Three- and four-dimensional reconstruction of the aortic and ductal arches using inversion mode: a new rendering algorithm for visualization of fluid-filled anatomical structures

Prenatal Diagnosis and Fetopsy Validation of Complete Atrioventricular Septal Defects Using the Fetal Intelligent Navigation Echocardiography Method

(1) Background: Artificial Intelligence (AI) is a modern tool with numerous applications in the medical field. The case series reported here aimed to investigate the diagnostic performance of the fetal intelligent navigation echocardiography (FINE) method applied for the first time in the prenatal identification of atrioventricular septal defects (AVSD). This congenital heart disease (CHD) is associated with extracardiac anomalies and chromosomal abnormalities. Therefore, an early diagnosis is essential to advise parents and make adequate treatment decisions. (2) Methods: Four fetuses diagnosed with AVSD via two-dimensional (2D) ultrasound examination in the second trimester were enrolled. In all cases, the parents chose to terminate the pregnancy. Since the diagnosis of AVSD with 2D ultrasound may be missed, one or more four-dimensional (4D) spatiotemporal image correlation (STIC) volume datasets were obtained from a four-chamber view. The manual navigation enabled by the software is time-consuming and highly operator-dependent. (3) Results: FINE was applied to these volumes and nine standard fetal echocardiographic views were generated and optimized automatically, using the assistance of the virtual intelligent sonographer (VIS). Here, 100% of the four-chamber views, and after the VISA System application the five-chamber views, of the diagnostic plane showed the atrioventricular septal defect and a common AV valve. The autopsies of the fetuses confirmed the ultrasound results. (4) Conclusions: By applying intelligent navigation technology to the STIC volume datasets, 100% of the AVSD diagnoses were detected.

Assessment of Fetal Congenital Heart Diseases by 4-Dimensional Ultrasound Using Spatiotemporal Image Correlation: Pictorial Review

The aim of this pictorial review is to describe the technical advances achieved through the application of 4-dimensional (4D) ultrasound using spatiotemporal image correlation (STIC) over conventional 2-dimensional ultrasound in the prenatal detection of congenital heart disease (CHD). Spatiotemporal image correlation is a volume imaging technique that simplifies fetal heart studies while providing more diagnostic information than is typically available from traditional 2-dimensional studies. Four-dimensional software allows the study of cardiac anatomy and function during a single cardiac cycle and has greatly contributed to diagnostic enhancement of CHD. Color flow and power Doppler can be added to STIC in the study of vessel anatomy and to increase the detection of ventricular septal defects. Anatomical details of the fetus can be displayed in multiple images such as using computed tomography or magnetic resonance imaging. In addition, cardiac anatomy can be sectioned freely and reconstructed using different reformatting applications. Realistic views of the fetal heart, with particular emphasis on myocardium and endocardium cushion, can be reached using novel lightening techniques. Moreover, using 4D ultrasound, echolucent structures can be converted into solid voxels generating "digital casts" of the fetal heart that enhances the understanding of the great vessel relationships in the ventricular inflow and outflow tracts. Recently, sillhouette mode has shown to improve depth perception and resolution compared with conventional 3D power Doppler in the study of inflow and outflow tracts. Here, a gallery of prenatally detected CHD using 4D ultrasound with STIC and different applications is described.

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.

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

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

4D Fetal Echocardiography in Clinical Practice

Spatiotemporal image correlation (STIC) is a technique that acquires the fetal cardiac volumes, and then analyzes it offline in both multiplanar and rendered modes, using both static and moving images from a four-dimensional (4D) cine sequence simulating a full cardiac cycle. Spatiotemporal image correlation makes it possible to evaluate cardiac structures and their vascular connections, is less operator dependent, and allows cardiac volumes to be sent to specialists in tertiary centers for examination. Spatiotemporal image correlation can be combined with other software techniques, such as virtual organ computer-aided analysis (VOCAL) and automatic volume calculation (SonoAVC), to calculate cardiac function parameters. It can also be used in association with Omniview® in order to obtain standard echocardiographic planes using simple targets arterial rendering (STAR) and four-chamber view and swing technique (FAST). Recently, fetal intelligent navigation echocardiography (FINE), acquired from 3D STIC volumes, has made it possible to automatically obtain nine standard echocardiographic planes. In this article, we review the chief applications of 4D echocardiography using STIC technique in clinical practice.

How to cite this article

Araujo Júnior E, Tedesco GD, Carrilho MC, Peixoto AB, Carvalho FHC. 4D Fetal Echocardiography in Clinical Practice. Donald School J Ultrasound Obstet Gynecol 2015;9(4): 382-396.

