A systematic analysis of the feasibility of four-dimensional ultrasound imaging using spatiotemporal image correlation in routine fetal echocardiography

Deep Semi-Supervised Ultrasound Image Segmentation by Using a Shadow Aware Network With Boundary Refinement

Accurate ultrasound (US) image segmentation is crucial for the screening and diagnosis of diseases. However, it faces two significant challenges: 1) pixel-level annotation is a time-consuming and laborious process; 2) the presence of shadow artifacts leads to missing anatomy and ambiguous boundaries, which negatively impact reliable segmentation results. To address these challenges, we propose a novel semi-supervised shadow aware network with boundary refinement (SABR-Net). Specifically, we add shadow imitation regions to the original US, and design shadow-masked transformer blocks to perceive missing anatomy of shadow regions. Shadow-masked transformer block contains an adaptive shadow attention mechanism that introduces an adaptive mask, which is updated automatically to promote the network training. Additionally, we utilize unlabeled US images to train a missing structure inpainting path with shadow-masked transformer, which further facilitates semi-supervised segmentation. Experiments on two public US datasets demonstrate the superior performance of the SABR-Net over other state-of-the-art semi-supervised segmentation methods. In addition, experiments on a private breast US dataset prove that our method has a good generalization to clinical small-scale US datasets.

Area of the Fetal Ascending and Descending Aorta by Spatiotemporal Image Correlation in the Rendering Mode: Reproducibility and Comparison with Pregestational Diabetic Mothers

Background

The objective of this study was to assess the ascending and descending aorta area measurements by three-dimensional (3D) ultrasound using spatiotemporal image correlation (STIC) in the rendering mode comparing these measurements with pregestational diabetic mothers and assessing the reproducibility of the method.

Methods

We carried out a retrospective cross-sectional study with 58 normal and nine fetuses from pregestational diabetic mothers between 20 and 33 + 6 weeks of gestation. Fetal heart volumes were acquired at the level of four-chamber view to obtain the reconstructed planes for the ascending and descending aorta areas in the rendering mode. Linear regression was performed to assess the correlation between the fetal aorta areas and gestational age (GA). To assess the intra- and interobserver reproducibility, we used the concordance correlation coefficient (CCC).

Results

The mean ascending and descending aorta areas were 0.12 (0.02-0.48) and 0.11 (0.04-0.39) cm2 in normal fetuses, respectively. There was a moderate positive correlation between GA and ascending aorta area measurements (0.005676*GA - 0.01283; r = 0.53, P < 0.0001) and strong positive correlation between GA and descending aorta area (0.01095*GA - 0.1581; r = 0.68, P < 0.0001). We observed a weak intra- and interobserver reproducibility with CCC ranging from 0.05 to 0.91. The mean difference in the ascending and descending aorta area measurements of normal and fetuses of pregestational diabetic mothers was -0.03 cm2 (P = 0.276) and -0.03 cm2 (P = 0.231), respectively.

Conclusion

The fetal ascending and descending aorta area measurements obtained by 3D ultrasound using STIC in the rendering mode increased with GA in normal fetuses. The method showed weak intra- and interobserver reproducibility.

Fetal intelligent navigation echocardiography (FINE) has superior performance compared to manual navigation of the fetal heart by non-expert sonologists

OBJECTIVES

Manual and intelligent navigation (i.e. fetal intelligent navigation echocardiography or FINE) by the operator are two methods to obtain standard fetal cardiac views from spatiotemporal image correlation (STIC) volumes. The objective was to compare the performance between manual and intelligent navigation (FINE) of the fetal heart by non-expert sonologists.

METHODS

In this prospective observational study, ten sonologists underwent formal training on both navigational methods. Subsequently, they were tested on their ability to obtain nine cardiac views from five STIC volumes of normal fetal hearts (19-28 gestational weeks) using such methods. The following parameters were determined for both methods: (1) success rate of obtaining nine cardiac views; (2) mean time to obtain nine cardiac views per sonologist; and (3) maximum number of cardiac views successfully obtained for each STIC volume.

RESULTS

All fetal cardiac images obtained from 100 STIC volumes (50 for each navigational method) were reviewed by an expert in fetal echocardiography. Compared to manual navigation, FINE was associated with a significantly: (1) higher success rate of obtaining eight (excluding the abdomen view) appropriate cardiac views (92-100% vs. 56-88%; all p<0.05); (2) shorter mean time (minute:seconds) to obtain nine cardiac views (2:11 ± 0:37 vs. 15:49 ± 7:44; p<0.0001); and (3) higher success rate of obtaining all nine cardiac views for a given STIC volume (86 vs. 14%; p<0.001).

CONCLUSIONS

When performed by non-expert sonologists, intelligent navigation (FINE) had a superior performance compared to manual navigation of the normal fetal heart. Specifically, FINE obtained appropriate fetal cardiac views in 92-100% of cases.

New and advanced features of fetal intelligent navigation echocardiography (FINE) or 5D heart

Congenital heart disease (CHD) is the leading organ-specific birth defect, as well as the leading cause of infant morbidity and mortality from congenital malformations. Therefore, a comprehensive screening examination of the fetal heart should be performed in all women to maximize the detection of CHD. Four-dimensional sonography with spatiotemporal image correlation (STIC) technology displays a cine loop of a complete single cardiac cycle in motion. A novel method known as Fetal Intelligent Navigation Echocardiography (or FINE) was previously developed to interrogate STIC volume datasets using "intelligent navigation" technology. Such method allows the automatic display of nine standard fetal echocardiography views required to diagnose most cardiac defects. FINE considerably simplifies fetal cardiac examinations and reduces operator dependency. It has both high sensitivity and specificity for the detection of CHD. Indeed, FINE has been integrated into several commercially available ultrasound platforms.Recently, eight novel and advanced features have been developed for the FINE method and they will be described herein. Such features can be categorized based upon their broad goals. The first goal is to simplify FINE further, and consists of the following features: (1) Auto fetal positioning (or FINE align); (2) Skip points; (3) Predictive cursor; (4) Static mode volume; and (5) Breech sweep. The second goal is to allow quantitative measurements to be performed on the cardiac views generated by FINE: (6) Automatic cardiac axis; and (7) Cardiac biometry. Finally, the last goal is to improve the success of obtaining fetal echocardiography view(s); and consists of (8) Maestro planar navigation.

4D imaging of fetal right ventricle-feasibility study and a review of the literature

Functional analysis of the fetal cardiovascular system is crucial for the assessment of fetal condition. Evaluation of the right ventricle with standard 2D echocardiography is challenging due to its complex geometry and irregular muscle fibers arrangement. Software package TOMTEC 4D RV-Function is an analysis tool which allows assessment of right ventricular function based on volumetric measurements and myocardial deformation. The aim of this study was to determine the feasibility of this method in fetal echocardiography. The retrospective study was conducted in the high-flow Referral Center for Fetal Cardiology. We recorded 4D echocardiographic sequences of 46 fetuses with normal hearts. Following parameters were calculated: end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV) and ejection fraction (EF), right ventricle longitudinal free-wall (RVLS free-wall) and septal strain (RVLS septum). Tei index was calculated as a standard measure or RV function for comparison. 4D assessment was feasible in 38 out of 46 fetuses (83%). RV volumetric parameters—EDV, ESV and SV—increased exponentially with gestational age. Functional parameters—RV Tei index, EF and strains—were independent of gestational age. Mean EF was 45.2% (± 6%), RV free-wall strain was − 21.2% and RV septal strain was − 21.5%. There was a statistically significant correlation between septal and free-wall strains (r = 0.51, p = 0.001) as well as between EF and RV free-wall strain (r = − 0.41, p = 0.011). 4D RV assessment is feasible in most fetuses. Its clinical application should be further investigated in larger prospective studies.

3D/4D spatiotemporal image correlation (STIC) fetal echocardiography provides incremental benefit over 2D fetal echocardiography in predicting postnatal surgical approach in double-outlet right ventricle

OBJECTIVE

To analyze the incremental benefit of 3D/4D spatiotemporal image correlation (STIC) fetal echocardiography over 2D fetal echocardiography with respect to the accuracy of identification of anatomic details crucial for surgical decision-making and in predicting surgical approach in fetuses with double-outlet right ventricle (DORV).

