4D fetal echocardiography-An update

Dual-modal Photoacoustic and Ultrasound Imaging: from preclinical to clinical applications

Photoacoustic imaging is a novel biomedical imaging modality that has emerged over the recent decades. Due to the conversion of optical energy into the acoustic wave, photoacoustic imaging offers high-resolution imaging in depth beyond the optical diffusion limit. Photoacoustic imaging is frequently used in conjunction with ultrasound as a hybrid modality. The combination enables the acquisition of both optical and acoustic contrasts of tissue, providing functional, structural, molecular, and vascular information within the same field of view. In this review, we first described the principles of various photoacoustic and ultrasound imaging techniques and then classified the dual-modal imaging systems based on their preclinical and clinical imaging applications. The advantages of dual-modal imaging were thoroughly analyzed. Finally, the review ends with a critical discussion of existing developments and a look toward the future.

Prenatal diagnosis of fetal conotruncal defects by using 2D ultrasound and HD live flow combined with spatiotemporal image correlation

INTRODUCTION

To explore the diagnostic value of spatiotemporal image correlation (STIC) for different types of fetal conotruncal defects (CTDs).

METHODS

The clinical data and STIC images of 174 fetuses with CTDs diagnosed via prenatal ultrasound were analyzed retrospectively.

RESULTS

Among the 174 cases of CTDs, 58 were tetralogy of Fallot (TOF); 30, transposition of great arteries (TGA) (D-TGA, 23 cases; cc-TGA, 7 cases); 26, double outlet of the right ventricle (DORV); 32, persistent arterial trunk (PTA) (type A1, 15 cases; type A2, 11 cases; type A3, 5 cases; type A4, 1 case); and 28, pulmonary atresia (PA) (ventricular septal defect, 24 cases; ventricular septal integrity, 4 cases). Among the cases, 156 were complicated with complex congenital intracardiac and extracardiac malformations. The abnormal display rate of the four-chamber view of two-dimensional echocardiography was low. The display rate of the permanent arterial trunk was the highest (90.6%) in STIC imaging.

CONCLUSIONS

STIC imaging can be used in the diagnosis of different types of CTDs, especially in persistent arterial trunks, and thus has great value for the clinical treatment and prognosis of these defects.

Clinical value of prenatal ultrasound in diagnosis and classification of common arterial trunk

OBJECTIVES

To investigate the clinical value of prenatal ultrasound in the diagnosis of the common arterial trunk (CAT) classification and associated malformations.

MATERIALS AND METHODS

The 2D ultrasound images, spatiotemporal image correlations (STICs) and clinical data of 88 fetuses diagnosed with CAT malformations by prenatal ultrasound were retrospectively analyzed and classified. The correlation between different types, fetal malformation and pregnancy outcomes were analyzed.

RESULTS

Among the 88 fetuses, there were 39 cases (44.32%) of type A1, 40 cases (45.45%) of type A2, 8 cases (9.09%) of type A3, and 1 case of type A4 (1.14%). There were 16 cases (18.18%) with isolated CAT, 48 cases (54.55%) with complex intra-cardiac structural abnormalities, and 24 cases (27.27%) with intra-cardiac and extra-cardiac structural abnormalities. In extra-cardiac structural malformations, 14 cases were associated with 1 other system abnormality, 4 cases with 2 other system abnormalities, 3 cases with 3 other system abnormalities, while 3 cases were combined with 4 other system abnormalities, among which the facial and physical abnormalities had the highest incidence (39.13%). The STIC images were completely displayed in all 88 cases. There was a statistical difference between isolated CAT and CAT combined with other abnormalities in fetal pregnancy outcomes.

CONCLUSIONS

Prenatal ultrasound had a high clinical application value in CAT classification. Pregnancy outcomes were highly correlated with the classification and associated intra-cardiac and extra-cardiac structural malformations. The early evaluation of fetal prognosis before birth has important value for clinical intervention.