Four-dimensional echocardiography with spatiotemporal image correlation and inversion mode for detection of congenital heart disease

The aim of this study was to evaluate the use of 4-D echocardiography with inversion mode and spatiotemporal image correlation (IM-STIC) in the detection of normal and abnormal fetal hearts. We retrospectively studied 112 normal fetuses and 16 fetuses with a confirmed diagnosis of congenital heart disease. Two volumes were acquired from each of the fetuses using transverse and sagittal sweeps. Volumes were reconstructed with IM-STIC. In normal fetuses, IM-STIC facilitated visualization of the interior structures of the fetal heart and great vessels. The visualization rates of intended planes obtained from IM-STIC 4D data ranged from 55% to 100%. In 16 fetuses with congenital heart disease, IM-STIC was able to display the cardiac malformations using digital casting. Some of the malformations were suspected during pre-natal 2-D echocardiography, and their pre-natal IM-STIC diagnoses were confirmed by post-natal echocardiography, surgery and/or autopsy. Hence, 4-D IM-STIC allows better visualization of complex congenital heart disease and should be considered a very useful addition to 2-D echocardiography.

Screening of congenital heart disease in the second trimester of pregnancy: current knowledge and new perspectives to the clinical practice

OBJECTIVE

Congenital heart diseases are common in foetuses, with an incidence greater than six times that of chromosomal abnormalities; however, experts in cardiac anatomy have evaluated only the foetuses of pregnant women with increased risk for congenital heart disease. Over the years, it has become clear that congenital heart disease occur in foetuses of low-risk women. In the mid-1980s, a proposal to expand the assessment of cardiac anatomy was presented to obstetricians in order to improve prenatal screening. With the aim to systematise and improve the diagnosis of congenital heart disease in foetuses, the International Society of Ultrasound in Obstetrics and Gynecology established an ultrasound heart examination guideline. In this review, we have described the important features of this guideline and discussed the applications of this tool in clinical practice.

METHODS

We performed a literature search of the National Library of Medicine for publications released between 2000 and 2012; we used search terms pertinent to congenital heart disease, such as foetal echocardiography, foetal heart and cardiac screening examination.

RESULTS

The guidelines serve as a standard and help to systematise the screening for congenital heart diseases, but we think that some topics may be added to design the most appropriate screening method. However, we cannot expand the topics to be evaluated in this examination without good training of sonographers who undergo this screening.

CONCLUSION

Although the screening standardisation is a good tool to be used in day-to-day practice, the increment of aortic and ductal archs and colour Doppler to heart screening could be useful to detect further cardiac defects.

Recent advances in sonographic imaging of fetal thoracic structures

Recent ultrasonographic methods applied in the evaluation of fetal thoracic structures and anomalies are presented. Fetal lung volumetric assessment by 3D ultrasonography, analysis of the thoracic wall by 3D-rendered image and 3D skeletal-mode imaging, intrathoracic vessel evaluation by 3D power Doppler ultrasonography, analysis of heart anatomy and abnormalities by 4D spatiotemporal image correlation, identification of normal and abnormal intrathoracic almost isoechogenic structures by volume contrast imaging and evaluation of the heart and great vessels by 3 and 4D inverse mode will be reviewed.

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.

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.

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.

Four-dimensional volume-rendered imaging of the fetal ventricular outflow tracts and great arteries using inversion mode for detection of congenital heart disease

AIM

Using four-dimensional (4D) sonography with an inversion mode, we evaluated fetal ventricular outflow tracts and great vessels for the detection of congenital heart disease.

METHODS

Volume datasets of the fetal heart were acquired with spatiotemporal image correlation (STIC), which uses automated transverse and longitudinal sweeps of the anterior chest wall. A total of 12 normal fetuses and seven fetuses with congenital heart disease (one case of double-outlet right ventricle, one case of tetralogy of Fallot, one case of transposition of the great arteries, one case of hypoplastic pulmonary artery with a large ventricular septal defect, and three cases of hypoplastic left heart syndrome) at 16-37 weeks of gestation were studied using transabdominal 4D sonography with an inversion mode. 4D inversion mode images of great arteries were evaluated.

RESULTS

4D ultrasound with an inversion mode demonstrated real-time 3D angiographic features of fetal cardiac outflow tracts in both normal and abnormal fetal hearts. This modality facilitated visualization of the relationships, size, and course of the outflow tracts, thus helping the examiner to more effectively understand the spatial relationships between the vessels. In normal fetal hearts, it was clearly shown that the pulmonary artery crosses in front of the aorta. In the three cases of hypoplastic left heart syndrome, an extremely small ascending aorta was evident. In the one case of tetralogy of Fallot, a relatively small pulmonary artery was noted. In the one case of hypoplastic pulmonary artery with a large ventricular septal defect, a markedly small main pulmonary artery was depicted. In the case of transposition of the great arteries, the vessels left the ventricles parallel to each other. In the case of double-outlet right ventricle, great arteries leaving the right ventricle in parallel were shown.