METHODS

This was a retrospective study of fetuses with DORV which had undergone both 2D echocardiography and 3D/4D STIC echocardiography and which underwent surgery postnatally in a tertiary pediatric cardiac center in Kerala between October 2015 and March 2019. All such cases with normal atrial arrangement, concordant atrioventricular connections and balanced ventricles were included. 2D and 3D/4D STIC fetal echocardiographic data were analyzed by two experienced observers blinded to the other dataset. Anatomic variables crucial for surgical decision-making, i.e. location and routability of the ventricular septal defect, relationship of the great arteries and presence of outflow obstruction, were compared between the two modalities with respect to agreement with postnatal echocardiography. The accuracy of prenatal prediction of the surgical pathway was compared between 2D and 3D/4D modalities with respect to the procedure undertaken.

RESULTS

Included in the study were 22 fetuses with DORV which had undergone both 2D and 3D/4D imaging as well as postnatal surgery. Accuracy of prenatal interpretation of all four anatomic variables was significantly higher using 3D/4D STIC than using 2D fetal echocardiography (19/22 (86.4%) vs 8/22 (36.4%), P < 0.001). Surgical procedures included single-stage repair in 14 (63.5%) patients and a multistage approach in eight (36.4%). Prenatal prediction of the surgical pathway was significantly more accurate on 3D/4D STIC than on 2D echocardiography (20/22 (90.9%) vs 12/22 (54.5%), P = 0.021). Prenatal predictive accuracy of single-stage biventricular repair was significantly better for 3D/4D STIC than for 2D echocardiography (14/14 (100%) vs 8/14 (57.1%), P = 0.04).

CONCLUSION

Addition of 3D/4D STIC to conventional 2D fetal echocardiography confers incremental benefit on the accuracy of identification of anatomic details crucial for surgical decision-making and the prediction of postnatal surgical approach in fetuses with DORV, thereby potentially aiding prenatal counseling. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Z-Score Reference Ranges for the Offset of the Tricuspid Septal Leaflet in Normal Fetuses

OBJECTIVES

To determine Z-score equations and reference ranges for mitral valve-tricuspid valve distance (MTD) and the MTD index in the fetal heart.

METHODS

A prospective cross-sectional study was performed in 899 normal singleton fetuses from 14 to 40 weeks' gestation. The MTD and interventricular septum length (IVSL) were measured offline after electronic cardiac spatiotemporal image correlation volume acquisition. The MTD index was determined as the ratio of MTD to IVSL. Z-score reference ranges of these measurements were determined against gestational age (GA) and estimated fetal weight (EFW), using regression analysis of the mean and standard deviation (SD).

RESULTS

Strong positive correlations were found between the MTD and the independent variables. A simple linear regression model was the best description of the mean and SD of MTD based on GA, while a cubic regression best fitted the mean MTD against EFW. In contrast, the MTD index decreased progressively with the independent variables. Fractional polynomials best fitted the MTD index in terms of GA and EFW.

CONCLUSION

Normal reference values and Z-scores of fetal MTD and MTD index were provided against GA and EFW, which may be useful tools for quantitative assessment of some cardiac and extracardiac diseases.

Electronic spatiotemporal image correlation improves four-dimensional fetal echocardiography

OBJECTIVES

To compare the efficiency of electronic spatiotemporal image correlation (eSTIC) with that of conventional STIC to acquire four-dimensional (4D) fetal cardiac volumes of diagnostic quality.

METHODS

This was a randomized controlled trial of 100 patients in mid-gestation with normal sonograms. In half of the cases, STIC volumes of the fetal heart were obtained with a conventional mechanical 4D probe and in the remaining cases eSTIC volumes were obtained with an electronic 4D probe. Examinations were kept within the timeframe allotted for a standard examination of fetal anatomy, and a maximum of two attempts were made at obtaining a 4D cardiac volume. Datasets were stored on a computer and subsequently analyzed and categorized as being of optimal, satisfactory or inadequate quality, depending on whether or not it was possible to perform an extended basic cardiac examination, including obtaining a three vessels and trachea view, as well as a clear reconstruction of both the aortic and ductal arches in the sagittal plane.

RESULTS

The eSTIC volume datasets were more frequently of optimal or satisfactory diagnostic quality compared with conventional STIC (94% vs 76%, P < 0.0001). Failure to obtain an eSTIC volume of adequate quality was in all cases the consequence of an unfavorable position of the fetus.

CONCLUSIONS

Compared with a standard mechanical probe, the electronic 4D probe facilitates acquisition of sonographic cardiac volumes in mid-trimester fetuses. In our hands, eSTIC volumes of optimal or satisfactory diagnostic quality, allowing a detailed offline evaluation of the fetal heart, were obtained in more than 90% of cases within the time frame of a standard examination of fetal anatomy. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Feasibility assessment for successfully visualizing the fetal heart utilizing spatiotemporal image correlation

PURPOSE

Spatiotemporal image correlation (STIC) is an excellent imaging modality for observing the fetal heart. High-quality STIC volume data are needed for an antenatal anatomic survey to diagnose congenital heart disease. We aimed to clarify the causes of unsuccessful STIC volume data acquisition and describe a more accurate, efficient STIC examination.

METHODS

This cross-sectional study of 1124 women with fetuses assessed risk factors for unsuccessful acquisition of STIC volume data. Logistic regression analysis quantified the relation between unsuccessful acquisition and clinical variables, including maternal body mass index (BMI), shadowing artifacts due to unexpected fetal limb movement (SAU), estimated fetal weight (EFW), gestational age (GA), use of volume rendering images in four-dimensional ultrasonography (4D-US), fetal heart rate (FHR), maternal age, anterior placenta, and prior lower abdominal surgery.

RESULTS

STIC volume data acquisition was unsuccessful in 210 of 1124 (18.6%) cases. SAU, BMI ≥ 28 kg/m², not using volume rendering images in 4D-US, EFW ≥ 1300 g, and anterior placenta were independent risk factors for unsuccessful STIC data acquisition.

CONCLUSIONS

Avoiding SAU was the most important factor for accurate, efficient STIC evaluations for diagnosing congenital heart disease antenatally. The risk was not explained by lack of sonographer proficiency. Volume rendering images in 4D-US is a promising approach to successful acquisition of STIC volume data.

Prenatal screening of fetal ventriculoarterial connections: benefits of 4D technique in fetal heart imaging

Background

Identification of prenatal ventriculoarterial connections in fetuses with conotruncal anomalies (CTA) remains one of the greatest challenges for sonographers performing screening examinations. Herein, we propose a novel protocol of 4D volume analysis that identifies ventriculoarterial connections and evaluate its clinical utility in routine screenings.

Methods

Twenty-nine cases of transposition of the great arteries (TGA), 22 cases of double-outlet right ventricle (DORV), 36 cases of tetralogy of Fallot (TOF), 14 cases of truncus arteriosus (TCA), and randomly selected 70 normal fetuses were reviewed in this study. All cases were evaluated using 2D data alone (2D method), post-processing volumes with no exact algorithm (4D-1 method), or with the proposed algorithm (4D-2 method), or using the 2D and 4D data together (combined method). Comparisons were made to evaluate the detection rate of ventriculoarterial connections for these different methods.

Results

During 18–28 gestational weeks, the detection rate of 4D-2 modality was satisfactory. The detection rate of the combined method was significantly higher than 2D method in the identification of TGA, TOF, and TCA. The detection rate of 4D-1 method was significantly lower than 4D −2 modality for CTA fetuses. During late pregnancy, the detection rate for both 4D modalities was very low due to the poor quality of the 4D volumes.

Conclusions

We proposed a detailed protocol, which allowed the examiner to identify fetal ventriculoarterial connections by 4D volumes. Inclusion of blood information into the volumes improved diagnosis. Our findings suggest that the incorporation of 4D STIC into routine screenings could improve the detection for TGA, TOF, and TCA.

Electronic supplementary material

The online version of this article (doi:10.1186/s12947-017-0108-5) contains supplementary material, which is available to authorized users.

