphology (PCOM) has been recognized as a component of PCOS diagnosis. With the advance of ultrasound technology, new definition has been proposed recently. There is, however, a paucity of data for the ovarian morphology in normal and PCOS adolescents. Magnetic resonance imaging has the potential to be an alternative imaging modality for diagnosing PCOM in adolescence.

Utero-placental vascularisation in normal and preeclamptic and intra-uterine growth restriction pregnancies: third trimester quantification using 3D power Doppler with comparison to placental vascular morphology (EVUPA): a prospective controlled study

INTRODUCTION

Preeclampsia (PE) and intra-uterine growth restriction (IUGR) are two major pregnancy complications related to chronic utero-placental hypoperfusion. Three-dimensional power Doppler (3DPD) angiography has been used for the evaluation of utero-placental vascularisation and three vascular indices have been calculated: the vascularisation index (VI), flow index (FI) and vascularisation-FI (VFI). However, several technical endpoints hinder the clinical use of 3DPD as physical characteristics and machine settings may affect 3DPD indices, and so its clinical significance is not yet clear.

OBJECTIVES

The primary objective is to better understand the clinical significance of 3DPD indices by evaluating the relationship between these indices and placental morphometry. Secondary objectives are (i) to determine the impact of machine settings and physical characteristics on 3DPD indices, and (ii) to evaluate physio-pathological placental vascularisation patterns.

METHODS AND ANALYSIS

This is a prospective controlled study. We expect to include 112 women: 84 with normal pregnancies and 28 with PE and/or IUGR (based on our former cohort study on 3DPD indices for PE and/or IUGR prediction (unpublished data)). Within 72 h before planned or semi-urgent caesarean section, utero-placental 3DPD images with five different machine settings will be acquired. Placentas will be collected and examined after surgery and stereological indices (volume density, surface density, length density) calculated. The 3DPD indices (VI, FI and VFI) of the placenta and adjacent myometrium will be calculated. Correlation between Doppler and morphological indices will be evaluated by Pearson or Spearman tests. Agreement between 3DPD indices and morphological indices will be assessed by Bland and Altman plots. The impact of Doppler settings and maternal characteristics on 3DPD indices will be evaluated with a multivariate linear regression model.

ETHICS

The study and related consent forms have been approved by the French Ethics Committee (CPP, Comité de Protection des Personnes) Est III on 4 March 2014.

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

OBJECTIVES

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.

METHODS

We acquired 11 STIC data sets, 1 for each PRF value ranging from 0.6 to 9.0 kHz. Vascularization-flow index and volumetric PI values were determined from the 440 static 3D data sets contained in these STIC data sets. Additionally, 3 sets of radio-frequency data were acquired for offline processing of different wall motion filter values for PRF values of 0.6, 3.3, and 10 kHz.

RESULTS

We constructed VFI curves and observed 2 patterns: a flattened pattern with a low PRF and a triphasic pattern with a high PRF, correlating with the known pulsed wave Doppler profile of this vessel. Volumetric PI values were around 0 for low PRF settings and increased with increasing PRF. Analysis of the radiofrequency data showed that increasing wall motion filter values gradually filtered out the low-velocity power Doppler signals while retaining the higher-velocity ones, allowing the distinction of integrated power Doppler signal velocity throughout the cardiac cycle.

CONCLUSIONS

We conclude that the PRF and wall motion filter dramatically influence 3D power Doppler indices and the volumetric PI, and the use of PRF values in which minimum VFI values are measured during the diastolic phase in the spectral Doppler wave may validate the use of the volumetric PI.

Influence of ulipristal acetate therapy compared with uterine artery embolization on fibroid volume and vascularity indices assessed by three-dimensional ultrasound: prospective observational study

OBJECTIVE

To compare the effects of two alternative treatment options for uterine fibroids, ulipristal acetate (UPA) and uterine artery embolization (UAE), on fibroid volume and vascularity at 3-month follow-up.