CONCLUSION

4D ultrasound in the inversion mode provides a means of evaluating fetal cardiac outflow tracts in 3D in real time. This technique may assist in the evaluation of spatial relationships between the great vessels and both ventricles, and the difference in the size of great vessels. Moreover, the inversion mode images should be more readily discernible than those obtained by conventional ultrasonography. 4D ultrasound in the inversion mode may be an important modality in future fetal cardiac research and in the evaluation of fetal congenital heart disease.

Fetal interrupted aortic arch: 2D-4D echocardiography, associations and outcome

OBJECTIVES

To analyze fetal two-dimensional (2D) echocardiographic characteristics of interrupted aortic arch (IAA) and its different types, to explore whether the use of 4D ultrasound with B-flow imaging and spatiotemporal image correlation (STIC) can improve prenatal diagnostic accuracy, and to describe associations and outcome.

METHODS

The study comprised IAA fetuses examined exclusively by 2D conventional echocardiography during the period from 1994 to 2003, and those identified by conventional echocardiography and examined further by 4D ultrasound with B-flow imaging and STIC during the period January 2004 to July 2008, identified among fetuses examined at two referral centers for congenital heart defects (CHD). Postnatal follow-up was available in all cases. Karyotyping and fluorescent in-situ hybridization (FISH) analysis for the DiGeorge critical region (22q11.2) were performed in all cases.

RESULTS

Twenty-two cases of isolated IAA (15 Type B and seven Type A, seven and three of which, respectively, underwent B-flow imaging and STIC) were detected among 2520 cases of fetal CHD. In seven of the 15 Type B cases, a right subclavian artery arose anomalously (ARSA). 2D echocardiography failed to distinguish the type of IAA in only two cases and the ARSA in five of the seven cases. B-flow imaging and STIC successfully identified IAA types in all 10 cases examined and clearly visualized the origin and course of the ARSA, including cervical ones. FISH detected 22q11.2 microdeletion in 10 of the 15 Type B cases and an unusual association with Type A in one of the seven cases. Fetal/neonatal outcome included: eight terminations of pregnancy, one intrauterine death and four postoperative deaths in the neonatal period, and nine neonates were alive after surgery at a mean follow-up time of 58 months (range, 4 months-13 years).

CONCLUSION

Our results confirm the feasibility of prenatal characterization of IAA and its different types based on 2D echocardiographic examination, albeit with some limitations in the thorough assessment. 4D ultrasound with B-flow imaging and STIC can apparently facilitate visualization and detailed examination of the anatomical features of the IAA types, including visualization of the neck vessels, thus supplying additional information with respect to 2D sonography. As for the known association with microdeletion 22q11.2, our data indicate that Types A and B are distinct, there being a close association only with IAA Type B.

Three and four dimensional ultrasound: a novel method for evaluating fetal cardiac anomalies

OBJECTIVE

To evaluate the role of various new models of 3- and 4-dimensional (3D and 4D) ultrasound (US) applications in prenatal assessment of fetal cardiac anomalies.

METHODS

Volume data sets of 81 fetuses with fetal cardiac anomalies, as previously diagnosed by 2D US, were acquired by 3D and cine 4D using spatiotemporal image correlation (STIC) software. Various additional rendering tools were applied. Color, power, high definition Doppler and B-flow were added to the volumes acquired. A retrospective offline analysis of the cardiac defects was performed.

RESULTS

The mean gestational age at diagnosis was 24 weeks (range 13-38); 128 anomalies were detected and were classified into the following categories: I, Situs anomalies in 8 cases; II, abnormal four-chamber view in 63 cases; III, outflows tract anomalies in 27 cases; IV, arches anomalies in 21 cases; and V, veins anomalies in 9 cases. Rendering tools differed in each groups of anomalies.

CONCLUSIONS

Fetal cardiac anomalies can be evaluated adequately by the information gained by 3D and 4D volumes obtained by STIC. Since no single module is sufficiently accurate for the diagnosis of all cardiac anomalies, each of the cardiac anomaly categories requires different and appropriate module of visualization.

