Application of three-dimensional ultrasonography in the evaluation of the fetal heart

Diagnostic value of echocardiography in fetal cardiac malformation and clinical classification

Diagnostic value of echocardiography in fetal cardiac malformation and clinical classification was investigated. In total, 206 high-risk parturients, who received a screening of prenatal fetal cardiac malformation in Jinan Maternity and Child Care Hospital from January 2015 to June 2017, were retrospectively analyzed, among those parturients, the results of labor induction or newborns of 141 parturients were diagnosed as cardiac malformation, the fetuses of 65 parturients were diagnosed as non-cardiac malformation, the detection of fetal cardiac malformation of all the parturients was carried out by two-dimensional ultrasound and four-dimensional ultrasound during gestation period, presence or absence of congenital cardiac malformation of the fetuses and clinical classification were estimated. The sensitivity of two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis was significantly higher than that of two-dimensional ultrasound diagnosis and four-dimensional ultrasound diagnosis (P<0.05). In addition, the sensitivity of four-dimensional ultrasound diagnosis was significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The specificity and positive predictive value of four-dimensional ultrasound diagnosis were significantly higher than those of two-dimensional ultrasound diagnosis and two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis (P<0.05). The diagnostic coincidence rates of four-dimensional ultrasound diagnosis and two-dimensional ultrasound diagnosis combined with four-dimensional ultrasound diagnosis were significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The negative predictive values of the combined ultrasound diagnosis and four-dimensional ultrasound diagnosis were significantly higher than that of two-dimensional ultrasound diagnosis (P<0.05). The diagnostic efficiency of two-dimensional ultrasound combined with four-dimensional ultrasound was good in the diagnosis of fetal cardiac malformation in prenatal period of pregnant women, it could improve detection rate of fetal cardiac malformation and is worthy of being generalized in clinic.

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.

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.

Usefulness of fetal three-dimensional ultrasonography for detecting of congenital heart defects and associated syndromes

Congenital heart defects (CHDs) occur in 1% of live-born infants and frequently are associated with extracardiac malformations. This study aimed to assess the feasibility and accuracy of three-dimensional ultrasonography (3DUS) in fetuses with CHD and to investigate whether 3DUS can add information about the heart and general fetal morphology that shows other congenital malformations or suggests syndromes. For 30 fetuses affected by CHD, 3DUS was performed using a Sonos 7500 ultrasound machine with a cardiac 3D transducer. In 44% of the exams, 3DUS was completely diagnostic for the CHD, providing additional information in 28% of the exams. Furthermore, 3DUS showed 82% of associated malformations, providing the complete diagnosis in 57% of the cases and helping with recognition of syndromes in others. The diagnostic accuracy of 3DUS was superior, with a higher number of acquisitions per exam. Performance was better in fetuses younger than 24 weeks for general morphologic details and in fetuses older than 24 weeks for the heart morphology.

Contemporary clinical applications of spatio-temporal image correlation in prenatal diagnosis

PURPOSE OF REVIEW

Four-dimensional fetal echocardiography has the potential to reduce the operator dependency of two-dimensional ultrasonography and increase the detection rate of congenital heart defects (CHDs). This review is intended to summarize recent evidence of the important role that four-dimensional ultrasonography with spatio-temporal image correlation (STIC) may play in the prenatal diagnosis of CHDs.

RECENT FINDINGS

Four-dimensional ultrasonography with STIC may provide the opportunity for telemedicine in the prenatal diagnosis of CHDs because four-dimensional volume datasets can be remotely acquired and accurately interpreted by different centers. Four-dimensional ultrasonography with STIC is an accurate and reproducible technique for the prenatal diagnosis of CHDs. Different four-dimensional rendering techniques can provide important insight into the spatial relationships of normal and abnormal fetal vascular structures.

SUMMARY

Four-dimensional fetal echocardiography with STIC may facilitate the examination of the fetal heart and could potentially increase the detection rate of CHDs.

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.