METHODS

Premenopausal patients with symptomatic, intramural uterine fibroids were included in this prospective case-control study. Seventeen patients who qualified for preoperative UPA treatment were pair-matched with patients of similar age (± 5 years) and fibroid volume (± 10% of volume) who qualified for UAE. Patients undergoing UPA treatment received 5 mg/24 h of oral UPA for 3 months. UAE was performed in patients bilaterally by an interventional radiologist. To estimate dominant fibroid volume, Virtual Organ Computer-aided AnaLysis (VOCAL™) was used. The VOCAL program was also used to calculate three-dimensional power Doppler vascular indices: vascularization index (VI), flow index (FI) and vascularization flow index (VFI). Dominant fibroid volumes and VI, FI and VFI values were assessed before commencement of UPA treatment or UAE procedure and again at 3 months afterwards.

RESULTS

In both the UPA and UAE groups, fibroid volumes decreased significantly after treatment in comparison with baseline volumes obtained prior to treatment. The percentage of fibroid volume reduction after 3 months of UPA therapy (48.1%) was not significantly different from the reduction seen 3 months after the UAE procedure (47.3%). All vascular indices decreased significantly after treatment by UPA or UAE. The percentage reduction in VI and VFI 3 months after UAE (95.4% for both) was significantly greater than the percentage reduction in patients after 3 months of UPA therapy (51.5% and 62.5%, respectively); however the difference in FI reduction between treatment groups did not reach significance (54.3% for UAE and 30.9% for UPA). No significant side-effects were observed in either treatment group.

CONCLUSIONS

Fibroid treatment by UPA therapy results in a decrease in fibroid volume, comparable with that after UAE, and decreases fibroid vascularization, although to a lesser extent than does UAE.

Two- and three-dimensional transvaginal ultrasound with power Doppler angiography and gel infusion sonography for diagnosis of endometrial malignancy

OBJECTIVES

To evaluate the diagnostic efficiency of two-dimensional (2D) and three-dimensional (3D) transvaginal ultrasonography, power Doppler angiography (PDA) and gel infusion sonography (GIS) at offline analysis for recognition of malignant endometrium compared with real-time evaluation during scanning, and to determine optimal image parameters at 3D analysis.

METHODS

One hundred and sixty-nine consecutive women with postmenopausal bleeding and endometrial thickness ≥ 5 mm underwent systematic evaluation of endometrial pattern on 2D imaging, and 2D videoclips and 3D volumes were later analyzed offline. Histopathological findings at hysteroscopy or hysterectomy were used as the reference standard. The efficiency of the different techniques for diagnosis of malignancy was calculated and compared. 3D image parameters, endometrial volume and 3D vascular indices were assessed. Optimal 3D image parameters were transformed by logistic regression into a risk of endometrial cancer (REC) score, including scores for body mass index, endometrial thickness and endometrial morphology at gray-scale and PDA and GIS.

RESULTS

Offline 2D and 3D analysis were equivalent, but had lower diagnostic performance compared with real-time evaluation during scanning. Their diagnostic performance was not markedly improved by the addition of PDA or GIS, but their efficiency was comparable with that of real-time 2D-GIS in offline examinations of good image quality. On logistic regression, the 3D parameters from the REC-score system had the highest diagnostic efficiency. The area under the curve of the REC-score system at 3D-GIS (0.89) was not improved by inclusion of vascular indices or endometrial volume calculations.

CONCLUSION

Real-time evaluation during scanning is most efficient, but offline 2D and 3D analysis is useful for prediction of endometrial cancer when good image quality can be obtained. The diagnostic efficiency at 3D analysis may be improved by use of REC-scoring systems, without the need for calculation of vascular indices or endometrial volume. The optimal imaging modality appears to be real-time 2D-GIS.