Consistent reconstruction of 4D fetal heart ultrasound images to cope with fetal motion

PURPOSE

4D ultrasound imaging of the fetal heart relies on reconstructions from B-mode images. In the presence of fetal motion, current approaches suffer from artifacts, which are unrecoverable for single sweeps.

METHODS

We propose to use many sweeps and exploit the resulting redundancy to automatically recover from motion by reconstructing a 4D image which is consistent in phase, space, and time. An interactive visualization framework to view animated ultrasound slices from 4D reconstructions on arbitrary planes was developed using a magnetically tracked mock probe.

RESULTS

We first quantified the performance of 10 4D reconstruction formulations on simulated data. Reconstructions of 14 in vivo sequences by a baseline, the current state-of-the-art, and the proposed approach were then visually ranked with respect to temporal quality on orthogonal views. Rankings from 5 observers showed that the proposed 4D reconstruction approach significantly improves temporal image quality in comparison with the baseline. The 4D reconstructions of the baseline and the proposed methods were then inspected interactively for accessibility to clinically important views and rated for their clinical usefulness by an ultrasound specialist in obstetrics and gynecology. The reconstructions by the proposed method were rated as 'very useful' in 71% and were statistically significantly more useful than the baseline reconstructions.

CONCLUSIONS

Multi-sweep fetal heart ultrasound acquisitions in combination with consistent 4D image reconstruction improves quality as well as clinical usefulness of the resulting 4D images in the presence of fetal motion.

Three- and four-dimensional ultrasound in fetal echocardiography: an up-to-date overview

Congenital heart diseases (CHD) are the most commonly overlooked lesions in prenatal screening programs. Real-time two-dimensional ultrasound (2DUS) is the conventionally used tool for fetal echocardiography. Although continuous improvements in the hardware and post-processing software have resulted in a good image quality even in late first trimester, 2DUS still has its limitations. Four-dimensional ultrasound with spatiotemporal image correlation (STIC) is an automated volume acquisition, recording a single three-dimensional (3D) volume throughout a complete cardiac cycle, which results in a four-dimensional (4D) volume. STIC has the potential to increase the detection rate of CHD. The aim of this study is to provide a practical overview of the possibilities and (dis)advantages of STIC. A review of literature and evaluation of the current status and clinical value of 3D/4D ultrasound in prenatal screening and diagnosis of congenital heart disease are presented.

Feasibility Study on Prenatal Cardiac Screening Using Four-Dimensional Ultrasound with Spatiotemporal Image Correlation: A Multicenter Study

Objective

This study aimed at investigating the feasibility of using the spatiotemporal image correlation (STIC) technology for prenatal cardiac screening, finding factors that influence the offline evaluation of reconstructed fetal heart, and establishing an optimal acquisition scheme.

Methods

The study included 452 gravidae presenting for routine screening at 3 maternity centers at 20–38 gestational weeks. The factors influencing the quality of STIC volume data were evaluated using t test, chi-square test, and logistic regression analysis. The predictive power was evaluated using the receiver operating characteristic (ROC) curve.

Results

Among the 452 fetuses enrolled, 353 (78.1%) were identified as successful and 99 (21.9%) as failure of evaluation of the reconstructed fetal heart. The total success rate of qualified STIC images was 78.1%. The display rates of reconstructed cardiac views were 86.5% (four-chamber view), 92.5% (left ventricular outflow tract view), 92.7% (right ventricular outflow tract view), 89.9% (three-vessel trachea view), 63.9% (aortic arch view), 81.4% (ductal arch view), 81% (short-axis view of great vessels), 80.1% (long-cava view), and 86.9% (abdominal view). A logistic regression analysis showed that more than 28 gestational weeks [OR = 0.39 (CI 95% 0.16, 0.19), P = 0.035], frequent fetal movements [OR = 0.37 (CI 95% 0.16, 0.87), P = 0.022], shadowing [OR = 0.36 (CI 95% 0.19, 0.72), P = 0.004], spine location at 10–2 o’clock [OR = 0.08 (CI 95% 0.02, 0.27), P = 0.0], and original cardiac view [OR = 0.51 (0.25, 0.89), P = 0.019] had a significant impact on the quality of STIC. The area under the ROC curve was 0.775.

Conclusions

Fetal cardiac-STIC seems a feasible tool for prenatal screening of congenital heart diseases. The influence factors on the quality of STIC images included the intensity of training, gestational age, fetal conditions and parameter settings. The optimal acquisition scheme may improve the application and widespread use of cardiac STIC.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 2

The effective performance of fetal cardiac examination using spatiotemporal image correlation (STIC) technology requires 2 essential steps: volume acquisition and postprocessing. An important prerequisite is training sonologists to acquire high-quality volume data sets so that when analyzed, such volumes are informative. This article is part 2 of a series on 4-dimensional sonography with STIC. Part 1 focused on STIC technology and its features, the importance of operator training/experience and acquisition of high-quality STIC volumes, factors that affect STIC volume acquisition rates, and general recommendations on performing 4D sonography with STIC. In part 2, we discuss a detailed and practical stepwise approach for STIC volume acquisition, along with methods to determine whether such volumes are appropriate for analysis.

How to Acquire Cardiac Volumes for Sonographic Examination of the Fetal Heart: Part 1

Four-dimensional sonography with spatiotemporal image correlation (STIC) technology allows acquisition of a fetal cardiac volume data set and displays a cine loop of a complete single cardiac cycle in motion. Part 1 of this 2-part article reviews STIC technology and its features, the importance of operator training/experience, and acquisition of high-quality STIC volumes, as well as factors that affect STIC volume acquisition rates. We also propose a detailed and practical stepwise approach to performing 4-dimensional sonography with STIC and begin herein by providing general recommendations. Part 2 will discuss specifics of the approach, along with how to determine whether such volumes are appropriate for analysis.

Prospective evaluation of the fetal heart using Fetal Intelligent Navigation Echocardiography (FINE)

OBJECTIVE

To evaluate prospectively the performance of Fetal Intelligent Navigation Echocardiography (FINE) applied to spatiotemporal image correlation (STIC) volume datasets of the normal fetal heart.

METHODS

In all women between 19 and 30 weeks' gestation with a normal fetal heart, an attempt was made to acquire STIC volume datasets of the apical four-chamber view if the following criteria were met: (1) fetal spine located between 5- and 7-o'clock positions; (2) minimal or absent shadowing (including a clearly visible transverse aortic arch); (3) absence of fetal breathing, hiccups, or movement; and (4) adequate image quality. Each STIC volume successfully acquired was evaluated by STICLoop™ to determine its appropriateness before applying the FINE method. Visualization rates of fetal echocardiography views using diagnostic planes and/or Virtual Intelligent Sonographer Assistance (VIS-Assistance®) were calculated.

RESULTS

One or more STIC volumes (365 in total) were obtained successfully in 72.5% (150/207) of women undergoing ultrasound examination. Of the 365 volumes evaluated by STICLoop, 351 (96.2%) were considered to be appropriate. From the 351 STIC volumes, only one STIC volume per patient (n = 150) was analyzed using the FINE method, and consequently nine fetal echocardiography views were generated in 76-100% of cases using diagnostic planes only, in 98-100% of cases using VIS-Assistance only, and in 98-100% of cases when using a combination of diagnostic planes and/or VIS-Assistance.

CONCLUSIONS

In women between 19 and 30 weeks' gestation with a normal fetal heart undergoing prospective sonographic examination, STIC volumes can be obtained successfully in 72.5% of cases. The FINE method can be applied to generate nine standard fetal echocardiography views in 98-100% of these cases using a combination of diagnostic planes and/or VIS-Assistance. This suggests that FINE could be implemented in fetal cardiac screening programs. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Prenatal Visualization of the Pulmonary and Aortic Valves and Leaflets Is Feasible Using 4-Dimensional Sonography

OBJECTIVES

The purpose of this study was to determine whether the morphologic characteristics and area of the semilunar valves in healthy fetuses and fetuses with cardiac defects can be visualized by using spatiotemporal image correlation (STIC).

METHODS

Spatiotemporal image correlation volumes from 74 healthy fetuses were recorded in 5 examinations between the 15th and 36th weeks of pregnancy. Second, we recorded STIC volumes from 64 fetuses with various cardiac defects. The quality of the volumes was rated. The areas of the aortic and pulmonary valves were measured in systole by rendering the valves on 4-dimensional sonography. The number of leaflets was examined. Longitudinal data analysis using linear mixed models was performed.