Fetal cardiac function evaluation: A review

The aim of this review is to provide an up to date on the current use of fetal echocardiography in assessing the fetal cardiac function and its potential research and clinical applications. Despite classically is been used for prenatal diagnosis of fetal heart defects, assessment of fetal cardiac function has been recently proposed as a fundamental tool to assess pregnancies complicated by several disorders with long-term impact on post-natal cardiovascular health, such as placental insufficiency and fetal growth restriction. In this review we present anatomical and functional fetal cardiac development mechanisms and an overview of the currently available techniques for evaluating fetal heart function.

Improvement of diagnostic efficiency in fetal congenital heart disease using fetal intelligent navigation echocardiography by less-experienced operators

OBJECTIVE

This study investigated the feasibility and accuracy of fetal intelligent navigation echocardiography (FINE) for the prenatal diagnosis of congenital heart disease (CHD) by inexperienced and experienced operators.

METHOD

In this prospective study, all volume data sets from 120 fetuses with a broad spectrum of CHD were acquired using spatiotemporal image correlation technology. The prenatal diagnostic procedures were performed by two operators with different experience (beginner: 1 year and expert: 15 years) using FINE and traditional fetal echocardiography. Data were analyzed on the time of examination and acquisition of results.

RESULTS

Diagnoses made by FINE and traditional echocardiography were completely consistent with the final diagnosis of CHD in 98 (81.66%) versus 20 (16.66%) (P < 0.001) beginners and 87.50% (n = 105) versus 101 (84.16%) experts, respectively. On the contrary, there was significant difference using traditional echocardiography (16.66% versus 84.16%, P < 0.001) by two examiners. Furthermore, the examination time decreased when using FINE compared with using traditional echocardiography (beginner operators: 4.54 ± 1.03 min versus 20.58 ± 3.36 min, P < 0.001; expert operators: 3.89 ± 0.96 min versus 12.73 ± 1.62 min, P < 0.001).

CONCLUSION

Based on our results, a prenatal diagnosis of CHD can be made with high feasibility and accuracy using FINE compared with traditional fetal echocardiography for beginner operators.

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.

Feasibility of 4D-Spatio Temporal Image Correlation (STIC) in the Comprehensive Assessment of the Fetal Heart Using FetalHQ®

Fetal Heart Quantification (FetalHQ®) is a novel speckle tracking software that permits the study of global and regional ventricular shape and function from a 2D four-chamber-view loop. The 4D-Spatio Temporal Image Correlation (STIC) modality enables the offline analysis of optimized and perfectly aligned cardiac planes. We aimed to evaluate the feasibility and reproducibility of 4D-STIC speckle tracking echocardiography (STE) using FetalHQ® and to compare it to 2D STE. We conducted a prospective study including 31 low-risk singleton pregnancies between 20 and 40 weeks of gestation. Four-chamber view volumes and 2D clips were acquired with an apex pointing at 45° and with a frame rate higher than 60 Hz. Morphometric and functional echocardiography was performed by FetalHQ®. Intra- and interobserver reproducibility were evaluated by the intraclass correlation coefficient (ICC). Our results showed excellent reproducibility (ICC > 0.900) for morphometric evaluation (biventricular area, longitudinal and transverse diameters). Reproducibility was also good (ICC > 0.800) for functional evaluation (biventricular strain, Fractional Area Change, left ventricle volumes, ejection fraction and cardiac output). On the contrary, the study of the sphericity index and shortening fraction of the different ventricular segments showed lower reproducibility (ICC < 0.800). To conclude, 4D-STIC is feasible, reproducible and comparable to 2D echocardiography for the assessment of cardiac morphometry and function.

