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

Quantification of primary mitral regurgitation by echocardiography: A practical appraisal

The accurate quantification of primary mitral regurgitation (MR) and its consequences on cardiac remodeling is of paramount importance to determine the best timing for surgery in these patients. The recommended echocardiographic grading of primary MR severity relies on an integrated multiparametric approach. It is expected that the large number of echocardiographic parameters collected would offer the possibility to check the measured values regarding their congruence in order to conclude reliably on MR severity. However, the use of multiple parameters to grade MR can result in potential discrepancies between one or more of them. Importantly, many factors beyond MR severity impact the values obtained for these parameters including technical settings, anatomic and hemodynamic considerations, patient's characteristics and echocardiographer' skills. Hence, clinicians involved in valvular diseases should be well aware of the respective strengths and pitfalls of each of MR grading methods by echocardiography. Recent literature highlighted the need for a reappraisal of the severity of primary MR from a hemodynamic perspective. The estimation of MR regurgitation fraction by indirect quantitative methods, whenever possible, should be central when grading the severity of these patients. The assessment of the MR effective regurgitant orifice area by the proximal flow convergence method should be used in a semi-quantitative manner. Furthermore, it is crucial to acknowledge specific clinical situations in MR at risk of misevaluation when grading severity such as late-systolic MR, bi-leaflet prolapse with multiple jets or extensive leak, wall-constrained eccentric jet or in older patients with complex MR mechanism. Finally, it is debatable whether the 4-grades classification of MR severity would be still relevant nowadays, since the indication for mitral valve (MV) surgery is discussed in clinical practice for patients with 3+ and 4+ primary MR based on symptoms, specific markers of adverse outcome and MV repair probability. Primary MR grading should be seen as a continuum integrating both quantification of MR and its consequences, even for patients with presumed “moderate” MR.

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.

Function and Safety of SlowflowHD Ultrasound Doppler in Obstetrics

SlowflowHD is a new ultrasound Doppler imaging technology that allows visualization of flow within small blood vessels. In this mode, a proprietary algorithm differentiates between low-speed flow and signals attributed to tissue motion so that microvessel vasculature can be examined. Our objectives were to describe the low-velocity Doppler mode principles, to assess the bone thermal index (TIb) safety parameter in obstetric ultrasound scans and to evaluate adherence to professional guidelines. To achieve the latter goals, we retrospectively reviewed prospectively collected ultrasound images and video clips from pregnancy ultrasound scans at >10 wk of gestation over 4 mo. We used a custom-built optical character recognition-based software to automatically identify all images and video clips using this technology and extract the TIb. Overall, a total of 185 ultrasound scans performed by three fetal medicine physicians were included, of which 60, 54 and 71 scans were first-, second- and third-trimester scans, respectively. The mean (highest recorded) TIb values were 0.32 (0.70), 0.23 (0.70) and 0.32 (0.60) in the first, second, and third trimesters, respectively. Thermal index values were within recommended values set by the World Federation for Ultrasound in Medicine and Biology American Institute of Ultrasound in Medicine and British Medical Ultrasound Society in all scans.

Glycerol-in-SEBS gel as a material to manufacture stable wall-less vascular phantom for ultrasound and photoacoustic imaging

Styrene-ethylene/butylene-styrene (SEBS) copolymer-in-mineral oil gel is an appropriate tissue-mimicking material to manufacture stable phantoms for ultrasound and photoacoustic imaging. Glycerol dispersion has been proposed to further tune the acoustic properties and to incorporate hydrophilic additives into SEBS gel. However, this type of material has not been investigated to produce wall-less vascular flow phantom for these imaging modalities. In this paper, the development of a wall-less vascular phantom for ultrasound and photoacoustic imaging is reported. Mixtures of glycerol/TiO₂-in-SEBS gel samples were manufactured at different proportions of glycerol (10%, 15%, and 20%) and TiO₂(0% to 0.5%) to characterize their optical and acoustic properties. Optical absorption in the 500-950 nm range was independent of the amount of glycerol and TiO₂, while optical scattering increased linearly with the concentration of TiO₂. Acoustic attenuation and speed of sound were not influenced by the presence of TiO₂. The sample manufactured using weight percentages of 10% SEBS, 15% glycerol, and 0.2% TiO₂was selected to make the vascular phantom. The phantom proved to be stable during the pulsatile blood-mimicking fluid (BMF) flow, without any observed damage to its structure or leaks. Ultrasound color Doppler images showed a typical laminar flow, while the B-mode images showed a homogeneous speckled pattern due to the presence of the glycerol droplets in the gel. The photoacoustic images of the phantom showed a well-defined signal coming from the surface of the phantom and from the vessels where BMF was flowing. The Spearman's correlations between the photoacoustic and tabulated spectra calculated from the regions containing BMF, in this case a mixture of salt solutions (NiCl₂and CuSO₄), were higher than 0.95. Our results demonstrated that glycerol-in-SEBS gel was an adequate material to make a stable vascular flow phantom for ultrasound photoacoustic imaging.

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.