Role of 3-D ultrasound in clinical obstetric practice: evolution over 20 years

The use of 3-D ultrasound in obstetrics has undergone dramatic development over the past 20 years. Since the first publications on this application in clinical practice, several 3-D ultrasound techniques and rendering modes have been proposed and applied to the study of fetal brain, face and cardiac anatomy. In addition, 3-D ultrasound has improved calculations of the volume of fetal organs and limbs and estimations of fetal birth weight. And furthermore, angiographic patterns of fetal organs and the placenta have been assessed using 3-D power Doppler ultrasound quantification. In this review, we aim to summarize current evidence on the clinical relevance of these methodologies and their application in obstetric practice.

Performance of three-dimensional power Doppler angiography as third-step assessment in differential diagnosis of adnexal masses

OBJECTIVE

To evaluate the contribution of three-dimensional (3D) power Doppler angiography (3D-PDA) to the differential diagnosis of adnexal masses.

METHODS

This was a prospective study in women diagnosed with a persistent adnexal mass and subsequently scheduled for surgery in a tertiary university hospital. All women were evaluated by transvaginal/transrectal ultrasound according to a predetermined three-step protocol, with transabdominal ultrasound being performed in some cases. First, morphological evaluation of the mass was performed using gray-scale 'pattern recognition' (first step). Lesions diagnosed as having a benign pattern were considered as being at low risk of malignancy whereas tumors with solid components, ascites and/or signs of carcinomatosis were considered as being at high risk of malignancy. In both cases no further test was performed and a decision regarding clinical management, either for follow-up or surgery, was taken. Tumors with solid components but without signs of ascites or carcinomatosis were considered as being at intermediate risk of malignancy. These lesions were assessed by two-dimensional (2D) PDA to evaluate tumor vascularity (color score) (second step). Solid tumors with a color score of 1 or 2 were considered as benign and no further test was performed, while tumors with a color score of 2, 3 or 4 within solid components or a color score of 3 or 4 in the case of a solid tumor were considered as malignant. The latter group underwent 3D-PDA assessment (third step). Vascularization index (VI) was calculated in a 1-mL sphere of the most vascularized area of the tumor. When a VI ≥ 24.015% was found, the tumor was considered as malignant. All masses were removed surgically and definitive histological diagnosis was used as the gold standard. Sensitivity and specificity for each strategy were calculated and compared. In the case of bilateral tumors, only the more suspicious one was used for analysis.

RESULTS

A total of 367 adnexal masses diagnosed in 367 women (mean age, 46.5 (range, 18-80) years) were evaluated during the study period. Of these, 86 masses were malignant and 281 were benign. The sensitivity and specificity for each assessment strategy were as follows: one-step, 97.7% and 78.6%; two-step, 94.2% and 97.9% (P < 0.001 for specificity when compared with that of one-step); three-step, 90.7% and 98.9% (not statistically significant when compared with that of two-step).

CONCLUSIONS

The addition of 2D-PDA in the differential diagnosis of an adnexal mass significantly increases specificity while sensitivity remains high; however performing subsequent 3D-PDA does not provide additional information or further improve diagnostic performance subsequent to 2D-PDA.

Can 3D power Doppler identify levator ani vascularization at its pubic insertion?

INTRODUCTION AND HYPOTHESIS

The levator ani is the most important muscle in the pelvic floor. This pilot study using 3D power Doppler aimed to identify normal vascularization of the puborectalis/pubovisceralis muscle at its insertion in nulliparous and premenopausal women.

METHODS

Forty nulliparous and premenopausal women were evaluated at the Gynecological Unit of a tertiary hospital. All women underwent a translabial ultrasound (US) with 3D power Doppler. Pubic insertion of the puborectalis/pubovisceralis muscle was assessed in the axial plane, and vascularization index (VI), flow index (FI), and vascularization-flow index (VFI) were calculated bilaterally. Volumes were analyzed offline by two independent observers, and interobserver agreement and correlation between variables was calculated.