Noninvasive Dual-Modality Photoacoustic-Ultrasonic Imaging to Detect Mammalian Embryo Abnormalities after Prenatal Exposure to Methylmercury Chloride (MMC): A Mouse Study

BACKGROUND

Severe environmental pollution and contaminants left in the environment due to the abuse of chemicals, such as methylmercury, are associated with an increasing number of embryonic disorders. Ultrasound imaging has been widely used to investigate embryonic development malformation and dysorganoplasia in both research and clinics. However, this technique is limited by its low contrast and lacking functional parameters such as the ability to measure blood oxygen saturation (SaO 2 ) and hemoglobin content (HbT) in tissues, measures that could be early vital indicators for embryonic development abnormality. Herein, we proposed combining two highly complementary techniques into a photoacoustic-ultrasound (PA-US) dual-modality imaging approach to noninvasively detect early mouse embryo abnormalities caused by methylmercury chloride (MMC) in real time.

OBJECTIVES

This study aimed to assess the use of PA-US dual-modality imaging for noninvasive detection of embryonic toxicity at different stages of growth following prenatal MMC exposure. Additionally, we compared the PA-US imagining results to traditional histological methods to determine whether this noninvasive method could detect early developmental defects in utero.

METHODS

Different dosages of MMC were administrated to pregnant mice by gavage to establish models of different levels of embryonic malformation. Ultrasound, photoacoustic signal intensity (PSI), blood oxygen saturation (SaO 2 ), and hemoglobin content (HbT) were quantified in all experimental groups. Furthermore, the embryos were sectioned and examined for pathological changes.

RESULTS

Using PA-US imaging, we detected differences in PSI, SaO 2 , HbT, and heart volume at embryonic day (E)14.5 and E11.5 for low and high dosages of MMC, respectively. More important, our results showed that differences between control and treated embryos identified by in utero PA-US imaging were consistent with those identified in ex vivo embryos using histological methods.

CONCLUSION

Our results suggest that noninvasive dual-modality PA-US is a promising strategy for detecting developmental toxicology in the uterus. Overall, this study presents a new approach for detecting embryonic toxicities, which could be crucial in clinics when diagnosing aberrant embryonic development. https://doi.org/10.1289/EHP8907.

Prenatal diagnosis of congenital heart defects: echocardiography

Congenital heart defects (CHD) are the most common congenital anomaly, and the majority can be diagnosed during prenatal life. Prenatal detection rates remain highly variable, as most CHD occur in low risk pregnancies and therefore depend on the maternal obstetric provider to recognize fetal cardiac abnormality on obstetric screening anatomic ultrasound. Fetuses with abnormal findings on obstetric screening anatomic ultrasound and/or risk factors for cardiac disease should be referred for evaluation with fetal echocardiography. Fetal echocardiography should be performed by specialized sonographers and interpreted by physicians with knowledge of evolving fetal cardiac anatomy and physiology throughout gestation. A fetal echocardiography examination, which can be done from the late first trimester onward, utilizes a standardized and systemic approach to diagnose fetuses with CHD or other forms of primary or secondary cardiac disease. The field of fetal cardiology has advanced past the accurate prenatal diagnosis of simple and complex CHD, as fetal echocardiography enables understanding of dynamic fetal cardiac physiology and consideration of potential fetal/neonatal treatment. The greatest impact of fetal echocardiography remains identification of critical CHD before birth to allow immediate cardiac management after delivery to decrease neonatal morbidity and mortality. Analyzing the severity of abnormal cardiac physiology in various forms of CHD before birth allows the fetal cardiologist to prognosticate effects on the developing fetus, predict risk of postnatal hemodynamic instability, guide delivery planning through multidisciplinary collaboration, and anticipate how the disease will impact the neonate after delivery.