RESULTS

Two hundred ninety-three volumes from normal hearts were examined. In 82.5%, the quality of the normal volumes was sufficient. Visualization of the valve opening was feasible in 96.1% of the normal hearts and 97.4% of the abnormal hearts. The success rate of visualization of the pulmonary and aortic valve leaflets was dependent on the gestational age, with the highest percentage (72.1% in normal hearts) at 19 to 24 weeks. Longitudinal regression analysis showed a positive relationship of the aortic and pulmonary valve areas with gestational age (P < .0001) and fetal biometric measurements (P < .0001). Fifty-eight abnormal volumes were examined. Cardiac defects with abnormal valve areas due to aortic and pulmonary stenosis could be clearly visualized by using STIC.

CONCLUSIONS

Examination of the morphologic characteristics of the semilunar valves using STIC is feasible, which is difficult when using 2-dimensional sonography. With increasing implementation of 4-dimensional sonography, the understanding of rendered images might be useful for anyone practicing fetal echocardiography.

Three-dimensional ultrasound of the fetus: how does it help?

Three-dimensional ultrasonography (3-D US) was introduced to the field of fetal imaging in the early 1990s. Since then several publications have described potential applications for the diagnosis of congenital malformations as well as organ volumetry. This article reviews basic principles of 3-D US as well as its clinical applicability to prenatal diagnosis of abnormalities involving the face, spine and skeletal system, as well as potential applications of 3-D US for fetal cardiovascular and neuroimaging. Limitations related to motion artifacts, acoustic shadowing and barriers to clinical implementation of 3-D US in clinical practice are addressed.

Evaluating Spatiotemporal Image Correlation Technology as a Tool for Training Nonexpert Sonographers to Perform Examinations of the Fetal Heart

OBJECTIVES

We aimed to evaluate the use of spatiotemporal image correlation (STIC) as a tool for training nonexpert examiners to perform screening examinations of the fetal heart by acquiring and examining STIC volumes according to a standardized questionnaire based on the 5 transverse planes of the fetal heart.

METHODS

We conducted a prospective study at 2 tertiary care centers. Two sonographers without formal training in fetal echocardiography received theoretical instruction on the 5 fetal echocardiographic transverse planes, as well as STIC technology. Only women with conditions allowing 4-dimensional STIC volume acquisitions (grayscale and Doppler) were included in the study. Acquired volumes were evaluated offline according to a standardized protocol that required the trainee to mark 30 specified structures on 5 required axial planes. Volumes were then reviewed by an expert examiner for quality of acquisition and correct identification of specified structures.

RESULTS

Ninety-six of 112 pregnant women examined entered the study. Patients had singleton pregnancies between 20 and 32 weeks' gestation. After an initial learning curve of 20 examinations, trainees succeeded in identifying 97% to 98% of structures, with a highly significant degree of agreement with the expert's analysis (P < .001). A median of 2 STIC volumes for each examination was necessary for maximal structure identification. Acquisition quality scores were high (8.6-8.7 of a maximal score of 10) and were found to correlate with identification rates (P = .017).

CONCLUSIONS

After an initial learning curve and under expert guidance, STIC is an excellent tool for trainees to master extended screening examinations of the fetal heart.

Prenatal examination of the area and morphology of the atrioventricular valves using four-dimensional ultrasound in normal and abnormal hearts

OBJECTIVE

Our aim is to evaluate the feasibility to examine the morphology and area of the atrioventricular (AV) valves in normal fetuses and fetuses with cardiac defects using spatiotemporal image correlation (STIC).

METHODS

Atrioventricular valves were analyzed longitudinally in STIC volumes of 74 normal fetuses between the 15th and 36th week of pregnancy. The valve area was measured in a rendered view in diastole, the number of valve leaflets in systole. Longitudinal data analysis was performed using linear mixed models. Fifty fetuses with cardiac defects were examined.

RESULTS

Examination of 355 STIC volumes of normal fetuses showed in 82.5% sufficient quality. The tricuspid valve leaflets were seen in 200 (68.3%) volumes and the mitral valve leaflets in 219 (74.7%) volumes. The tricuspid valve showed in 61.1% a round, 29.0% rectangle, and 8.9% elliptical shape and the mitral valve in 60.1% round, 28.0% rectangle, and 10.9% elliptical. Regression analysis revealed a positive relationship of the valve area with gestational age (p < 0.0001). Most heart defects with stenosis showed an area below the 5th percentile.

CONCLUSION

Prenatal examination of the morphology and area of the AV valves using four-dimensional ultrasound is feasible. A rectangular valve opening is normal, which was visualized in about one third of the normal fetuses.

Differential and linear insertion of atrioventricular valves: a useful tool?

OBJECTIVE

The differential insertion of the atrioventricular valves is the ultrasonographic representation of the more apical attachment of the tricuspid valve to the septum with respect to the mitral valve. A linear insertion is present when both valves form a linear continuum and has been suggested as a marker for atrioventricular septal defects (AVSDs). The objective of this study was to evaluate the anatomical substratum of differential and linear insertions of the atrioventricular valves in normal fetal hearts and fetal hearts with an AVSD.

METHODS

The extent and position of the fibrous skeleton and attachment of the atrioventricular valves to the septum were studied in histological sections of 17 normal hearts and four hearts with an AVSD from 10 + 0 weeks' gestation to 3 days postpartum with various immunohistochemical tissue markers. In addition, spatiotemporal image correlation (STIC) volumes of 10 normal hearts and STIC volumes of eight hearts with an AVSD at 13 + 6 to 35 + 5 weeks' gestation were examined.

RESULTS

The differential insertion of the atrioventricular valves was visible in normal hearts in the four-chamber plane immediately beneath the aorta, but nearer the diaphragm a linear insertion was found. In hearts with an AVSD, a linear appearance was observed in the four-chamber plane immediately beneath the aorta. Towards the diaphragm, however, first a differential insertion and, more caudally, a linear insertion was found.

CONCLUSIONS

Both differential and linear insertions can be found in normal fetal hearts and fetal hearts with AVSD, depending on the plane in which the four-chamber view is visualized. Therefore, measurement of the differential insertion is likely to be useful only in experienced hands.

Assessment of Quality of Fetal Heart Views by 3D/4D Ultrasonography Using Spatio-Temporal Image Correlation in the Second and Third Trimesters of Pregnancy

OBJECTIVE

To assess the quality of fetal heart views by three-dimensional/four-dimensional (3D/4D) ultrasonography using spatio-temporal image correlation (STIC) in the second and third trimester of pregnancy.

METHODS

This prospective and cross-sectional study was conducted at a single referral service for the screening of congenital heart diseases (CHDs), with pregnant women at 20-30 weeks' gestation with a normal fetal heart. 3D/4D STIC were obtained from the fetal heart screening in the following views: four-chamber (4C), left and right ventricular outflow tracts (LVOT and RVOT), 3 vessels and trachea (3VT), aortic arch (AA), and ductal arch (DA). We categorized the images as satisfactory or unsatisfactory and performed McNemar's test to evaluate the differences between the two-dimensional (2D) echocardiography and 3D/4D STIC techniques. The inter-observer concordance was obtained by kappa coefficient.

RESULTS

The rate of satisfactory fetal heart views using 3D/4D STIC was 54% by using 4 planes (4C, RVOT, LVOT, and 3VT) and 14% by using 6 planes (4C, RVOT, LVOT, 3VT, AA, and DA). In contrast, 100% of the 2D echocardiography images were satisfactory (McNemar's test, P < 0.001). We observed moderate inter-observer concordance to both 4- and 6 planes (κ = 0.56 and 0.43, respectively).

CONCLUSION

The quality of the main fetal heart views by 3D/4D STIC still present some limitations compared with the 2D echocardiography.

Differential insertion of the atrioventricular valves: measurement protocol to detect various congenital heart defects

OBJECTIVES

The objectives of this study were to develop reference values for the distance between the atrioventricular valves, called differential insertion of the atrioventricular valves (DIAVV), in normal fetuses using four-dimensional ultrasound with spatio-temporal image correlation and to explore if DIAVV measurement can differentiate between normal hearts and hearts with cardiac defects.