RESULTS

A high, statistically significant, correlation was found between the three US indices on each side (p < 0.005). No correlation was found between the US index and either of the demographic parameters of body mass index [(BMI), p > 0.241], or age (p > 0.398). The degree of correlation between the same index on the different sides was not statistically significant.

CONCLUSION

Puborectalis/pubovisceralis muscle vascularization at its insertion can be identified using 3D Doppler US, but values differ substantially from those of the contralateral side.

Calibrating Doppler imaging of preterm intracerebral circulation using a microvessel flow phantom

Introduction: Preterm infants are born during critical stages of brain development, in which the adaptive capacity of the fetus to extra-uterine environment is limited. Inadequate brain perfusion has been directly linked to preterm brain damage. Advanced high-frequency ultrasound probes and processing algorithms allow visualization of microvessels and depiction of regional variation. To assess whether visualization and flow velocity estimates of preterm cerebral perfusion using Doppler techniques are accurate, we conducted an in vitro experiment using a microvessel flow phantom.

Materials and Methods: An in-house developed flow phantom containing two microvessels (inner diameter 200 and 700 μm) with attached syringe pumps, filled with blood-mimicking fluid, was used to generate non-pulsatile perfusion of variable flow. Measurements were performed using an Esaote MyLab70 scanner.

Results: Microvessel mimicking catheters with velocities as low as 1 cm/s were adequately visualized with a linear ultrasound probe. With a convex probe, velocities <2 cm/s could not be depicted. Within settings, velocity and diameter measurements were highly reproducible [intra-class correlation 0.997 (95% CI 0.996–0.998) and 0.914 (0.864–0.946)]. Overall, mean velocity was overestimated up to threefold, especially in high velocity ranges. Significant differences were seen in velocity measurements when using steer angle correction and in vessel diameter estimation (p < 0.05).

Conclusion: Visualization of microvessel-size catheters mimicking small brain vessels is feasible. Reproducible velocity and diameter results can be obtained, although important overestimation of the values is observed. Before velocity estimates of microcirculation can find its use in clinical practice, calibration of the ultrasound machine for any specific Doppler purpose is essential. The ultimate goal is to develop a sonographic tool that can be used for objective study of regional perfusion in routine practice.

Second-trimester placental volume and vascular indices in the prediction of small-for-gestational-age neonates

OBJECTIVE

To evaluate the ability of second-trimester placental volume and vascular indices to predict small-for-gestational-age (SGA) birth weight pregnancies.

MATERIAL AND METHODS

Women with singleton pregnancies were prospectively evaluated at 17-20 weeks of gestation. Second-trimester placental volume and vascular indices were obtained and calculated using volume organ computer-aided analysis and three-dimensional (3D) power Doppler ultrasound. Participants were followed until delivery and their medical records were reviewed, including maternal age, parity and pregestational body weight and body height, as well as the gestational age, birth weight and gender of the fetus.

RESULTS

Of the 163 women with complete follow-up, 20 gave birth to SGA and 143 to appropriate-for-gestational-age (AGA) neonates. The mean second-trimester placental volume was significantly lower in the SGA than in the AGA group (170.6 ± 49.8 vs. 213.5 ± 75.8 cm(3), p = 0.015). None of the vascular indices, including the vascularization index, flow index and vascularization flow index, differed significantly between the two groups. We also found that the optimum cutoff for placental volume at a gestational age of 17-18 weeks was 189.7 cm(3).

DISCUSSION

Second-trimester placental volume was positively correlated with neonatal birth weight. Second-trimester placental volume measured on 3D ultrasound may be predictive of SGA neonates.