4D Doppler Ultrasound in High Grade Serous Ovarian Cancer Vascularity Evaluation-Preliminary Study

The aim of the study was to evaluate the usefulness of 4D Power Doppler tissue evaluation to discriminate between normal ovaries and ovarian cancer tumors. This was a prospective observational study. Twenty-three cases of surgically confirmed ovarian High Grade Serous Carcinoma (HGSC) were analyzed. The control group consisted of 23 healthy patients, each matching their study-group counterpart age wise (±3 years) and according to their menopausal status. Transvaginal Doppler 4D ultrasound scans were done on every patient and analyzed with 3D/4D software. Two 4D indices-volumetric Systolic/Diastolic Index (vS/D) and volumetric Pulsatility Index (vPI)-were calculated. To keep results standardized and due to technical limitations, virtual 1cc spherical tissue samples taken from the part with highest vascularization as detected by bi-directional Power Doppler were analyzed for both groups of ovaries. Values of volumetric S/D indices and volumetric PI indices were statistically lower in ovarian malignant tumors compared to normal ovaries: 1.096 vs. 1.794 and 0.092 vs. 0.558, respectively (p < 0.001). The 4D bi-directional Power Doppler vascular indices were statistically different between malignant tumors and normal ovaries. These findings could support the rationale for future studies for assessing this technology to discriminate between malignant and benign tumors.

Uterine and placental blood flow indexes and antinuclear autoantibodies in unexplained recurrent pregnancy loss: should they be investigated in pregnancy as correlated potential factors? A retrospective study

BACKGROUND

The potential role of antinuclear antibodies (ANA) in recurrent pregnancy loss (RPL) pathogenesis is still debated, although some evidences suggest that they could affect pregnancy outcome, leading to a higher miscarriage rate in these patients. A hypothesized mechanism is through changes in uterine flow in pre-conceptional stage, by modifying endometrial receptivity in RPL. However, scant data are available, in pregnancy, about their role in RPL placental perfusion, also in relation to its potential treatments, such as low molecular weight heparin (LMWH). The aim of this study is to retrospectively further investigate the correlation between two-dimensional (2D) and three-dimensional (3D) uterine and placental flow indexes and the presence or the absence of ANA in women with unexplained RPL (uRPL), treated or not treated with LMWH.

METHODS

2D Doppler measurement of pulsatility index (PI) of the uterine arteries and 3D ultrasonography determination of vascularization index (VI), flow index (FI) and vascularization flow index (VFI) was carried out with the aid of the virtual organ computer-aided analysis (VOCAL) technique in LMWH treated (n 24) and not treated-uRPL patients (n 20) and in the relative control group (n 27), each group divided in ANA+ and ANA- subgroups. Serum assay for the presence of ANA was performed in all women.

RESULTS

No differences were found in PI, VFI and VI values, by comparing the different groups. A difference in VI values was found for ANA- patients between RPL women not treated with LMWH and the treated ones (p = 0,01), which have lower VI values and similar to controls. By considering only ANA- treated and not treated RPL patients, the ROC curve shows an area of 0,80 and at the VI cut-off of 11,08 a sensitivity of 85% and a specificity of 67%.

CONCLUSIONS

LMWH could exert a potential beneficial effect in restoring the physiological blood flow supply in terms of VI in uRPL ANA- status, suggesting to include ANA and VI investigations in the RPL diagnostic algorithm in a research context, since further studies are needed to clarify this challenging hypothesis in order to try to ameliorate ANA and abnormal placental vascularization negative influence on RPL pregnancy outcome .

Placental Pulsatility: Quantitative Assessment of Placental Bed Vasculature by 2-Dimensional Doppler Cine Imaging

OBJECTIVES

Vascular resistance is known to be one of the determinants of pulsatile flow. This study aimed to investigate whether quantitative 2-dimensional Doppler ultrasound can capture and evaluate the pulsatility within the placental bed vasculature.

METHODS

The placental bed vasculature was imaged by directional power Doppler ultrasound. Ten-second cine clips were recorded by using standardized machine settings. A region of interest with a prominent Doppler signal in the uteroplacental interface was analyzed for the percentage of vascularity to generate a time-vascularity waveform. A vascular pulsatility index representing variation over the cardiac cycle was calculated by the ratio of the systolic-diastolic difference in vascularity to the mean vascularity. The acquisitions were repeated with 6 different pulse repetition frequencies (PRFs) and 3 wall motion filter (WMF) settings to evaluate their impact on the Doppler measurements.

RESULTS

Ten sets of cine clips were analyzed for this study. The pulsatile nature of the vascularity was readily apparent in each cine clip. The measured time-vascularity waveforms showed uniform cyclic variation in vascularity over the cardiac cycle, with systolic vascularity significantly higher than diastolic vascularity at each combination of PRF and WMF (P < .05). A gradual increase in the vascular pulsatility index was observed with an increasing PRF or WMF. Normalization of systolic-to-diastolic measurement provided a stable vascular assessment across the range of PRFs.

CONCLUSIONS

Doppler cine clips provide a dynamic representation of the placental bed vasculature and a novel analytic approach to quantitatively evaluating the pulsatility of this critical vascular network. Further work is warranted to explore the reproducibility and clinical potential of this approach.

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.