METHODS

The DIAVV was analysed longitudinally following a measurement protocol in 74 fetuses between 15 and 36 weeks gestational age. The DIAVV was measured in an apical four-chamber view of the heart in end-diastole. Furthermore, the DIAVV was measured in 70 fetuses with cardiac defects.

RESULTS

In total, 337 normal and 70 abnormal spatio-temporal image correlation volumes were examined. Longitudinal regression analysis revealed a positive relationship of the DIAVV with gestational age and fetal biometry (p < 0.0001). The DIAVV of fetuses with double outlet right ventricle, truncus arteriosus, atrioventricular septal defects, Ebstein and tetralogy of Fallot all differed from normal fetuses (p < 0.05).

CONCLUSION

Measurement of the DIAVV is a promising tool; however, a well-defined measurement protocol should be followed to accomplish the correct plane and exact moment in the cardiac cycle. This study presents new nomograms following this measurement protocol and reports an abnormal DIAVV in a wide spectrum of congenital heart disease.

Real-time three-dimensional foetal echocardiography using a new transabdominal xMATRIX array transducer

BACKGROUND

Foetal echocardiography has been used to diagnose congenital heart disease. However, conventional echocardiography can only display two-dimensional (2D) structural images of the intricate three-dimensional (3D) foetal heart.

AIM

The purpose of this study was to report the first use of a new transabdominal xMATRIX array transducer and to describe its ability to perform all 3D modalities: intelligent spatiotemporal image correlation (iSTIC) acquisition, xPlane imaging and 3D surface imaging.

METHODS

Eighty foetuses without congenital heart disease were included consecutively, with a gestational age between 20 and 37 weeks. 2D and 3D scans were performed with a transabdominal xMATRIX array transducer. Cardiac-STIC volume datasets were acquired and postprocessed with new automatic software (the 'Fetal Heart Navigator').

RESULTS

A total of 224 iSTIC acquisitions were performed (mean time for each, 2 seconds). Only 78 iSTIC acquisitions (35%) were able to detect the ductal arch automatically. 'Fetal Heart Navigator' feasibility varied according to foetal position, including the descending aorta. Live xPlane imaging had excellent feasibility regardless of foetal position; using rotation, lateral and vertical tilts, all cardiac structures were identified from a unique reference plane. Live 3D surface imaging had variable feasibility depending on the target structure. Only 10% of the volume dataset offered comprehensive imaging of intracardiac views.

CONCLUSION

The new xMATRIX transabdominal transducer allows a multimodality approach to the foetal heart. Further studies that include foetuses with cardiac malformations are required.

Comparison of fetal cardiac spatiotemporal image correlation segmental analysis between cardiac- and body-based scrolling

OBJECTIVES

The purpose of this study was to compare success rates for depiction of the 5 typical transverse planes in the fetal upper thorax between cardiac- and body-based scrolling techniques.

METHODS

Spatiotemporal image correlation volume data sets acquired at the 4-chamber view level were obtained from low-risk singleton pregnancies with healthy fetuses. Each data set was analyzed by the authors using both cardiac- and body-based techniques. With the cardiac-based technique, the exact 4-chamber view was first identified as an initial plane before scrolling, whereas with the body-based technique, a volume data set was first manipulated to get the fetal orientation in the exact dorsal supine position as an initial plane. In both techniques, the volumes were then scrolled through the upper thorax to identify the standard planes, including the 4-chamber, 5-chamber, 3-vessel, 3-vessel and trachea, and aortic arch views.

RESULTS

An analysis of 50 volume data sets to evaluate intraobserver and interobserver variability in the success rates for the 4-chamber, 5-chamber, 3-vessel, 3-vessel and trachea, and aortic arch views showed good agreement. In an analysis of 296 separate data sets, cardiac-based scrolling was associated with significantly higher success rates than body-based scrolling in all standard planes (P < .05).

CONCLUSIONS

Cardiac-based scrolling resulted in higher success rates for obtaining the standard spatiotemporal image correlation planes than body-based scrolling. Therefore, examiners in the early part of the learning curve should be encouraged to first identify a perfect 4-chamber view at the start of an examination.

The new 3D/4D based spatio-temporal imaging correlation (STIC) in fetal echocardiography: a promising tool for the future

Congenital heart disease is the commonest congenital anomaly. It is much more common than chromosomal malformations and spinal defects. Its estimated incidence is about 4-13 per 1000 live births. Congenital heart disease is a significant cause of fetal mortality and morbidity. Antenatal diagnosis of congenital heart disease is extremely difficult and requires extensive training and expertise. The detection rate of congenital heart disease is very variable and it ranged from 35 to 86% in most studies. In the light of the above, the introduction of the new 3D/4D based spatio-temporal Image Correlation (STIC) is highly welcomed to improve antenatal detection of congenital heart disease. STIC is an automated device incorporated into the ultrasound probe and has the capacity to perform slow sweep to acquire a single 3-dimensional (3D) volume. This acquired volume is composed of a great number of 2-dimension (2D) frames. This volume can be analyzed and reanalyzed as required to demonstrate all the required cardiac views. It also provides the examiner with the ability to review all images in a looped cine sequence. This technology has the ability to improve our ability to examine the fetal heart in the acquired volume and decrease examination time. Using this technique you can share the information and consult colleagues both at your clinical sitting or remotely using the internet.

Fetal Intelligent Navigation Echocardiography (FINE): a novel method for rapid, simple, and automatic examination of the fetal heart

OBJECTIVE

To describe a novel method (Fetal Intelligent Navigation Echocardiography (FINE)) for visualization of standard fetal echocardiography views from volume datasets obtained with spatiotemporal image correlation (STIC) and application of 'intelligent navigation' technology.

METHODS

We developed a method to: 1) demonstrate nine cardiac diagnostic planes; and 2) spontaneously navigate the anatomy surrounding each of the nine cardiac diagnostic planes (Virtual Intelligent Sonographer Assistance (VIS-Assistance®)). The method consists of marking seven anatomical structures of the fetal heart. The following echocardiography views are then automatically generated: 1) four chamber; 2) five chamber; 3) left ventricular outflow tract; 4) short-axis view of great vessels/right ventricular outflow tract; 5) three vessels and trachea; 6) abdomen/stomach; 7) ductal arch; 8) aortic arch; and 9) superior and inferior vena cava. The FINE method was tested in a separate set of 50 STIC volumes of normal hearts (18.6-37.2 weeks of gestation), and visualization rates for fetal echocardiography views using diagnostic planes and/or VIS-Assistance® were calculated. To examine the feasibility of identifying abnormal cardiac anatomy, we tested the method in four cases with proven congenital heart defects (coarctation of aorta, tetralogy of Fallot, transposition of great vessels and pulmonary atresia with intact ventricular septum).

RESULTS

In normal cases, the FINE method was able to generate nine fetal echocardiography views using: 1) diagnostic planes in 78-100% of cases; 2) VIS-Assistance® in 98-100% of cases; and 3) a combination of diagnostic planes and/or VIS-Assistance® in 98-100% of cases. In all four abnormal cases, the FINE method demonstrated evidence of abnormal fetal cardiac anatomy.

CONCLUSIONS

The FINE method can be used to visualize nine standard fetal echocardiography views in normal hearts by applying 'intelligent navigation' technology to STIC volume datasets. This method can simplify examination of the fetal heart and reduce operator dependency. The observation of abnormal echocardiography views in the diagnostic planes and/or VIS-Assistance® should raise the index of suspicion for congenital heart disease.

Performance of different scan protocols of fetal echocardiography in the diagnosis of fetal congenital heart disease: a systematic review and meta-analysis

OBJECTIVE

The rapid progress in fetal echocardiography has lead to early detection of congenital heart diseases. Increasing evidences have shown that prenatal diagnosis could be life saving in certain cases. However, there is no agreement on which protocol is most adaptive diagnostic one. Thus, we use meta-analysis to conduct a pooled performance test on 5 diagnostic protocols.