A primer for fetal cardiac imaging: a stepwise approach for 2-dimensional imaging

Detection of congenital heart disease (CHD) remains problematic, even with advances in imaging. Imaging modalities, such as magnetic resonance imaging, have been helpful in better understanding certain abnormalities, such as the fetal central nervous system. However, because of cardiac motion, screening and detection of CHD are best performed by sonography. Although newer technical advances in sonography, including 3-dimensional (3-D) dynamic multiplanar imaging and Doppler techniques, are extremely helpful in better delineating CHD, the mainstay of detection of CHD remains 2-D real-time imaging. Understanding 2-D imaging of the heart, using multiple views, is necessary to perform any type of multiplanar imaging as both require basic understanding of the same basic views. Although it is beyond the scope of this article to review all facets of fetal cardiac imaging, we will present a stepwise approach using 2-D imaging in the detection of CHD.

Semi-automatic segmentation of fetal cardiac cavities: progress towards an automated fetal echocardiogram

OBJECTIVE

To develop a novel application of a tool for semi-automatic volume segmentation and adapt it for analysis of fetal cardiac cavities and vessels from heart volume datasets.

METHODS

We studied retrospectively virtual cardiac volume cycles obtained with spatiotemporal image correlation (STIC) from six fetuses with postnatally confirmed diagnoses: four with normal hearts between 19 and 29 completed gestational weeks, one with d-transposition of the great arteries and one with hypoplastic left heart syndrome. The volumes were analyzed offline using a commercially available segmentation algorithm designed for ovarian folliculometry. Using this software, individual 'cavities' in a static volume are selected and assigned individual colors in cross-sections and in 3D-rendered views, and their dimensions (diameters and volumes) can be calculated.

RESULTS

Individual segments of fetal cardiac cavities could be separated, adjacent segments merged and the resulting electronic casts studied in their spatial context. Volume measurements could also be performed. Exemplary images and interactive videoclips showing the segmented digital casts were generated.

CONCLUSION

The approach presented here is an important step towards an automated fetal volume echocardiogram. It has the potential both to help in obtaining a correct structural diagnosis, and to generate exemplary visual displays of cardiac anatomy in normal and structurally abnormal cases for consultation and teaching.

Current applications of fetal cardiac imaging technology

PURPOSE OF REVIEW

Over the last few years, great progress has been made in imaging technology, which is changing the way prenatal visualization of the fetal heart is used for diagnosis and therapy.

RECENT FINDINGS

This paper reviews recent clinical research using these new techniques, namely dynamic three-dimensional (4D) echocardiography, myocardial Doppler imaging, B-flow ultrasonography, endoscopic ultrasound, and magnetic resonance imaging. Of them, 4D echocardiography is the most significant development and is discussed in greater detail. This includes real-time volumetric data acquisition using matrix-array transducer technology, motion artefact elimination using spatio-temporal image correlation, and various display options. The advantages and limitations of each are also addressed.

SUMMARY

These techniques can provide (1) sequential assessment of the entire heart using a full 4D dataset, (2) 4D delineation of trabeculation patterns on the ventricular walls, en-face dynamic shapes of ventricular septal defects and spatially complex malformations, (3) derivation of cardiac indices to myocardial contractility and strain rate by Doppler tissue imaging, and/or (4) the use of transoesophageal ultrasound to guide in-utero cardiac intervention. All of these techniques expand our ability to evaluate the morphology and function of the in-utero heart.

The use of inversion mode and 3D manual segmentation in volume measurement of fetal fluid-filled structures: comparison with Virtual Organ Computer-aided AnaLysis (VOCAL)

OBJECTIVE

Volume measurements by three-dimensional (3D) ultrasonography are considered more accurate than those performed by two-dimensional (2D) ultrasonography. The purpose of this study was to compare the agreement of three techniques, as well as the inter- and intraobserver agreements for volume measurements of fetal fluid-filled structures.

METHODS

Fifty 3D volume datasets of fetal stomachs and bladders were explored. Volume measurements were performed independently by two observers using: (1) Virtual Organ Computer-aided AnaLysis (VOCAL); (2) inversion mode; and (3) 'manual segmentation'. Reliability was evaluated using intraclass correlation coefficient (ICC), and Bland-Altman plots were generated to examine bias and agreement. The time required to complete the measurements was compared using Student's t-test or the Wilcoxon Signed Rank Test, and P-values < 0.025 or < 0.05 were considered statistically significant.