Collaborative study on 4-dimensional echocardiography for the diagnosis of fetal heart defects: the COFEHD study

OBJECTIVE

Congenital anomalies are the leading cause of infant mortality in the United States, and congenital heart defects (CHDs) are the most common type of birth defects. Recently, 4-dimensional ultrasonography (4DUS) with spatiotemporal image correlation (STIC) has been introduced for fetal echocardiography. Accumulating evidence indicates that 4DUS with STIC may facilitate the examination of the fetal heart. Our objectives were to determine the accuracy of 4DUS for the diagnosis of CHDs and the agreement among centers.

METHODS

This study included 7 centers with expertise in 4D fetal echocardiography. Fetuses with and without confirmed heart defects were scanned between 18 and 26 weeks, and their volume data sets were uploaded onto a centralized file transfer protocol server. Intercenter agreement was determined using a κ statistic for multiple raters.

RESULTS

Ninety volume data sets were randomly selected for blinded analysis. Overall, the median (range) sensitivity, specificity, positive and negative predictive values, and false-positive and -negative rates for the identification of fetuses with CHDs were 93% (77%-100%), 96% (84%-100%), 96% (83%-100%), 93% (79%-100%), 4.8% (2.7%-25%), and 6.8% (5%-22%), respectively. The most frequent CHDs were conotruncal anomalies (36%). There was excellent intercenter agreement (κ = 0.97).

CONCLUSIONS

(1) Four-dimensional volume data sets can be remotely acquired and accurately interpreted by different centers. (2) Among centers with technical expertise, 4DUS is an accurate and reliable method for fetal echocardiography.

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.

Three- and 4-dimensional ultrasonography in the prenatal evaluation of fetal anomalies associated with trisomy 18

OBJECTIVE

The purpose of this study was to assess the usefulness of 3- and 4-dimensional ultrasonography (3D/4DUS) for the description of anomalies associated with trisomy 18 and to determine whether 3D/4DUS adds diagnostic information over what is provided by conventional 2-dimensional ultrasonography (2DUS) alone.

METHODS

Twenty-six fetuses subsequently proven to have trisomy 18 underwent prenatal ultrasonographic evaluations by both 2DUS and 3D/4DUS. Volume data sets were acquired by the same sonographers after the conventional 2DUS examinations and were explored with 4-dimensional imaging software by another independent examiner blinded to the indications of 2DUS. The findings detected by 2DUS and 3D/4DUS were compared with those acquired at autopsy. The sensitivity of each modality for detecting anomalies was calculated and compared by the McNemar test.

RESULTS

Excluding polyhydramnios, there were 131 anomalies confirmed postnatally in 26 fetuses with trisomy 18. There was a statistically significant difference in the sensitivity for detecting anomalies between 3D/4DUS and 2DUS (93.89% versus 73.28%; McNemar value = 23.31; P < .05), especially in anomalies of the face/neck (96.15% versus 65.38%; McNemar value = 6.13; P < .05) and extremities (96.3% versus 48.15%; McNemar value = 11.07; P < .05). Three- and 4-dimensional ultrasonography provided additional diagnostic information for 83.97% of the anomalies related to trisomy 18 and influenced the obstetric management of 4 fetuses.

CONCLUSIONS

Three- and 4-dimensional ultrasonography offered diagnostic advantages for many anomalies associated with trisomy 18, especially for anomalies of the extremities and face. This modality could be a powerful adjunct to 2DUS in the prenatal anatomic evaluation of fetuses with trisomy 18.

The role of the sagittal view of the ductal arch in identification of fetuses with conotruncal anomalies using 4-dimensional ultrasonography

OBJECTIVE

Conotruncal anomalies represent one fifth of all congenital heart defects (CHDs) detected in the fetus. However, the spatial relationship of the great vessels is incorrectly defined in about 20% of these cases. The sagittal view of the ductal arch is considered a standard ultrasonographic view in fetal echocardiography and can be easily visualized using 4-dimensional (4D) ultrasonography. This study was designed to determine the role of this ultrasonographic plane for the prenatal diagnosis of conotruncal anomalies.