METHODS

We searched PUBMED, EMBASE, the Cochrane Central Register of Controlled Trials and WHO clinical trails registry center to identify relevant studies up to August, 2012. We performed meta-analysis in a fixed/random-effect model using Meta-disc 1.4. We used STATA 11.0 to estimate the publication bias and SPSS 17.0 to evaluate variance.

RESULTS

We use results from 81 studies in 63 articles to analyze the pooled accuracy. The overall performance of pooled sensitivities of spatiotemporal image correlation (STIC), extend cardiac echography examination (ECEE) and 4 chambers view + outflow tract view + 3 vessels and trachea view (4 CV+OTV+3 VTV) were around 0.90, which was significant higher than that of 4 chambers view + outflow tract view or 3 vessels and trachea view (4 CV+OTV/3 VTV) and 4 chambers view (4 CV). Unfortunately the pooled specificity of STIC was 0.92, which was significant lower than that of other 4 protocols which reached at 1.00. The area under the summary receiver operating characteristic curves value of STIC, ECEE, 4 CV+OTV+3 VTV, 4 CV+OTV/3 VTV and 4 CV were 0.9700, 0.9971, 0.9983, 0.9929 and 0.9928 respectively.

CONCLUSION

These results suggest a great diagnostic potential for fetal echocardiography detection as a reliable method of fetal congenital heart disease. But at least 3 sections view (4 CV, OTV and 3 VTV) should be included in scan protocol, while the STIC can be used to provide more information for local details of defects, and can not be used to make a definite diagnosis alone with its low specificity.

Application of spatio-temporal image correlation technology in the diagnosis of fetal cardiac abnormalities

Congenital heart disease is the birth defect with the highest incidence in China. Its timely and accurate prenatal diagnosis is critical for appropriate perinatal and postnatal management and salvage treatment. With improvements in the diagnostic capabilities of ultrasound and clinical manipulation techniques, prenatal diagnosis is conducted increasingly early and with greater accuracy. However, the representations of tiny blood vessels and the determination of abnormal spatial structures in the fetal period continue to cause difficulties in prenatal diagnosis. In theory, spatio-temporal image correlation (STIC) technology is able to compensate for the defects of previous traditional two-dimensional (2D) ultrasound and improve the diagnostic accuracy. The aim of the present study was to investigate the clinical application value of STIC technology combined with traditional 2D ultrasound in the diagnosis of fetal cardiac abnormalities. A total of 1,286 fetuses were subjected to sequential echocardiographic examination, during which STIC technology was used to collect heart volume data and carry out image post-processing and off-line analysis. In addition, the prenatal and postnatal echocardiography results were compared with the pathology results following the induced labor of fetuses with cardiac abnormalities. The sensitivity, specificity, misdiagnosis rate and rate of missed diagnosis for the STIC technology in the diagnosis of prenatal fetal cardiac abnormalities were 97.4, 99.6, 0.4 and 2.6%, respectively. The total coincidence rate was 99.2% and the positive and negative predictive values were 97.9 and 99.4%, respectively; the statistics for the consistency check of the STIC technology in the diagnosis of fetal cardiac abnormalities are κ=0.991, P=0.000. STIC technology combined with fetal echocardiography may be used for the definite diagnosis of fetal heart malformations, with high sensitivity and specificity.

Detection of the fetal conotruncal anomalies using real-time three-dimensional echocardiography with live xPlane imaging of the fetal ductal arch view

OBJECTIVE

To evaluate the role of live xPlane imaging of ductal arch view in detection of fetal conotruncal anomalies.

METHODS

Two hundred selected singleton pregnancies, including 152 normal cases, 27 conotruncal anomalies and 21 other types of fetal heart abnormalities were enrolled in this observational study. All the cases were scanned to visualize the ductal arch view with live xPlane imaging by a single observer. The detection rate of conotruncal and non-conotruncal anomalies with live xPlane imaging was compared.

RESULTS

In using this new method of live xPlane imaging, an abnormal ductal arch view was visualized in 92.6% of fetal conotruncal anomalies, compared with that of non-conotruncal anomalies (23.8%, p < 0.001).

CONCLUSION

The ductal arch view can be obtained by live xPlane imaging. This method is relatively simple and feasible, hence may be a useful tool to detect fetal conotruncal anomalies.

The fetal cardiovascular response to increased placental vascular impedance to flow determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

We sought to determine if increased placental vascular impedance to flow is associated with changes in fetal cardiac function using spatiotemporal image correlation and virtual organ computer-aided analysis.

STUDY DESIGN

A cross-sectional study was performed in fetuses with umbilical artery pulsatility index >95th percentile (abnormal [ABN]). Ventricular volume (end-systole, end-diastole), stroke volume, cardiac output (CO), adjusted CO, and ejection fraction were compared to those of 184 normal fetuses.

RESULTS

A total of 34 fetuses were evaluated at a median gestational age of 28.3 (range, 20.6-36.9) weeks. Mean ventricular volumes were lower for ABN than normal cases (end-systole, end-diastole) with a proportionally greater decrease for left ventricular volume (vs right). Mean left and right stroke volume, CO, and adjusted CO were lower for ABN (vs normal) cases. Right ventricular volume, stroke volume, CO, and adjusted CO exceeded the left in ABN fetuses. Mean ejection fraction was greater for ABN than normal cases. Median left ejection fraction was greater (vs right) in ABN fetuses.

CONCLUSION

Increased placental vascular impedance to flow is associated with changes in fetal cardiac function.

Accuracy, agreement, and reliability of fetal cardiac measurements using 4-dimensional spatiotemporal image correlation

OBJECTIVES

The purpose of this study was to evaluate the accuracy, agreement, and reliability of 4-dimensional sonography using spatiotemporal image correlation (STIC) in fetal cardiac measurements during the second and third trimesters.

METHODS

Four-dimensional cardiac STIC volumes were acquired from 150 low-risk singleton pregnancies at gestational ages of 18 to 38 weeks. A total of 11 dimensions of the fetal heart and great vessels were analyzed by two different observers. Accuracy was assessed by comparing the measurements acquired by 4-dimensional STIC with those determined by 2-dimensional echocardiography by calculating the mean error and mean percent error and depicted by Bland-Altman plots. Absolute agreement and reliability of STIC-based measurements were evaluated on the basis of an intraclass correlation coefficient (ICC).

RESULTS

For STIC-based measurements of cardiac dimensions, good accuracy was achieved by the two experienced observers (mean percent error, -3.10% to 0.87% for observer A; -2.49% to -0.33% for observer B), and absolute agreement was almost perfect (ICC, 95% confidence interval, 0.916-0.993 for observer A; 0.957-0.990 for observer B). Interobserver ICCs among the two observers were between 0.909 and 0.990 (95% confidence interval), whereas intraobserver ICCs for observer A were between 0.894 and 0.989, and those for observer B were between 0.893 and 0.985, showing no significant differences in the reliability of SITC with regard to observers.

CONCLUSIONS

Four-dimensional sonography with STIC is a feasible and accurate method for fetal cardiac dimension measurements in the second and third trimesters. It is in good agreement with 2-dimensional echocardiography and can be performed by different observers.

Can live xPlane imaging of the in-plane view of interventricular septum be used to detect fetal conotruncal anomalies?

OBJECTIVE

To evaluate the feasibility of live xPlane imaging visualizing the in-plane view of IVS in the screening of the fetal conotruncal anomalies.

METHOD

One hundred and fifty-two consecutive normal singleton fetuses and forty-eight fetal cardiac defects (27 conotruncal and 21 non-conotruncal cases), were enrolled in this study. The in-plane view of IVS was firstly acquired with live xPlane imaging and then judged whether it is normal or not by one operator. The focus was put on observing the relationship of pulmonary artery and aorta. The comparison between conotruncal and non-conotruncal anomalies in demonstrating the relationship of pulmonary artery and aorta was performed.

RESULT

There were 27 cases of conotruncal anomalies enrolled in this study and 19 cases (70.4%) had the abnormal relationship of aorta and pulmonary artery in the in-plane view of IVS. In 21 cases of non-conotruncal CHDs, however, there were only 5 cases (23.8%) had the abnormal relationship in the in-plane view of IVS (p < 0.001).