RESULTS

All volume datasets could be measured using the three techniques. A high degree of reliability was observed between: (1) VOCAL and inversion mode (ICC, 0.995; 95% CI, 0.992-0.997); (2) VOCAL and manual segmentation (ICC, 0.997; 95% CI, 0.995-0.998); and (3) inversion mode and manual segmentation (ICC, 0.995; 95% CI, 0.992-0.997). There was good agreement between VOCAL and inversion mode (mean, - 2.4%; 95% limits of agreement, - 20.1 to 15.3%), VOCAL and manual segmentation (mean, - 8.3%; 95% limits of agreement, - 28.8 to 12.2%) as well as between inversion mode and manual segmentation (mean, 5.9%, 95% limits of agreement: - 14.3 to 26%). Manual segmentation and inversion mode measurements were obtained significantly faster than those by VOCAL.

CONCLUSIONS

Volume measurements of fetal fluid-filled structures of relatively regular shape with inversion mode and manual segmentation are feasible. Both techniques have good agreement with VOCAL and are significantly faster than VOCAL. Inversion mode is a reliable method for volume calculations of fluid-filled organs, whereas manual segmentation can be used when volume measurements by VOCAL or inversion mode are technically difficult to obtain, such as solid structures with poorly defined borders as the volume dataset is rotated, like the uterine cervix.

A systematic approach to the use of the multiplanar display in evaluation of abnormal vascular connections to the fetal heart using 4-dimensional ultrasonography

OBJECTIVE

The multiplanar display is a modality that allows the simultaneous visualization of 3 orthogonal planes from volume data sets obtained with 3- and 4-dimensional ultrasonography. Simultaneous display of standard views used in fetal echocardiography and their orthogonal planes may provide novel ultrasonographic views for examination of the fetal heart and its vascular connections. This study was designed to determine the clinical utility of the multiplanar display in the examination of abnormal vascular connections to the fetal heart.

METHODS

We reviewed 4-dimensional volume data sets, acquired with the spatiotemporal image correlation technique, from patients with abnormal vascular connections to the fetal heart. Multiplanar views of the fetal heart were used to simultaneously display standard planes used in fetal echocardiography and their corresponding orthogonal planes.

RESULTS

This study included 4 volume data sets from fetuses with confirmed abnormal vascular connections to the heart, including: (1) an interrupted inferior vena cava with azygos or hemiazygos vein continuation; (2) a persistent left superior vena cava draining into a dilated coronary sinus; and (3) a dilated superior vena cava associated with a thoracic lymphangioma. Simultaneous visualization of orthogonal planes displaying abnormal vascular connections to the fetal heart facilitated identification of the abnormal vessels and their spatial relationships with other vascular structures.

CONCLUSIONS

Multiplanar imaging can be used to assess abnormal vascular connections to the fetal heart and may provide novel ultrasonographic planes for fetal echocardiography using 3- and 4-dimensional ultrasonography.

Potential pitfalls and methods of improving in utero diagnosis of transposition of the great arteries, including the baby bird's beak image

OBJECTIVE

The goal of this study was to analyze our recent experience with fetuses with transposition of the great arteries (TGA) to identify potential pitfalls and possible methods to better detect conotruncal anomalies such as TGA.

METHODS

We analyzed all nonreferral obstetric ultrasound examinations in which we performed basic, targeted, or formal fetal echocardiography with a newborn diagnosis of TGA.

RESULTS

Nine neonates had TGA. Five of these cases were diagnosed prenatally, and 4 of these had complex congenital heart abnormalities. In these 4 cases, there were abnormalities in the cardiac axis (n = 3), abnormal valves or ventricular size (n = 2), and ventricular septal defects (n = 3) that were detected on the 4-chamber view of the heart. In all cases that were not detected prenatally, both prospective and retrospective reviews of the 4-chamber heart appeared normal. The prospective analyses of the outflow tracts were all interpreted as normal, whereas the retrospective review showed subtle abnormalities such as the "baby bird's beak" image. In review of these cases, there was failure to show the "crisscross" relationship of the outflow tracts. In 1 case, 5 short axis views of the heart, retrospectively showed the artery originating from the left ventricle and bifurcated, representing the pulmonary artery.

CONCLUSIONS

Transposition of the great arteries may be associated with complex cardiac disease that could be detected on the 4-chamber view of the heart. When the 4-chamber view is normal, it is important to identify the crisscross relationship of the outflow tracts. If this is not done, it is important to document that the pulmonary artery bifurcates and originates from the right ventricle. Five short axis views of the heart may be helpful to detect conotruncal abnormalities.

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.

Fetal cardiac ventricle volumetry in the second half of gestation assessed by 4D ultrasound using STIC combined with inversion mode

OBJECTIVE

Quantification of fetal heart ventricle volume can aid in the evaluation of functional and anatomical aspects of congenital heart disease. The aim of this study was to establish nomograms for ventricular volume using three-dimensional (3D) inversion mode ultrasonography with the spatio-temporal image correlation (STIC) modality and to calculate ejection fraction and stroke volume.