METHODS

We reviewed 4D volume data sets, acquired with the spatiotemporal image correlation technique, from fetuses with and without confirmed conotruncal anomalies. The visualization rate of the sagittal view of the ductal arch was compared among groups using standardized multiplanar views.

RESULTS

This study included 183 volume data sets from fetuses in the following groups: (1) normal echocardiographic findings (n = 130); (2) conotruncal anomalies (n = 18); and (3) other CHDs (n = 35). Volumes of poor image quality were excluded from analysis (8.2% [15/183]). The visualization rate of the sagittal view of the ductal arch was significantly lower in fetuses with conotruncal anomalies (5.6% [1/18]) than that in fetuses without abnormalities (93.1% [108/116]) and that in fetuses with other CHDs (79.4% [27/34]; P < .01). Absence of visualization of the sagittal view of the ductal arch was associated with a likelihood ratio of 9.44 (95% confidence interval, 5.8-15.5) to have conotruncal anomalies.

CONCLUSIONS

The sagittal view of the ductal arch may play an important role in the screening and prenatal diagnosis of conotruncal anomalies in 4D ultrasonography.

Changes in fetal cardiac geometry with gestation: implications for 3- and 4-dimensional fetal echocardiography

OBJECTIVE

Three- and 4-dimensional fetal echocardiography can be performed using novel algorithms. However, these algorithms assume that the spatial relationships among cardiac chambers and great vessels are constant throughout gestation. The objective of this study was to determine whether changes in fetal cardiac geometry occur during gestation.

METHODS

A cross-sectional study was conducted by reviewing 3- and 4-dimensional volume data sets from healthy fetuses obtained between 12 and 41 weeks of gestation. Volume data sets were examined using commercially available software. Parameters measured included angles between: (1) the ductal arch and fetal thoracic aorta; (2) the ductal arch and aortic arch; and (3) the left outflow tract and main pulmonary artery, as seen in the short axis of the heart. The mean angle from the left outflow tract to the short axis was calculated. Nonparametric statistics were used for analysis.

RESULTS

Eighty-five fetuses were included in the study. The angle between the ductal arch and the fetal thoracic aorta decreased with gestational age (Spearman rho coefficient: -0.39; P < .001). In contrast, the angle between the ductal arch and aortic arch, and the mean angle between the left outflow tract and the short axis of the heart increased with gestational age (Spearman rho coefficients: 0.45 and 0.40, respectively; P < .001).

CONCLUSIONS

(1) Changes in fetal cardiac geometry were shown with advancing gestational age. (2) Proposed algorithms for the examination of the fetal heart with 3-dimensional ultrasonography may need to be adapted to optimize visualization of the standard planes before 26 weeks of gestation.

Comparison of two- and three-dimensional ultrasonography in the evaluation of fetal heart: image quality and time spent in the exam

OBJECTIVES

To compare fetal heart evaluation done through two-dimensional (2DUS) and three-dimensional ultrasonography (3DUS) as to optimal plane imaging, image quality, and time needed to perform the examination.

METHODS

Prospective study involving 12 normal pregnant women, with gestational ages ranging from 22 to 26 weeks, scanned with a VOLUSON 730 with a convex 4.0-7.0 MHz transducer, in both two- and three-dimensional modes. In each case, three basic view planes were obtained: four-chambers view, right, and left ventricular outflow tracts. Each view was subjectively evaluated by three different examiners as to image quality, and graded from 0 (minimum) to 4 (maximum) cross-marks (+). The sum of all grades obtained for each case was used to classify the quality of the exam as unsatisfactory (0 to 1+), poor (2 to 4+), regular (5 to 7+), and good (8 to 12+). The time taken to obtain the views was recorded for each case, starting with the acquisition of the first view on the 2D exam and with the identification and opening of the volume blocks on the three-dimensional software.