CONCLUSION

Live xPlane imaging of the in-plane view of IVS is feasible to detect the fetal conotruncal anomalies, which may potentially be a useful tool for the non-experienced operators to screen the fetal conotruncal anomalies.

Comparison of real-time three-dimensional echocardiography and spatiotemporal image correlation in assessment of fetal interventricular septum

OBJECTIVE

To compare the role of real-time 3DE and STIC technology in assessment of the fetal IVS.

METHODS

Fifty pregnant women with singleton pregnancies were invited to attend this study. All the fetuses were examined by both spatiotemporal image correlation and real-time three-dimensional echocardiography. There were totally six images of IVS obtained for each fetus: live xPlane image, live 3D image, multiplanar image and rendered image with the four-chamber view as the starting plane, multiplanar image and rendered image with the sagittal view of the fetal thorax as the starting plane. These images were grouped into six groups and randomized within each group for the further analysis. The images were scored and compared according to the image quality, the outline of the fetal IVS and motion artefact. The operator was also asked to judge whether VSD existed or not and the results were compared with the final diagnosis. The sensitivity, specificity, false positive percentage, positive likelihood ratio, false negative percentage and negative likelihood ratio of each group were also calculated.

RESULTS

There were 15 cases with VSD and four cases without VSD in CHD fetus and 31 cases of normal fetus enrolled in this study. A total 300 images of the lateral view of fetal IVS were obtained and grouped into six groups. The image quality in the group of STIC with the four-chamber view as the starting plane is much worse than the group of STIC with the sagittal view as the starting plane and real-time three-dimensional echocardiography (P < 0.05). There were no significant differences in image quality between the group of STIC with the sagittal view as the starting plane and real-time three-dimensional echocardiography (P > 0.05).

CONCLUSION

The image quality of real-time 3DE is similar to the images acquired by STIC from the sagittal view and superior to that obtained by STIC from the four-chamber view. However, real-time 3DE has no motion artefact, which has the potentials to improve the detection rate of fetal VSD.

Fetal cardiac ventricular volume, cardiac output, and ejection fraction determined with 4-dimensional ultrasound using spatiotemporal image correlation and virtual organ computer-aided analysis

OBJECTIVE

The objective of this study was to quantify fetal cardiovascular parameters using spatiotemporal image correlation (STIC) and virtual organ computer-aided analysis (VOCAL).

STUDY DESIGN

A cross-sectional study was performed in normal pregnancies (19-42 weeks) to evaluate ventricular volume, stroke volume (SV), cardiac output (CO), and ejection fraction (EF). The CO was also expressed as a function of estimated fetal weight and biometric parameters.

RESULTS

The following results were found: (1) 184 STIC datasets; (2) with advancing gestation, ventricular volume, SV, CO, and adjusted CO increased, whereas EF decreased; (3) right ventricular (RV) volume was larger than the left ventricular (LV) volume in systole (0.50 vs 0.27 mL; P < .001) and diastole (1.20 vs 1.03 mL; P < .001); (4) there were no differences between the LV and RV in SV, CO, or adjusted CO; and (5) LV EF was greater than the RV EF (72.2 vs 62.4%; P < .001).

CONCLUSION

Normal fetal cardiovascular physiology is characterized by a larger RV volume and a greater LV EF, resulting in similar LV and RV SV and CO.

Scan the fetal heart by real-time three-dimensional echocardiography with live xPlane imaging

OBJECTIVE

To describe the methodology of live xPlane imaging in the visualization of the fetal heart in detail.

METHODS

Fifty-one consecutive pregnant women with singleton pregnancies were imaged to display four screening sections of the fetal heart, the four-chamber view, the left outflow tract view (LVOT), the right outflow tract view (RVOT), and the three-vessel and trachea view (3VT), using live xPlane imaging. The methodology of how to visualize the screening planes was described in detail. We used two methods to image the fetal heart with live xPlane imaging: one uses the four-chamber view as the starting plane and the other uses the longitudinal view of fetal upper thorax as the starting plane.

RESULTS

When using the four-chamber view as the starting plane, the visualization rate of LVOT, RVOT, and 3VT was 94.1% (48/51), 100% (51/51), and 98.0% (50/51), respectively. When using the longitudinal view as the starting plane, the visualization rate of four-chamber view, LVOT, RVOT, and 3VT was 100% (51/51), 100% (51/51), 41.2% (21/51), and 100% (51/51), respectively.

CONCLUSIONS

Live xPlane imaging can be used to visualize the screening views of the fetal heart, and potentially may be a useful tool for the assessment and diagnosis of fetal congenital heart diseases.

Four-chamber view and 'swing technique' (FAST) echo: a novel and simple algorithm to visualize standard fetal echocardiographic planes

OBJECTIVE

To describe a novel and simple algorithm (four-chamber view and 'swing technique' (FAST) echo) for visualization of standard diagnostic planes of fetal echocardiography from dataset volumes obtained with spatiotemporal image correlation (STIC) and applying a new display technology (OmniView).

METHODS

We developed an algorithm to image standard fetal echocardiographic planes by drawing four dissecting lines through the longitudinal view of the ductal arch contained in a STIC volume dataset. Three of the lines are locked to provide simultaneous visualization of targeted planes, and the fourth line (unlocked) 'swings' through the ductal arch image (swing technique), providing an infinite number of cardiac planes in sequence. Each line generates the following plane(s): (a) Line 1: three-vessels and trachea view; (b) Line 2: five-chamber view and long-axis view of the aorta (obtained by rotation of the five-chamber view on the y-axis); (c) Line 3: four-chamber view; and (d) 'swing line': three-vessels and trachea view, five-chamber view and/or long-axis view of the aorta, four-chamber view and stomach. The algorithm was then tested in 50 normal hearts in fetuses at 15.3-40 weeks' gestation and visualization rates for cardiac diagnostic planes were calculated. To determine whether the algorithm could identify planes that departed from the normal images, we tested the algorithm in five cases with proven congenital heart defects.

RESULTS

In normal cases, the FAST echo algorithm (three locked lines and rotation of the five-chamber view on the y-axis) was able to generate the intended planes (longitudinal view of the ductal arch, pulmonary artery, three-vessels and trachea view, five-chamber view, long-axis view of the aorta, four-chamber view) individually in 100% of cases (except for the three-vessels and trachea view, which was seen in 98% (49/50)) and simultaneously in 98% (49/50). The swing technique was able to generate the three-vessels and trachea view, five-chamber view and/or long-axis view of the aorta, four-chamber view and stomach in 100% of normal cases. In the abnormal cases, the FAST echo algorithm demonstrated the cardiac defects and displayed views that deviated from what was expected from the examination of normal hearts. The swing technique was useful for demonstrating the specific diagnosis due to visualization of an infinite number of cardiac planes in sequence.

CONCLUSIONS

This novel and simple algorithm can be used to visualize standard fetal echocardiographic planes in normal fetal hearts. The FAST echo algorithm may simplify examination of the fetal heart and could reduce operator dependency. Using this algorithm, inability to obtain expected views or the appearance of abnormal views in the generated planes should raise the index of suspicion for congenital heart disease.

Satisfactory rate of postprocessing visualization of standard fetal cardiac views from 4-dimensional cardiac volumes acquired during routine ultrasound practice by experienced sonographers in peripheral centers

The aim of this study was to evaluate the feasibility of visualizing standard cardiac views from 4-dimensional (4D) cardiac volumes obtained at ultrasound facilities with no specific experience in fetal echocardiography. Five sonographers prospectively recorded 4D cardiac volumes starting from the 4-chamber view on 500 consecutive pregnancies at 19 to 24 weeks' gestation undergoing routine ultrasound examinations (100 pregnancies for each sonographer). Volumes were sent to the referral center, and 2 independent reviewers with experience in 4D fetal echocardiography assessed their quality in the display of the abdominal view, 4-chamber view, left and right ventricular outflow tracts, and 3-vessel and trachea view. Cardiac volumes were acquired in 474 of 500 pregnancies (94.8%). The 2 reviewers respectively acknowledged the presence of satisfactory images in 92.4% and 93.6% of abdominal views, 91.5% and 93.0% of 4-chamber views, in 85.0% and 86.2% of left ventricular outflow tracts, 83.9% and 84.5% of right ventricular outflow tracts, and 85.2% and 84.5% of 3-vessel and trachea views. The presence of a maternal body mass index of greater than 30 altered the probability of achieving satisfactory cardiac views, whereas previous maternal lower abdominal surgery did not affect the quality of reconstructed cardiac views. In conclusion, cardiac volumes acquired by 4D sonography in peripheral centers showed high enough quality to allow satisfactory diagnostic cardiac views.