METHODS

The fetal heart was scanned using the STIC modality, during fetal quiescence with abdomen uppermost, at an angle of 30-50 degrees , without color Doppler flow mapping. In post-processing, starting with the classic four-chamber view plane in the A-frame, the reference point was moved to the center of the ventricle. The operator used the edit volume followed by Virtual Organ Computer-aided AnaLysis (VOCAL) mode options; in manual trace the VOCAL settings were set to 15 degrees . The trace was drawn and included the myocardium; inversion mode thresholding provided the volume of the intraventricular (anechoic) voxels within the region of interest. The total volume and the intraventricular volume were displayed. The process was repeated for right (R) and left (L) ventricles at end diastole (EDV) and end systole (ESV). The stroke volume (SV = EDV - ESV) and ejection fraction (EF = SV/EDV) were calculated from these measurements. Intraclass correlation was used to evaluate intra- and interobserver agreement.

RESULTS

One hundred fetuses ranging from 20 + 5 to 40 + 0 gestational weeks were included in the study. In addition, six fetuses diagnosed during the study period with a cardiac anomaly were examined and their ventricular volumes compared with those of the main study group. LEDV ranged from a mean of 0.53 cm(3) at midgestation to a mean of 3.96 cm(3) at term. LESV ranged from a mean of 0.17 cm(3) at midgestation to 1.56 cm(3) at term. REDV ranged from a mean of 0.68 cm(3) at midgestation to a mean of 5.44 cm(3) at term. RESV ranged from a mean of 0.26 cm(3) at midgestation to 2.29 cm(3) at term. Total stroke volume ranged from a mean of 0.78 cm(3) at midgestation to a mean of 5.5 cm(3) at term. The mean right : left ventricle ratio was 1.4, and left ejection fraction ranged from 42.5 to 86% in these fetuses. Nomograms were created for RESV, LESV, REDV, LEDV and total stroke volumes vs. estimated fetal weight and gestational age. Intra- and interobserver agreement reached 96%.

CONCLUSIONS

3D inversion mode sonography combined with STIC represents a simple and reproducible method for estimating fetal cardiac ventricle volume. This innovative methodology may add to overall evaluation of cardiac volume and function, and improve our understanding of normal and abnormal cardiac structure, as well as the severity and prognosis of cardiac lesions.

Assessment of the third-trimester fetus using 3-dimensional volumes: a pilot study

PURPOSE

To examine whether the third-trimester fetus can be assessed sonographically using 3-dimensional (3D) volume data sets.

METHODS

Twenty-seven consecutive third-trimester fetuses were evaluated. Fetuses were scanned using 2-dimensional (2D) imaging followed by 5 3D volume acquisitions. The initial scan was interpreted and reported based on the 2D images. The 3D volume data sets were independently reviewed offline several weeks later by 2 sonologists. Parameters evaluated included fetal presentation, placental location, amniotic fluid volume, fetal biometry including a calculation of estimated fetal weight, and major fetal anatomic structures. The result of the interpretation via 3D reconstruction of the volume from each of the 2 sonologists was compared with the original 2D sonography report.

RESULTS

Fetal presentation, amniotic fluid volume, and placental location with respect to the cervix were correctly identified 100% of the time by each sonologist. The estimated fetal weight was within 10% of the 2D estimate 89% (95% CI, 0.71-0.98) of the time for sonologist A and 96% (95% CI, 0.81-0.99) of the time for sonologist B. The majority of major anatomic landmarks were adequately seen by both sonologists.

CONCLUSION

Offline review of 3D volume data sets is a reliable method for determining fetal presentation, amniotic fluid volume, placental location, and estimating fetal weight in the third trimester.

Three-Dimensional Echocardiography for Studies of the Fetal Heart: Present Status and Future Perspectives

Three-dimensional (3D) ultrasound of the fetal heart is increasingly being used in prenatal diagnosis. While very detailed fetal cardiac studies can be performed using the various 3D ultrasound modalities, their utility for screening for fetal heart disease is yet to be proven. With the emergence of even newer technologies such as quantification techniques and two-dimensional matrix arrays, further improvements are imminent.

How useful is 3D and 4D ultrasound in perinatal medicine?

AIM

The purpose of this paper is to review and analyze the published literature on the use of three-dimensional (3DUS) and four-dimensional (4DUS) ultrasound in perinatal medicine.