RESULTS

The number of three-dimensional blocks with good, regular, poor, and unsatisfactory grades were, respectively, 6, 15, 9, and 10. The average in cross-marks of the cases graded good in each group without the worst result for each plane was 8. 2DUS was superior to 3DUS regarding the quality of the images obtained by the three pattern view planes and the average time to obtain high quality view planes was longer for 3DUS when compared to 2DUS. 2DUS offered better quality images and in less time than 3DUS.

CONCLUSIONS

Three-dimensional ultrasound is an advancement in fetal heart evaluation; however two-dimensional ultrasound remains the best screening method in diagnosing cardiac malformations, due to the good quality of its images and the lesser time needed to perform the exam.

A novel algorithm for comprehensive fetal echocardiography using 4-dimensional ultrasonography and tomographic imaging

OBJECTIVE

Tomographic ultrasound imaging (TUI) is a new display modality that allows simultaneous visualization of up to 8 parallel anatomic planes. This study was designed to determine the role of a novel algorithm combining spatiotemporal image correlation and TUI to visualize standard fetal echocardiographic planes.

METHODS

Volume data sets from fetuses with and without congenital heart defects (CHDs) were examined with a novel algorithm that allows simultaneous visualization of the 3-vessel and trachea view, the 4-chamber view, and outflow tracts. Visualization rates for these planes as well as the ductal arch and 5-chamber view were calculated.

RESULTS

(1) Two hundred twenty-seven volume data sets from fetuses without (n = 138) and with (n = 14) CHDs were reviewed; (2) among fetuses without CHDs, the 4-chamber view, 5-chamber view, ductal arch, 3-vessel and trachea view, left outflow tract, and short axis of the aorta were visualized in 99% (193/195), 96.9% (189/195), 98.5% (192/195), 88.2% (172/195), 93.3% (182/195), and 87.2% (170/195) of the volume data sets, respectively; (3) these views were visualized in 85% (17/20), 80% (16/20), 65% (13/20), 55% (11/20), 55% (11/20), and 70% (14/20) of the volume data sets, respectively, from fetuses with CHDs; and (4) simultaneous visualization of the short axis of the aorta, 3-vessel and trachea view, left outflow tract, and 4-chamber view was obtained in 78% (152/195) of the volume data sets from fetuses without CHDs and in 40% (8/20) of those with CHDs.

CONCLUSIONS

The 3-vessel and trachea view, the 4-chamber view, and both outflow tracts can be simultaneously visualized using a novel algorithm combining spatiotemporal image correlation and TUI.

Evolution of fetal ultrasonography

The authors wish to highlight the evolution that has occurred in fetal ultrasound in recent years. A first significant evolution lies in the increasing contribution of first trimester ultrasound for the detection of fetal anomalies. Malformations of several organs and systems have been diagnosed during the first trimester. Furthermore the systematic measurement of the fetal neck translucency has led to increasing rate of detection of aneuploidies and heart malformations. For several years now, three-dimensional (3D) and 4D ultrasound (US) have been used as a complementary tool to 2D US for the evaluation of fetal morphology. This brings an improved morphologic assessment of the fetus. Applications of the techniques are increasing, especially for the fetal face, heart and extremities. The third field where fetal US is continuously providing important information is the knowledge of the natural history of diseases. This has brought significant improvement in the postnatal management of several diseases, especially urinary tract dilatation and broncho-pulmonary malformation.

Four-dimensional ultrasonography of the fetal heart using a novel Tomographic Ultrasound Imaging display

OBJECTIVE

The objective of this study was to investigate the feasibility of examining the fetal heart with Tomographic Ultrasound Imaging (TUI) using four-dimensional (4D) volume datasets acquired with spatiotemporal image correlation (STIC).