Prevalence and clinical significance of fetal tricuspid regurgitation during the third trimester of pregnancy

Abstract Objectives: the aim of this study was to determine the prevalence of fetal tricuspid valve regurgitation (TR) during the third trimester of low-risk pregnancies and to assess its clinical significance on neonates. Methods: this is a cross-sectional study including 330 singleton fetuses referred for routine fetal echocardiography during 3rd trimester in a fetal medicine center in Recife, Brazil. The presence and degree of tricuspid regurgitation were analyzed. Whenever TR was identified on fetal echocardiography, postnatal data, including the results of postnatal echocardiography were reviewed. Results: the prevalence of tricuspid regurgitation was 10.0% (n=33) in the study population. Regarding regurgitation degree, 90.9% (n=30) presented mild regurgitation and none presented important TR. Postnatal data was obtained from 21 neonates. Twenty of them were discharged without any complications, and one presented respiratory distress due to prematurity. Transthoracic echocardiography was performed in 66.7% (n=14) of the neonates and it was normal in 92.9% (n=13) of them. One neonate, 7.1%, persisted with tricuspid regurgitation, but had no other findings. Conclusions: tricuspid regurgitation in fetuses with normal cardiac anatomy during the 3rd trimester is a common condition in low-risk pregnancies, and is not associated with cardiac abnormalities or need for neonatal intervention.

Fetal speckle-tracking echocardiography: a comparison between two-dimensional and electronic spatio-temporal image correlation (e-STIC) technique

BACKGROUND

Speckle tracking technology has been applied to assess ventricular deformation throughout the cardiac cycle. An electronic four dimensional probe that allows rapid acquisition of electronic spatio-temporal image correlation volumes (eSTIC) has been recently introduced.

OBJECTIVES

The aim of our study was to investigate whether e-STIC acquisition improves deformation analyses reproducibility.

STUDY DESIGN

We recruited fetuses between 20 and 40 weeks of gestation. We obtained a 2D video clip and an e-STIC volume of a four-chamber view. We focused on left ventricular global strain (LV-GS) and left ventricular ejection fraction (LV-FE). Intraobserver, interobserver and intermethod agreement were assessed by means of intraclass correlation coefficient (ICC) and illustrated by Bland-Altman plots. Systematic differences between measurements were assessed using a paired t-test.

RESULTS

The mean difference between LV-GS values obtained with e-STIC and 2D analysis was -0.10 (95% CI -2.28, 2.08). No systematic differences were found between the two techniques for LV-GS values (p-value = .927). The mean difference between LV-FE values obtained with e-STIC and 2D analysis was 7.55 (95% CI 4.16, 10.95; p-value <.001). The inter-rater reliability of LV-GS was moderate-to-substantial for both e-STIC and 2D. The inter-rater reliability of LV-FE obtained via e-STIC was superior to that obtained via 2D analysis. The intra-rater reliability of LV-GS obtained with e-STIC was superior to that obtained with 2D analysis (ICC 0.857; 95% IC 0.761-0.917). The intra-rater reliability of LV-FE obtained via e-STIC was superior to that obtained via 2D analysis (ICC 0.647; IC 0.51-0.783).

CONCLUSIONS

e-STIC seems to be a better technique than 2D analysis for intra-rater reliability of LV-GS. 4D acquisition might improve intrinsic limitations of speckle tracking echocardiography.

Prenatal evaluation of fetal atrioventricular valves by real-time 4D volume imaging with electronic matrix probe

Background

The purpose of this study is to evaluate the feasibility using real-time four-dimensional (RT 4D) volume imaging with electronic matrix probe to observe the morphology of atrioventricular valves in normal and abnormal fetuses, measure the area and circumference of atrioventricular valves in normal fetuses and analyze the correlation with gestational age.

Methods

RT 4D volume imaging with electronic matrix probe was used to collect cardiac volume data of 162 normal fetuses with the gestational age from 22 to 32 weeks and 19 fetuses with atrioventricular valves abnormalities were also enrolled. All the volume data were analyzed and processed in real-time. The morphology of mitral and tricuspid valves was observed in surface mode. The area and circumference of valves were measured in a 4D render view at the end of diastole and analyzed the correlation with gestational age.

Results

In 148 of 162 fetuses (91%), the 4D rendered image could be successfully obtained, which clearly showed the morphology of the atrioventricular valves. The area and circumference of mitral and tricuspid valves were positively correlated with gestational age (P < 0.01). Furthermore, 4D rendered images were successfully obtained in 17 of 19 fetuses (89%) with atrioventricular valves abnormalities.