[Placental 3D Doppler angiography: current and upcoming applications]

The placental dysfunction, which seems to be caused by a defect of trophoblastic invasion and impaired uterine vascular remodeling since the first trimester, is responsible in a non-exclusive way for the chronic placental hypoxia, resulting secondarily in the intra-uterine growth restriction (IUGR) and/or pre-eclampsia (PE). The quality of utero-placental vasculature is essential for a proper fetal development and a successful progress of pregnancy. However, the in vivo assessment of placental vascularization with non-invasive methods is complicated by the small size of placental terminal vessel and its complex architecture. Moreover, imaging with contrast agent is not recommended to pregnant women. Until recently, the fetal and maternal vascularization could only be evaluated through pulse Doppler of uterine arteries during pregnancy, which has little clinical value for utero-placental vascularization defects assessment. Recently, a non-invasive study, without use of contrast agent for vasculature evaluation of an organ of interest has become possible by the development of 3D Doppler angiography technique. The objective of this review was to make an inventory of its current and future applications for utero-placental vasculature quantification. The main findings of the literature on the assessment of utero-placental vascularization in physiological situation and major placental vascular dysfunction pathologies such as PE and IUGR were widely discussed.

Early pregnancy placental bed and fetal vascular volume measurements using 3-D virtual reality

In this study, a new 3-D Virtual Reality (3D VR) technique for examining placental and uterine vasculature was investigated. The validity of placental bed vascular volume (PBVV) and fetal vascular volume (FVV) measurements was assessed and associations of PBVV and FVV with embryonic volume, crown-rump length, fetal birth weight and maternal parity were investigated. One hundred thirty-two patients were included in this study, and measurements were performed in 100 patients. Using V-Scope software, 100 3-D Power Doppler data sets of 100 pregnancies at 12 wk of gestation were analyzed with 3D VR in the I-Space Virtual Reality system. Volume measurements were performed with semi-automatic, pre-defined parameters. The inter-observer and intra-observer agreement was excellent with all intra-class correlation coefficients >0.93. PBVVs of multiparous women were significantly larger than the PBVVs of primiparous women (p = 0.008). In this study, no other associations were found. In conclusion, V-Scope offers a reproducible method for measuring PBVV and FVV at 12 wk of gestation, although we are unsure whether the volume measured represents the true volume of the vasculature. Maternal parity influences PBVV.

Hepatic portal vein flow and three dimensional indices of hepatic perfusion in pre-eclampsia compared with normal pregnancy

It has been suggested that the origins of pre-eclampsia arise from the maternal venous system dysfunction. This study aimed to test this hypothesis by assessing hepatic perfusion in pre-eclampsia using three-dimensional (3D) ultrasound. The hepatic portal vein flow in 12 women with normal pregnancy and 11 women with pre-eclampsia was measured using standard Doppler ultrasound. The 3D indices of hepatic perfusion: flow index (FI), vascular index (VI) and vascularisation flow index (VFI), which are believed to reflect vascularity and flow intensity were also measured. Because of small numbers, a non-parametric test was used to test differences between groups. Hepatic portal vein flow was no different between women with normal pregnancy compared with women with pre-eclampsia (228.1 (215.5-270.6) vs. 283.0 (145.9-344.6); p = 0.90). The 3D indices of hepatic perfusion were as follows (FI: 36.3(30.7-42.5) vs. 39.7 (27.7-44.2), p = 1.00; VI: 11.7 (3.6-21.2) vs. 3.0 (0.5-7.6), p = 0.04; VFI: 4.7 (1.2-8.3) vs. 1.2 (0.1-3.2), p = 0.06, respectively). This study was not able to support or refute the suggestion that the genesis of pre-eclampsia arises from the maternal venous circulation. There may be biological differences in the 3D indices of hepatic perfusion in women with pre-eclampsia compared with normal pregnant women.