MATERIAL AND METHODS

One hundred and ninety-five fetuses underwent 4D ultrasonography (US) of the fetal heart with STIC. Volume datasets were acquired with B-mode (n=195) and color Doppler imaging (CDI) (n=168), and were reviewed offline using TUI, a new display modality that automatically slices 3D/4D volume datasets, providing simultaneous visualization of up to eight parallel planes in a single screen. Visualization rates for standard transverse planes used to examine the fetal heart were calculated and compared for volumes acquired with B-mode or CDI. Diagnoses by TUI were compared to postnatal diagnoses.

RESULTS

(1) The four- and five-chamber views and the three-vessel and trachea view were visualized in 97.4% (190/195), 88.2% (172/195), and 79.5% (142/195), respectively, of the volume datasets acquired with B-mode; (2) these views were visualized in 98.2% (165/168), 97.0% (163/168), and 83.6% (145/168), respectively, of the volume datasets acquired with CDI; (3) CDI contributed additional diagnostic information to 12.5% (21/168), 14.2% (24/168) and 10.1% (17/168) of the four- and five-chamber and the three-vessel and trachea views; (4) cardiac anomalies other than isolated ventricular septal defects were identified by TUI in 16 of 195 fetuses (8.2%) and, among these, CDI provided additional diagnostic information in 5 (31.3%); (5) the sensitivity, specificity, positive- and negative-predictive values of TUI to diagnose congenital heart disease in cases where both B-mode and CDI volume datasets were acquired prenatally were 92.9%, 98.8%, 92.9% and 98.8%, respectively.

CONCLUSION

Standard transverse planes commonly used to examine the fetal heart can be automatically displayed with TUI in the majority of fetuses undergoing 4D US with STIC. Due to the retrospective nature of this study, the results should be interpreted with caution and independently confirmed before this methodology is introduced into clinical practice.

Three- and 4-dimensional ultrasound in obstetric practice: does it help?

OBJECTIVE

The purpose of this article was to review the published literature on 3-dimensional ultrasound (3DUS) and 4-dimensional ultrasound (4DUS) in obstetrics and determine whether 3DUS adds diagnostic information to what is currently provided by 2-dimensional ultrasound (2DUS) and, if so, in what areas.

METHODS

A PubMed search was conducted for articles reporting on the use of 3DUS or 4DUS in obstetrics. Seven-hundred six articles were identified, and among those, 525 were actually related to the subject of this review. Articles describing technical developments, clinical studies, reviews, editorials, and studies on fetal behavior or maternal-fetal bonding were reviewed.

RESULTS

Three-dimensional ultrasound provides additional diagnostic information for the diagnosis of facial anomalies, especially facial clefts. There is also evidence that 3DUS provides additional diagnostic information in neural tube defects and skeletal malformations. Large studies comparing 2DUS and 3DUS for the diagnosis of congenital anomalies have not provided conclusive results. Preliminary evidence suggests that sonographic tomography may decrease the examination time of the obstetric ultrasound examination, with minimal impact on the visualization rates of anatomic structures.

CONCLUSIONS

Three-dimensional ultrasound provides additional diagnostic information for the diagnosis of facial anomalies, evaluation of neural tube defects, and skeletal malformations. Additional research is needed to determine the clinical role of 3DUS and 4DUS for the diagnosis of congenital heart disease and central nervous system anomalies. Future studies should determine whether the information contained in the volume data set, by itself, is sufficient to evaluate fetal biometric measurements and diagnose congenital anomalies.

Three- and 4-dimensional ultrasound in obstetrics and gynecology: proceedings of the American Institute of Ultrasound in Medicine Consensus Conference

The American Institute of Ultrasound in Medicine convened a panel of physicians and scientists with interest and expertise in 3-dimensional (3D) ultrasound in obstetrics and gynecology to discuss the current diagnostic benefits and technical limitations in obstetrics and gynecology and consider the utility and role of this type of imaging in clinical practice now and in the future. This conference was held in Orlando, Florida, June 16 and 17, 2005. Discussions considered state-of-the-art applications of 3D ultrasound, specific clinical situations in which it has been found to be helpful, the role of 3D volume acquisition for improving diagnostic efficiency and patient throughput, and recommendations for future investigations related to the utility of volume sonography in obstetrics and gynecology.