Accuracy of four-dimensional spatiotemporal image correlation echocardiography in the prenatal diagnosis of congenital heart defects

OBJECTIVE

To evaluate the accuracy of four-dimensional (4D) spatiotemporal image correlation (STIC) echocardiography for the diagnosis of fetal congenital heart disease (CHD) in a selected high-risk population.

METHODS

Three hundred and sixty-three pregnant women referred for suspected CHD on screening ultrasound were evaluated by means of conventional echocardiography between 14 and 41 weeks' gestation and 4D-STIC volumes were obtained (including gray-scale and color Doppler information). Stored volumes were analyzed, at least 1 year after they had been acquired, by examiners blinded to the patients' identities and outcomes. The STIC diagnoses were compared to those made on conventional two-dimensional echocardiography and the accuracy of diagnosis was assessed with respect to postnatal examination, or autopsy in cases of termination of pregnancy or perinatal death.

RESULTS

The mean gestational age at volume acquisition was 24 + 5 weeks. STIC evaluation was possible in 98% of cases. Twenty-one cases were lost to follow-up, with a total of 167 normal hearts and 175 cases of CHD diagnosed at postnatal evaluation. The overall accuracy, sensitivity, specificity and positive and negative predictive values of STIC in determining the presence or absence of CHD were 91.6, 94.9, 88.1, 89.7 and 94.0%, respectively. Absolute concordance with the final specific diagnosis among cases with confirmed CHD was 74.3% for STIC echocardiography, compared with 81.7% for real-time evaluation.

CONCLUSION

4D-STIC echocardiography performed by experienced operators can be used in fetuses at risk for cardiac anomalies in order to reliably provide reassurance of normality or to accurately diagnose major structural heart defects.

Eleven fetal echocardiographic planes using 4-dimensional ultrasound with spatio-temporal image correlation (STIC): a logical approach to fetal heart volume analysis

BACKGROUND

Theoretically, a cross-sectional image of any cardiac planes can be obtained from a STIC fetal heart volume dataset. We described a method to display 11 fetal echocardiographic planes from STIC volumes.

METHODS

Fetal heart volume datasets were acquired by transverse acquisition from 200 normal fetuses at 15 to 40 weeks of gestation. Analysis of the volume datasets using the described technique to display 11 echocardiographic planes in the multiplanar display mode were performed offline.

RESULTS

Volume datasets from 18 fetuses were excluded due to poor image resolution. The mean visualization rates for all echocardiographic planes at 15-17, 18-22, 23-27, 28-32 and 33-40 weeks of gestation fetuses were 85.6% (range 45.2-96.8%, N = 31), 92.9% (range 64.0-100%, N = 64), 93.4% (range 51.4-100%, N = 37), 88.7%(range 54.5-100%, N = 33) and 81.8% (range 23.5-100%, N = 17) respectively.

CONCLUSIONS

Overall, the applied technique can favorably display the pertinent echocardiographic planes. Description of the presented method provides a logical approach to explore the fetal heart volumes.

Reliability of fetal cardiac volumetry using spatiotemporal image correlation: assessment of in-vivo and in-vitro measurements

OBJECTIVE

To assess the reliability of measurement of fetal cardiac ventricular volume, stroke volume, and ejection fraction with four-dimensional ultrasound using spatiotemporal image correlation (STIC).

METHODS

Volume datasets were collected from two sources: 24 from fetuses over a range of gestational ages and 12 from a miniature balloon model. Datasets were analyzed by three observers, repeatedly in 12 fetal datasets and all balloon datasets. Volume calculations were obtained by manually tracing multiple parallel slices (three-dimensional (3D) slice method). Measurement error was assessed by calculating standard errors of measurement (SEM) and coefficients of variation (CV). Reliability was assessed by calculating interobserver and intraobserver intraclass correlation coefficients (ICC).

RESULTS

Measurement errors of balloon volumes were small and reliability was good (SEM <or= 0.07 mL, ICC 0.98-1.00). Fetal ventricle volume measurement error ranged from 0.09 to 0.20 mL and CV from 14.6 to 28.3%. Ventricular volume reliabilities for intra- and interobserver comparisons were greater than or equal to 0.94 and 0.75, respectively. Fetal stroke volume measurement error (SEM 0.17 mL), CV (21.9%) and reliability were measured (intraobserver ICC: left ventricle stroke volume (LVSV), 0.93 vs. right ventricle stroke volume (RVSV), 0.88; interobserver ICC: LVSV, 0.75 vs. RVSV, 0.86). The measurement error decreased with increasing operator experience. The reliability of ejection fraction calculations was poor (ICC < 0.7) for intra- and interobserver comparisons.

CONCLUSIONS

Volume measurements obtained with STIC and 3D slice methods using a balloon model were reliable. In the fetus, measurement errors decreased with increasing operator experience, and reliability was better for stroke volume than for ejection fraction.

Three-dimensional fast acquisition with sonographically based volume computer-aided analysis for imaging of the fetal heart at 18 to 22 weeks' gestation

OBJECTIVE

The purpose of this study was to determine how frequently cardiac images derived from 3-dimensional (3D) volume sets, acquired by fast acquisition and evaluated with sonographically based volume computer-aided analysis (sonoVCAD), were satisfactory for prenatal screening at 18 to 22 weeks' gestation.

METHODS

A prospective study of 100 women with singleton pregnancies was undertaken. Three fast acquisition 3D volume sets were obtained from each patient. Four reviewers independently evaluated the 4-chamber and 5 extracted VCAD views. Factors contributing to unsatisfactory screening were also evaluated.

RESULTS

The frequency with which adequate views for cardiac screening could be obtained varied widely; some single views, such as that of the stomach, were well seen frequently, whereas others, such as the ductal arch, were well seen significantly less frequently (P < .05). A satisfactory screening examination, defined as a visualized 4-chamber, left ventricular outflow tract, right ventricular outflow tract, and axial stomach view, was obtained for 43% to 65% of patients (dependent on reviewer). Logistic regression revealed that obesity (odds ratio, 3.0; 95% confidence interval, 1.7-5.0) and a fetus with the spine toward the maternal abdomen (odds ratio, 1.7; 95% confidence interval, 1.1-2.5) were independently associated with an unsatisfactory screening examination

CONCLUSIONS

Three-dimensional fast acquisition volumes evaluated with sonoVCAD did not allow a satisfactory fetal cardiac screening examination to be obtained a high percentage of the time in a general obstetric population during the second trimester. Certain patient factors, such as body habitus and fetal position, are associated with unsatisfactory 3D imaging.

Satisfactory visualization rates of standard cardiac views at 18 to 22 weeks' gestation using spatiotemporal image correlation

OBJECTIVE

The purpose of this study was to determine the frequency with which 3 standard screening views of the fetal heart (4-chamber, left ventricular outflow tract [LVOT], and right ventricular outflow tract [RVOT]) can be obtained satisfactorily with the spatiotemporal image correlation (STIC) technique.

METHODS

A prospective study of 111 patients undergoing anatomic surveys at 18 to 22 weeks was performed. Two ultrasound machines with fetal cardiac settings were used. The best volume set that could be obtained from each patient during a 45-minute examination was graded by 2 sonologists with regard to whether the 4-chamber, LVOT, and RVOT images were satisfactory for screening.

RESULTS

All 3 views were judged satisfactory for screening in most patients: 1 sonologist graded the views as satisfactory in 70% of the patients, whereas the other found the views to be satisfactory in 83%. The position of the placenta did not alter the probability of achieving a satisfactory view, but a fetus in the spine anterior position was associated with a significantly lower probability that the views were regarded as satisfactory for screening (odds ratio, 0.28; 95% confidence interval, 0.09-0.70; P < .05).

CONCLUSIONS

This study suggests that STIC may assist with screening for cardiac anomalies at 18 to 22 weeks' gestation.