Selection of the sub-noise gain level for acquisition of VOCAL data sets: a reliability study

This study was aimed at assessing the intra-observer and inter-observer repeatability of selecting the sub-noise gain (SNG) level when acquiring placental volumes with 3-D power Doppler for analysis using virtual organ computer-aided analysis (VOCAL). Sixty women with uncomplicated singleton pregnancies between 20 and 38 wk of gestation were recruited. Two women were excluded for flash artifact noted during image analysis. Two blinded observers independently adjusted gain to their perceived SNG level before acquiring a static 3-D volume of the placenta at the cord insertion; observers alternated after each acquisition until each had acquired two volumes. A single observer operated the probe at all times. During offline analysis, SNG levels were recorded and VOCAL indices were calculated. SNG exhibited excellent intra-observer and inter-observer reliability. Intra-observer intra-class correlation coefficients (95% confidence intervals) were 0.98 (0.97-0.99) and 0.98 (0.98-0.99) for observers 1 and 2, respectively. The inter-observer intra-class correlation coefficient was 0.96 (0.93-0.98). Despite its perceived inherent subjectivity, the excellent intra-class correlation coefficients obtained in this study support SNG as a promising tool for future research using 3-D power Doppler.

Quantitative assessment of placental vasculature and placental volume in normal pregnancies with the use of 3D Power Doppler

PURPOSE

The aim of the study was to determine reference values for placental vascular indices and placental volume according to gestational age.

MATERIAL/METHODS

The assessment of placental vascular indices and placental volume using 3D Power Doppler and the Virtual Organ Computer-aided Analysis (VOCAL) technique was performed on 100 normal fetuses between 22 and 41 weeks of gestation. In this study the method of the individual setting of the power Doppler gain value was used. Only patients with entirely visualized placenta were included in the study.

RESULTS

No statistically relevant difference in the values of placental vascular indices and placental volume between different localizations of the placenta was detected. No statistically significant changes to placental vascular indices depending on gestational age were found. It enabled to determine the 10th, 50th and 90th percentile values for the vascularization index (VI), flow index (FI), vascularization-flow index (VFI), which are independent of gestational age. No correlation was found between placental volume and placental vascular indices.

CONCLUSIONS

The values of placental vascular indices are constant between the 22nd and 41st week of a normal pregnancy. Placental volume measured with the use of the VOCAL program increases between 22nd and 41st week of a normal pregnancy. In a normal pregnancy the placental vasculature increases adequately to the increase of its volume. The method of the individual setting of the power Doppler gain value makes it possible to achieve comparable values of placental vascular indices regardless of the distance between the probe and the placenta.

MANAGEMENT OF REDUCED FETAL MOVEMENTS

Reduced fetal movement (RFM) is commonly defined as any reduction in maternal perception of fetal activity. Perceived fetal activity may be movement of limbs, trunk or head movement, but excludes fetal hiccoughs (as this is involuntary movement). The perception of fetal movement by an expectant mother is the first, and ongoing, non-sonographic indicator of fetal viability. The “normal” pattern of fetal movements varies from pregnancy to pregnancy, and often does not become established until 28 weeks’ gestation. Many babies have particularly active periods of the day, usually corresponding to periods of maternal rest and inactivity (which may in itself reflect increased maternal awareness of fetal movement). A variable percentage of sonographically observed fetal movements are perceived by prospective mothers (commonly 30–40%, although some studies report rates as high as 80%).

Assessing repeatability of 3D Doppler indices obtained by static 3D and STIC power Doppler: a combined in-vivo/in-vitro flow phantom study

OBJECTIVES

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.

METHODS

The study was divided into two parts: in the first part (the in-vitro model) we scanned a flow phantom, while in the second part (the in-vivo model) we scanned a common carotid artery. Conventional static 3D and STIC-PD datasets were alternately acquired from these two models. VFI values were assessed from 0.38-cm(3) spherical samples of the main flow region in the static 3D datasets and in every frame of the STIC datasets. The variance of the minimum, mean and maximum VFI values from each STIC dataset was compared with the variance of VFI values from the static 3D datasets.

RESULTS

Ten static 3D and 10 STIC datasets were acquired from each model. Analysis of the in-vitro and in-vivo models showed a significant reduction in the variance of VFI values obtained using STIC as compared to static datasets. Additionally, we observed that the curves formed by VFI values obtained from successive frames in each STIC dataset were consistent across different datasets and that they resembled the waveforms obtained by spectral Doppler in both models.