New developments in fetal heart scanning: three- and four-dimensional fetal echocardiography

This article reviews the possibilities of three- and four-dimensional (3- and 4D) fetal echocardiography. A volume data set of a fetal heart can be acquired as a static volume, as a real-time 3D volume or as an offline 4D volume cine using spatial and temporal image correlation (STIC) software. STIC is explained and the potentials of this modality are emphasized. The display of a fetal heart volume data set demonstrates the cross-sections of interest, using the multiplanar mode or tomographic multislice imaging, and different volume rendering tools. The latter include: surface, minimum, inversion and glass body modes. This review highlights the potential of acquiring a digital volume data set of a heart cycle for later offline evaluation, either for an offline diagnosis, a second opinion (e.g. via Internet link) or for teaching fetal echocardiography to trainees and sonographers.

Three- and four-dimensional freehand fetal echocardiography: a feasibility study using a hand-held Doppler probe for cardiac gating

OBJECTIVE

To evaluate the clinical feasibility of the signal from a hand-held Doppler probe as a real-time tracking signal for dynamic three-dimensional (3D) (so-called four-dimensional (4D)) fetal echocardiography in a random patient cohort.

METHODS

Seventy fetuses, with and without congenital heart disease, at various gestational ages (mean, 25 weeks; range, 18-38 weeks) were investigated using freehand 3D echocardiography. Time gating was achieved concurrently by obtaining a Doppler signal of the fetal heart without further signal averaging. In 10 fetuses, Doppler gating was compared to cardiotocogram (CTG)-gated 3D echo using signal averaging. Gray-scale and color Doppler dynamic 3D displays and multiplanar views were assessed according to their ability to accurately depict cardiac gating and cardiac morphology.

RESULTS

In 68/70 fetuses, valid Doppler-based trigger signals were obtained. Correct cardiac gating was achieved in 231/275 (84%) 4D datasets. Doppler tracing of the fetal heart allowed beat-to-beat triggering without the necessity for signal averaging. Doppler gating detected rapid changes in the fetal heart rate more reliably than CTG gating, but was more sensitive to acoustic interference between the gating and echo-transducer when color-coded Doppler imaging was used. Image quality was highly dependent on random motion and the acoustic window. A total of 171/231 (74%) correctly gated datasets successfully demonstrated clinically useful 4D images of the fetal heart. The reconstruction of 3D and multiplanar views provided additional views not obtainable by two-dimensional imaging.

CONCLUSION

These results show that a hand-held Doppler probe can be used as a reliable online gating source for 4D fetal echocardiography.

Latest advances and topics in fetal echocardiography

PURPOSE OF REVIEW

Fetal diagnosis and the supporting specialties of perinatology, neonatology, and surgery have made rapid strides in the last decade. Numerous centers are focusing on this multifaceted niche area as the medical field realizes its vast promise and potential. The authors review some of the major advancements in thought and practice in the field of fetal echocardiography while attempting to give a less detailed overview for the less involved perinatologist.

RECENT FINDINGS

First trimester fetal echocardiography has been an area of recent interest as transducer technology improves. As a result, optimum timing of first and subsequent scans and the population profile they are to be applied to have become an issue that begs consensus. Three-dimensional and four-dimensional fetal echocardiography have also received a boost for the same reasons, and both are being studied for feasibility and accuracy. Fetal tissue Doppler and spectral Doppler imaging are potential areas for exploration; the early steps have been taken. Awareness of associated ultrasound markers, such as exaggerated nuchal translucency, as clues to the presence of congenital heart disease is important, even if controversial.

SUMMARY

The issue of missed prenatal diagnosis is disturbing, especially when it arises against a background of tremendous skill and technologic support. Strategies to minimize mistakes in this critical aspect need to be agreed on by the involved teams and put in place in a multidisciplinary manner if they are to have an important impact.