Conclusions

The reference range of the area and circumference of atrioventricular valves in normal fetuses at different gestational weeks could be determined by using the RT 4D volume imaging with electronic matrix probe, which can provide certain diagnostic information for the clinic. The RT 4D images could display the valves morphology vividly in both normal and abnormal fetuses, including some subtle lesions which are not identified by traditional two-dimensional (2D) echocardiography. It is feasible to use the RT 4D volume imaging with electronic matrix probe to perform the prenatal evaluation in the fetal atrioventricular valves.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12947-021-00240-7.

Fetal Vascular Rings and Pulmonary Slings: Strategies for Two- and Three-Dimensional Echocardiographic Diagnosis

Fetal aortic arch anomalies and pulmonary slings can be difficult to accurately diagnose but have important clinical implications related to vascular rings, congenital heart disease, and chromosomal anomalies. In this article, the authors briefly review the embryology and development of the fetal arch to facilitate understanding of its diverse variants. Two-dimensional echocardiographic characteristics are summarized for each type of these malformations to propose a strategy for fetal diagnosis. The added benefits of three-dimensional echocardiography with spatiotemporal image correlation are also shown. Finally, the authors propose a strategy for volume acquisition and postanalysis to spur postanalysis clinical use of this technology.

The construction and application of an ultrasound and anatomical cross-sectional database of structural malformations of the fetal heart

OBJECTIVES

Establish a fetal heart anatomical cross-sectional database that correlates with screening transverse ultrasound images suggested by international professional organizations to detect congenital heart defects.

METHODS

Fetuses with suspected congenital heart defects identified using the following cardiac image sequences obtained from transverse slices beginning from the upper abdomen and ending in the upper thorax were the subjects of this study: (1) four-chamber view, (2) left ventricular outflow tract view, (3) three-vessel right ventricular outflow tract view, and (4) the three-vessel tracheal view. A database of digital two-dimensional images of the transverse sweep was created for fetuses with confirmed congenital heart defects. In addition, using four-dimensional ultrasound spatial-temporal image correlation, selected transverse ultrasound images were acquired as part of the database. Ultrasound-detected congenital heart defects were confirmed postnatally from pathological specimens of the heart and lungs using a cross-sectional technique that mirrored the ultrasound images described above. When anatomical specimens were not available, prenatal ultrasound-detected congenital heart defects were confirmed using postnatal echocardiography and/or following surgery.

RESULTS

The four screening views described in the Methods section identified 160 fetuses that comprised the database. Forty-five datasets consisted of both ultrasound and anatomical cross-sectional images. Thirteen percent (6/45) only had abnormalities of the four-chamber view (eg, endocardial cushion defects). Twenty-four percent (11/45) had abnormalities of the four-chamber view as well as right and left outflow tracts (eg, complex malformations). Of these, 10 of 11 had an abnormal tracheal view. Sixteen percent (7/45) had an abnormal four-chamber view and abnormal right outflow tract (eg, pulmonary stenosis). Thirty-three percent (15/45) had a normal four-chamber view but had abnormal right and left outflow tracts as well as an abnormal tracheal view (eg, tetralogy of Fallot, D-transposition of the great arteries).

CONCLUSIONS

Combining both ultrasound and anatomical imaging may be of assistance in training imagers to recognize cardiovascular pathology when performing the screening examination of the fetal heart.