CONCLUSIONS

3D-PD indices derived from STIC are more stable than those obtained from conventional static 3D-PD datasets. The curves of VFI throughout a reconstructed cardiac cycle using STIC are repeatable and resemble those obtained by spectral Doppler analysis of the vessel.

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.

Design of anthropomorphic flow phantoms based on rapid prototyping of compliant vessel geometries

Anatomically realistic flow phantoms are essential experimental tools for vascular ultrasound. Here we describe how these flow phantoms can be efficiently developed via a rapid prototyping (RP) framework that involves direct fabrication of compliant vessel geometries. In this framework, anthropomorphic vessel models were drafted in computer-aided design software, and they were fabricated using stereolithography (one type of RP). To produce elastic vessels, a compliant photopolymer was used for stereolithography. We fabricated a series of compliant, diseased carotid bifurcation models with eccentric stenosis (50%) and plaque ulceration (types I and III), and they were used to form thin-walled flow phantoms by coupling the vessels to an agar-based tissue-mimicking material. These phantoms were found to yield Doppler spectrograms with significant spectral broadening and color flow images with mosaic patterns, as typical of disturbed flow under stenosed and ulcerated disease conditions. Also, their wall distension behavior was found to be similar to that observed in vivo, and this corresponded with the vessel wall's average elastic modulus (391 kPa), which was within the nominal range for human arteries. The vessel material's acoustic properties were found to be sub-optimal: the estimated average acoustic speed was 1801 m/s, and the attenuation coefficient was 1.58 dB/(mm·MHz(n)) with a power-law coefficient of 0.97. Such an acoustic mismatch nevertheless did not notably affect our Doppler spectrograms and color flow image results. These findings suggest that phantoms produced from our design framework have the potential to serve as ultrasound-compatible test beds that can simulate complex flow dynamics similar to those observed in real vasculature.

Inapplicability of fractional moving blood volume technique to standardize Virtual Organ Computer-aided AnaLysis indices for quantified three-dimensional power Doppler

OBJECTIVE

To determine whether the technique of fractional moving blood volume (FMBV) is applicable to Virtual Organ Computer-aided AnaLysis II (VOCAL II™)-based indices to quantify three-dimensional power Doppler ultrasound (3D-PDU) by investigating the effect of gain level on the indices measured at a possible reference point for standardization.

METHODS

Ten women with singleton pregnancy between 33+3 and 37+5 weeks' gestation were recruited. The optimal position for 3D acquisition of cord insertion into the placenta was identified and static 3D-PDU volumes were acquired using consistent machine configurations. Without moving the probe or the participant changing position, successive 3D volumes were stored at -3, -5, -7 and -9 dB and at the individualized sub-noise gain (SNG) level. Volumes were excluded if flash artifact was present, in which case all five volumes were reacquired. Using 4D View software, the cord insertion was magnified and the smallest sphere possible was used to measure vascularization index (VI), flow index (FI) and vascularization flow index (VFI). The associations between VOCAL indices and gain level were assessed using Pearson's correlation coefficient.

RESULTS

VOCAL indices for cord insertion correlated poorly with gain level, whether fundamental or relative to SNG level (R(2) = 0.07 and 0.04, respectively). VI was consistently 100% and mean FI and VFI were 99.5 (SD, 0.57), with all values > 97 irrespective of gain level.

CONCLUSIONS

Whilst previous work has shown that gain correlates well with placental tissue VOCAL indices, the correlation between gain level and VOCAL indices in an area of 100% vascularity at the cord insertion is poor. Regions of 100% vascularity appear to be artificially assigned a value approaching 100% for all VOCAL indices irrespective of gain level. This precludes using the technique of VOCAL indices from large vessels to standardize power Doppler measurements and the FMBV index is therefore not applicable to image analysis using VOCAL.