METHODS

We systematically searched Medline through PubMED (January 2000-January 2006), including EMBASE/Excerpta Medica database as well as the Cochrane Database of Systematic Reviews. The search terms used to identify clinical application of 3DUS and 4DUS studies in perinatal medicine were technical development, special features, and recommendation for fetal imaging, research on 3DUS or 4DUS, and the usage of invasive 3DUS or 4DUS procedures. The reference bibliographies of relevant books were also manually searched for supplementary citations. Inclusion criteria were as follows: (1) studies related to the use of 3DUS or 4DUS in perinatal medicine; (2) full text were available in English; (3) publication format of original scientific articles, case reports, editorials or literature reviews and chapters in the books.

RESULTS

Five hundred and seventy-five articles were identified, and among those, 438 were relevant to this review.

CONCLUSIONS

3DUS and 4DUS provided additional information for the diagnosis of facial anomalies, evaluation of neural tube defects, and skeletal malformations. Additional research is needed to determine the clinical utility of 3DUS and 4DUS for the diagnosis of congenital heart disease, central nervous system (CNS) anomalies and detection of fetal neurodevelopmental impairment assessed by abnormal behavior in high-risk fetuses.

3D and 4D ultrasound in fetal cardiac scanning: a new look at the fetal heart

Over the last decade we have been witness to a burgeoning literature on three-dimensional (3D) and four-dimensional (4D) ultrasound-based studies of the fetal cardiovascular system. Recent advances in the technology of 3D/4D ultrasound systems allow almost real-time 3D/4D fetal heart scans. It appears that 3D/4D ultrasound in fetal echocardiography may make a significant contribution to interdisciplinary management team consultation, health delivery systems, parental counseling, and professional training. Our aim is to review the state of the art in 3D/4D fetal echocardiography through the literature and index cases of normal and anomalous fetal hearts.

Inversion Mode Display of 3D Sonography: Applications in Obstetric and Gynecologic Imaging

OBJECTIVE

Three-dimensional sonography involves volume acquisitions of sonographic data that can be displayed in a variety of ways, including surface rendering and multiplanar reconstruction. A new method of displaying sonographic volumes is called the inversion mode, which displays the cystic portions within the entire volume as echogenic areas. The gray-scale portion of the image becomes transparent, and the cystic areas become brightly visible in three dimensions.

CONCLUSION

This article shows the applications for this method of volume sonography display and shows the importance of being able to visualize all of the cystic areas concurrently within a volume.

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.

The role of spatio-temporal image correlation (STIC) with tomographic ultrasound imaging (TUI) in the sequential analysis of fetal congenital heart disease

OBJECTIVE

Spatio-temporal image correlation associated with the tomographic ultrasound imaging mode (TUI-STIC) is a new modality that allows a complete sequential analysis of cardiac structures to be displayed on a single panel by showing all echocardiographic transverse views at the same time. The aims of this study were to identify the best settings for displaying the classic echocardiographic views at different gestational ages and to investigate the role of TUI-STIC in the sequential segmental analysis of complex congenital heart disease (CHD).

METHODS

Four-dimensional volumes from 103 cases of confirmed fetal CHD diagnosed and managed at our referral center were evaluated using TUI-STIC. To select the best interslice distance for adequate display of the central cardiovascular connections, each volume was opened and the TUI mode activated, having as a reference the apical four-chamber view. The number of slices was set at nine. The volume was then scrolled until the most significant echocardiographic views were displayed on the screen windows. Then, if too many windows showed intermediate non-diagnostic views, the slice distance was adjusted finely until all key echocardiographic views showed up in the various windows. The interslice distance was regressed against gestational age and the best-fitting curve was identified.

RESULTS

A sequential segmental analysis could be shown with TUI-STIC in all cases. A linear regression equation best fitted the correlation between interslice distance and advancing gestational age (r(2) = 0.9042), with the mean interslice distance being 2.7 (SD, 0.3) mm at 19-23 gestational weeks, and 4.0 (SD, 0.4) mm at 30-33 weeks. These settings allowed a complete sequential analysis in all cases.

CONCLUSIONS

TUI-STIC allows a complete sequential analysis of CHD in the fetus. The most suitable interslice distances for all gestational ages could be identified. These data may be used while adopting this imaging modality in the four-dimensional evaluation of fetal CHD.

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.