Three-dimensional (3D) and 4D color Doppler fetal echocardiography using spatio-temporal image correlation (STIC)

OBJECTIVE

Color Doppler echocardiography is used to visualize three transverse planes: the four-chamber, five-chamber, and three vessels and trachea views. Color Doppler spatio-temporal image correlation (STIC) is a new three-dimensional (3D) technique allowing the acquisition of a volume of data from the fetal heart that is displayed as a cineloop of a single cardiac cycle. The aim of the study was to examine the potential of color Doppler STIC to evaluate normal and abnormal fetal hearts.

METHODS

This prospective study included 35 normal fetuses and 27 fetuses with congenital heart defects (CHD) examined between 18 and 35 weeks of gestation. Volume acquisition was achieved by initiating the image capture sequence from the transverse four-chamber view. Volumes were stored for later offline evaluation using a personal computer-based workstation in a multiplanar mode and as spatial volume rendering.

RESULTS

Successful acquisition was possible in all 62 cases. The three planes could be demonstrated in 31/35 healthy fetuses and in 24/27 fetuses with CHD. Spatial volume rendering was attempted in 18 fetuses with CHD. In the four normal fetuses with inadequate visualization using color Doppler STIC, the region of interest was perpendicular to the ultrasound beam. In two fetuses with CHD inadequate visualization was related to an enlarged heart in late gestation, in which the entire cardiac volume could not be acquired. The third case was an 18-week fetus with complex CHD and transposed great vessels in which artifacts were related to confluent color signals as a result of low resolution in the reconstructed plane.

CONCLUSIONS

STIC in combination with color Doppler ultrasound is a promising new tool for multiplanar and 3D/4D rendering of the fetal heart. Limitations may be found later in gestation in fetuses with large hearts and early in gestation as a result of low discrimination of signals. In addition, insonation perpendicular to the structure of interest does not image color Doppler signals and should be avoided during acquisition.

Real-time 3-dimensional fetal echocardiography with an instantaneous volume-rendered display: early description and pictorial essay

OBJECTIVE

Random fetal motion, rapid fetal heart rates, and cumbersome processing algorithms have limited reconstructive approaches to 3-dimensional fetal cardiac imaging. Given the recent development of real-time, instantaneous volume-rendered sonographic displays of volume data, we sought to apply this technology to fetal cardiac imaging.

METHODS

We obtained 1 to 6 volume data sets on each of 30 fetal hearts referred for formal fetal echocardiography. Each volume data set was acquired over 2 to 8 seconds and stored on the system's hard drive. Rendered images were subsequently processed to optimize translucency, smoothing, and orientation and cropped to reveal "surgeon's eye views" of clinically relevant anatomic structures. Qualitative comparison was made with conventional fetal echocardiography for each subject.

RESULTS

Volume-rendered displays identified all major abnormalities but failed to identify small ventricular septal defects in 2 patients. Important planes and views not visualized during the actual scans were generated with minimal processing of rendered image displays. Volume-rendered displays tended to have slightly inferior image quality compared with conventional 2-dimensional images.

CONCLUSIONS

Real-time 3-dimensional echocardiography with instantaneous volume-rendered displays of the fetal heart represents a new approach to fetal cardiac imaging with tremendous clinical potential.

Four-dimensional ultrasonography of the fetal heart with spatiotemporal image correlation

OBJECTIVE

This study was undertaken to describe a new technique for the examination of the fetal heart using four-dimensional ultrasonography with spatiotemporal image correlation (STIC).

STUDY DESIGN

Volume data sets of the fetal heart were acquired with a new cardiac gating technique (STIC), which uses automated transverse and longitudinal sweeps of the anterior chest wall. These volumes were obtained from 69 fetuses: 35 normal, 16 with congenital anomalies not affecting the cardiovascular system, and 18 with cardiac abnormalities. Dynamic multiplanar slicing and surface rendering of cardiac structures were performed. To illustrate the STIC technique, two representative volumes from a normal fetus were compared with volumes obtained from fetuses with the following congenital heart anomalies: atrioventricular septal defect, tricuspid stenosis, tricuspid atresia, and interrupted inferior vena cava with abnormal venous drainage.