Electronic versus conventional spatiotemporal image correlation (STIC) fetal echocardiography: a direct comparison

Objectives: Recent advances in Spatial Temporal Image Correlation (STIC) 4 D fetal echocardiography include the application of eSTIC based on electronic probe image acquisition. We aimed to directly compare the performance of conventional STIC versus eSTIC technique (B-Mode and color Doppler imaging) during off-line reconstruction of STIC/eSTIC fetal heart volume pairs.Methods: Pairs of B-Mode and Color Doppler STIC volumes were acquired sequentially by firstly conventional (STIC) followed by electronic (eSTIC) probes during 33 consecutive obstetric scans at median 23 (range 13-31) gestational weeks. The resulting 66 fetal heart volume pairs were assessed blindly off-line by a fetal cardiologist who documented feasibility of reconstruction, presence of motion artifacts, subjective image quality on a 4-level scale: 1-best to 4-non-diagnostic and morphological diagnosis, to enable a paired comparison of STIC and eSTIC in the same fetus under similar scanning conditions.Results: eSTIC volumes had higher temporal resolution (37 vs. 24 frames per second, p < .001), less motion during acquisition (12 vs. 20 cases, O.R. 7.0, p = .002) and better average image quality (1.9 vs. 2.2, p = .006) compared to STIC volumes. More diagnostic reconstructions were achieved by eSTIC (n = 55, 86%) than STIC (n = 52, 78.8%), p = .001), in a comparable analysis time (mean 4.96 vs. 4.94 min). During a comparison of image quality of the original acquisition (A) and reconstructed planes (B and C planes) e STIC was superior in 22 (33%), 39 (59%) and 21 (38%) volumes, respectively, with the remaining cases being of similar quality (<10% in each plane in favor of STIC). Imaging mode and gestational age had a similar impact on both eSTIC and STIC performance: diagnostically acceptable studies in 49 (75.8%) vs. 48 (72.2%) by B-Mode, 60 (90.9%) vs. 56 (84.8%) by Color Doppler Mode, 8 (62.5%) vs. 10 (50%) in early scans, 38 (95%) vs. 38 (95%) in mid-gestation scans, and 7 (70%) vs. 6 (60%) in third trimester scans. Eight obstetric scans identified a fetus with a cardiac variant or structural abnormality. Diagnostic concordance of the two STIC approaches was comparable (40/48 concordant interpretations, kappa 0.657) all confirmed by fetal and/or postnatal echocardiography.Conclusions: eSTIC was associated with more effective 4 D fetal heart reconstruction due to reduced motion artifacts and superior image quality in all planes, when compared to STIC. Early gestation reconstructions were not generally successful using either technology. Further study is needed to define the cost-effectiveness and diagnostic impact of eSTIC over conventional STIC and their role over, or in addition to, screening 2 D fetal echocardiography by appropriately trained sonographers.

An In-depth Perspective of Aortic Arch Branching in Fetal Vascular Rings Using Spatiotemporal Image Correlation Combined With High-definition Flow Imaging: Report of 4 Cases

On the basis of 2-dimensional fetal echocardiographic findings, we investigated 4 different fetal vascular ring cases using spatiotemporal image correlation (STIC) combined with high-definition (HD) flow imaging. An in-depth 3-dimensional perspective of aortic arch branching (ie, the brachiocephalic arteries) was created by application of glass body and HDlive flow rendering algorithms (GE Healthcare, Zipf, Austria). Additionally, complete (U- or O-shaped) or incomplete (C-shaped) vascular rings were clearly differentiated in utero, and articulations around the trachea and esophagus were more easily imaged. In conclusion, spatiotemporal image correlation combined with HD flow imaging could classify fetal vascular rings with accuracy and facilitate decision making during postnatal management.

Introduction: From fetal echocardiography to fetal cardiology: A journey of over half a century

In this Special Issue of the Journal, 8 review articles that represent the new developments and applications of fetal echocardiography and fetal cardiology for diagnosis, prognosis, and treatment of fetal cardiovascular disease are included. The goal was to provide an updated review of the evidence for the current and emerging use of fetal echocardiography and cardiac magnetic resonance, improved diagnosis of challenging congenital heart disease, new tools for evaluation of fetal systolic and diastolic function, better prognosis and risk stratification of newborns with congenital heart diseases, and new and promising therapies for fetuses with cardiovascular disease.