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-dimensional and four-dimensional fetal echocardiography: a new frontier

PURPOSE OF REVIEW

One of the difficulties of conventional two-dimensional cardiac imaging is the inability to examine fetal cardiac anatomy from multiple angle planes. Three-dimensional and four-dimensional ultrasound allows the fetal examiner to more accurately accomplish this task. Currently, multiple disciplines may be involved in the examination of the fetal heart (pediatric cardiologists, obstetricians, maternal-fetal medicine specialists, and radiologists). The three-dimensional and four-dimensional imaging equipment used by these specialty physicians varies greatly. The purpose of this communication is to review techniques using three-dimensional and four-dimensional imaging that the pediatric cardiologist may not be exposed to in the clinical environment, however, in consulting with colleagues needs to have an understanding of these imaging modalities.

RECENT FINDINGS

The reconstruction of cardiac structures using this technology allows the examiner to view cardiac anatomy in a manner that was limited by previous two-dimensional imaging. Volume datasets are obtained in the three-dimensional static mode (no cardiac motion) or using four-dimensional - the three-dimensional heart is observed contracting during one or multiple cardiac cycles. Therefore, the fourth dimension is time. Using either three-dimensional or four-dimensional technology datasets are acquired, followed by image reconstruction. The image reconstruction enables the examiner to evaluate a two-dimensional image using multiple views, evaluate intracardiac anatomy at different depth planes, and recreate casts of blood flow of the chambers and great vessels.

SUMMARY

This new technology has enhanced the ability of the examiner to identify normal and complex fetal heart anatomy during the early second to the late third trimesters of pregnancy.

Three-dimensional inversion rendering: a new sonographic technique and its use in gynecology

OBJECTIVE

The purpose of this presentation is to describe the use of the 3-dimensional (3D) sonographic inversion rendering mode in displaying fluid-filled structures using dedicated hardware and software in gynecology.

METHODS

The 3D software used inverts anechoic into echogenic voxels, which, against the black background of the monitor screen, display the fluid-filled structure as a "cast" of it. The technique of the rendering process is described. Three-dimensional sonographic volumes of the adnexal area in 3 patients thought to have adnexal or ovarian masses were stored and rendered with the use of the laptop version of the inversion software. The same process was used in an additional 12 women for various indications: 7 with suspected uterine malformations and 5 with uterine bleeding. Of these 12 women, 11 underwent saline infusion sonohysterography.

RESULTS

Rendering the inverted fluid-filled adnexal structures revealed that, in all 3 cases, they were tubal, not ovarian, in origin (chronic hydrosalpinges). Of the 7 uterine cavities suspected of malformation, 3 were normal and 4 had uterine malformations: 2 arcuate uteri and 2 incomplete septate uteri. Of the 4 woman with dysfunctional uterine bleeding, 3 had endometrial cavities with polyps and 1 had an irregular surface of the cast. One woman with postmenopausal spotting had an enlarged but otherwise normal cavity.

CONCLUSIONS

After a relatively short learning curve to master the inversion rendering technique, it is possible to use it in a selected number of gynecologic cases with fluid-filled structures. In resolving the correct diagnosis of the adnexal masses, the inversion images performed better than the 2-dimensional (2D) and 3D orthogonal planes. For diagnosis of uterine disease, the inversion pictures presented marginal value over the 2D and 3D images. The 3D inversion rendering technique may have added value in selected gynecologic cases, establishing a more accurate diagnosis somewhat faster than only 2D sonography or even the 3D orthogonal planes.

A novel method to improve prenatal diagnosis of abnormal systemic venous connections using three- and four-dimensional ultrasonography and 'inversion mode'

OBJECTIVE

The precise prenatal diagnosis of abnormal venous connections of the fetal heart is challenging. Anatomical accuracy may be important in determining the best route for postnatal angiography, as well as the prognosis and treatment. This study was designed to determine the value of 'inversion mode', a new three- and four-dimensional (4D) rendering algorithm, in the visualization of the spatial relationships of an interrupted inferior vena cava (IVC) with azygos or hemiazygos vein continuation associated with and without heterotaxic syndromes.

METHODS

Heart volumes were acquired using 4D ultrasonography and spatiotemporal image correlation in cases of interrupted IVC with azygos/hemiazygos continuation (n = 3). Volume datasets were rendered using the 'inversion mode' algorithm and abnormal images were compared to those generated from a library of normal fetuses.

RESULTS

The 'inversion mode' rendering algorithm allowed the visualization of dilated azygos or hemiazygos veins and their spatial relationships with the descending aorta, the aortic arch, the superior vena cava, and the atria in cases of interrupted IVC with and without heterotaxic syndromes.

CONCLUSIONS

The 'inversion mode' algorithm improves prenatal visualization of both dilated azygos and hemiazygos veins, as well as their spatial relationships with the surrounding vascular structures. This has implications for the accurate prenatal diagnosis and management of neonates with abnormal systemic venous connections.