RESULTS

Volume datasets obtained with a transverse sweep were utilized to demonstrate the cardiac chambers, moderator band, interatrial and interventricular septae, atrioventricular valves, pulmonary veins, and outflow tracts. With the use of a reference dot to navigate the four-chamber view, intracardiac structures could be simultaneously studied in three orthogonal planes. The same volume dataset was used for surface rendering of the atrioventricular valves. The aortic and ductal arches were best visualized when the original plane of acquisition was sagittal. Volumes could be interactively manipulated to simultaneously visualize both outflow tracts, in addition to the aortic and ductal arches. Novel views of specific structures were generated. For example, the location and extent of a ventricular septal defect was imaged in a sagittal view of the interventricular septum. Furthermore, surface-rendered images of the atrioventricular valves were employed to distinguish between normal and pathologic conditions. Representative video clips were posted on the Journal's Web site to demonstrate the diagnostic capabilities of this new technique.

CONCLUSION

Dynamic multiplanar slicing and surface rendering of the fetal heart are feasible with STIC technology. One good quality volume dataset, obtained from a transverse sweep, can be used to examine the four-chamber view and the outflow tracts. This novel method may assist in the evaluation of fetal cardiac anatomy.

Dynamic free-hand three-dimensional fetal echocardiography gated by cardiotocography

OBJECTIVE

To evaluate the clinical feasibility of conventional cardiotocography (CTG) as a cardiac cycle triggering signal for three-dimensional (3D) fetal echocardiography.

METHOD

Free-hand 3D echocardiography was performed on a total of 25 fetuses with and without congenital heart disease at various gestational ages (mean, 29 weeks; range, 19-35 weeks). Simultaneously, online CTG was used for time gating. Gray-scale and color Doppler dynamic 3D displays, as well as multiplanar views, were assessed for their ability to depict the cardiac morphology and correct cardiac gating.

RESULTS

Valid CTG-based trigger signals could be obtained in 24 of the 25 fetuses. Correct cardiac gating was achieved in 101 of the 111 (91%) 3D datasets. Color Doppler imaging of blood flow in four dimensions was possible in 34 of 36 (94%) datasets. Reconstructed 3D and multiplanar views provided additional views not available in two-dimensional (2D) imaging. Acoustic interference between the CTG transducer and echotransducer could be reduced by the use of a high-frequency echotransducer, second-harmonic frequency imaging and appropriate positioning of the two transducers. Imaging quality was highly dependent on the quality of 2D images and random motion artifacts.

CONCLUSIONS

CTG can be used as an online gating source for dynamic 3D fetal echocardiography.

New dimensions and directions in fetal cardiology

PURPOSE OF REVIEW

The purpose of this review is to describe several of the most relevant and exciting recent advances in the field of fetal cardiology.

RECENT FINDINGS

First, the prenatal detection of congenital heart disease has improved, and continues to improve, with the increasingly widespread incorporation of the four-chamber view and outflow tracts into the routine screening fetal ultrasound evaluation. Second, increasingly sophisticated computer processing systems and improvements in imaging technology have enabled the development of automated three-dimensional ultrasound imaging systems that promise to revolutionize both the prenatal detection and diagnosis of congenital heart disease. Conventional two-dimensional imaging approaches may soon become obsolete. Third, there has been an increasing ability to intervene successfully prenatally not only for fetal arrhythmias and heart failure, but also for some forms of structural heart disease. In some cases of left or right ventricular outflow tract obstruction, early intervention during the second trimester may prevent the development of ventricular hypoplasia. Finally, several recent studies suggest that prenatal diagnosis may improve neonatal outcome for fetuses with congenital heart disease. The growing ability to intervene prenatally has the potential to improve neonatal outcome still further.

SUMMARY

These critical and exciting developments in fetal cardiology promise to increase fetal echocardiography's clinical impact dramatically during the years to come.