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

Feasibility of Semiautomatic Fetal Intelligent Navigation Echocardiography for Different Fetal Spine Positions: A Matter of "Time"?

OBJECTIVES

We investigated the feasibility of a semiautomatic approach for assessments of the fetal heart (fetal intelligent navigation echocardiography [FINE]) in cases of optimal and unfavorable fetal spine positions.

METHODS

In this study, a total of 1693 spatiotemporal image correlation volumes of first-, second-, and third-trimester fetuses were evaluated by experts using the FINE approach. The data were analyzed regarding proper reconstruction of the diagnostic cardiac planes depending on the fetal spine position.

RESULTS

A total of 1531 volumes were included. The volumes were divided into 4 groups depending on the fetal spine position: 5-7 o'clock, 4 + 8 o'clock, 3 + 9 o'clock, and 2 + 10 o'clock. In total, 93.2% of the diagnostic planes were displayed properly. Between 5 and 7 o'clock, 94.9% of the diagnostic planes were displayed properly. The correct depiction rates in the other groups were 92.4% (4 + 8 o'clock; n = 538; P = 0.0027), 88.3% (3 + 9 o'clock; n = 156; P < .0001), and 87.3% (2 + 10 o'clock; n = 41; P = .0139). In total, the highest dropout rates were found in the sagittal planes: ductal arch, 13.9%; aortic arch, 10.5%; and venae cavae, 12.0%.

CONCLUSIONS

Based on our results, the FINE technique is an effective method, but its feasibility depends on the fetal position. The use of this semiautomatic work flow-based approach supports evaluation of the fetal heart in a standardized manner. Semiautomatic evaluation of the fetal heart might be useful in facilitating the detection of fetal cardiac anomalies.

Automatic Fetal Middle Sagittal Plane Detection in Ultrasound Using Generative Adversarial Network

Background and Objective: In the first trimester of pregnancy, fetal growth, and abnormalities can be assessed using the exact middle sagittal plane (MSP) of the fetus. However, the ultrasound (US) image quality and operator experience affect the accuracy. We present an automatic system that enables precise fetal MSP detection from three-dimensional (3D) US and provides an evaluation of its performance using a generative adversarial network (GAN) framework. Method: The neural network is designed as a filter and generates masks to obtain the MSP, learning the features and MSP location in 3D space. Using the proposed image analysis system, a seed point was obtained from 218 first-trimester fetal 3D US volumes using deep learning and the MSP was automatically extracted. Results: The experimental results reveal the feasibility and excellent performance of the proposed approach between the automatically and manually detected MSPs. There was no significant difference between the semi-automatic and automatic systems. Further, the inference time in the automatic system was up to two times faster than the semi-automatic approach. Conclusion: The proposed system offers precise fetal MSP measurements. Therefore, this automatic fetal MSP detection and measurement approach is anticipated to be useful clinically. The proposed system can also be applied to other relevant clinical fields in the future.

Semiautomatic Fetal Intelligent Navigation Echocardiography Has the Potential to Aid Cardiac Evaluations Even in Less Experienced Hands

OBJECTIVES

To investigate the interobserver and intraobserver variability and corresponding learning curve in a semiautomatic approach for a standardized assessment of the fetal heart (fetal intelligent navigation echocardiography [FINE]).

METHODS

A total of 30 stored spatiotemporal image correlation volume data sets of second-trimester fetuses were evaluated by 3 physicians with different levels of expertise in fetal echocardiography by using the FINE approach. Data were analyzed regarding the examination time and proper reconstruction of the diagnostic cardiac planes. The completions and numbers of correct depictions of all diagnostic planes were evaluated by a blinded expert (time t0). To determine interobserver and intraobserver variability, the volumes were reassessed after a 4-week training interval (time t1).

RESULTS

All operators were able to perform the investigation on all 30 volumes. At t0, the interobserver variability between the beginner and both the advanced (P = .0013) and expert (P < .0001) examiners was high. Focusing on intraobserver variability at t1, the beginner showed a marked improvement (P = .0087), whereas in advanced and expert hands, no further improvement regarding proper achievement of all diagnostic planes could be noticed (P > .999; P = .8383). The beginner also showed improvement in the mean investigation time (t0, 82.8 seconds; t1, 73.4 seconds; P = .0895); nevertheless, the advanced and expert examiners were faster in completing the examination (t1, advanced, 20.9 seconds; expert, 28.3 seconds; each P < .0001).

CONCLUSIONS

Based on our results, the FINE technique is a reliable and easily learned method. The use of this semiautomatic work flow-based approach supports evaluation of the fetal heart in a standardized and time-saving manner. A semiautomatic evaluation of the fetal heart might be useful in facilitating the detection of fetal cardiac anomalies.

Fetal Intelligent Navigation Echocardiography (FINE) Detects 98% of Congenital Heart Disease

OBJECTIVE

Fetal intelligent navigation echocardiography (FINE) is a novel method that automatically generates and displays 9 standard fetal echocardiographic views in normal hearts by applying intelligent navigation technology to spatiotemporal image correlation (STIC) volume data sets. The main objective was to determine the sensitivity and specificity of FINE in the prenatal detection of congenital heart disease (CHD).

METHODS

A case-control study was conducted in 50 fetuses with a broad spectrum of CHD (cases) and 100 fetuses with normal hearts (controls) in the second and third trimesters. Using 4-dimensional ultrasound with STIC technology, volume data sets were acquired. After all identifying information was removed, the data sets were randomly distributed to a different investigator for analysis using FINE. The sensitivity and specificity for the prenatal detection of CHD, as well as positive and negative likelihood ratios were determined.

RESULTS

The diagnostic performance of FINE for the prenatal detection of CHD was: sensitivity of 98% (49 of 50), specificity of 93% (93 of 100), positive likelihood ratio of 14, and negative likelihood ratio of 0.02. Among cases with confirmed CHD, the diagnosis with use of FINE completely matched the final diagnosis in 74% (37 of 50); minor discrepancies were seen in 12% (6 of 50), and major discrepancies were seen in 14% (7 of 50).

CONCLUSIONS

This is the first time the sensitivity and specificity of the FINE method in fetuses with normal hearts and CHD in the second and third trimesters has been reported. Because FINE identifies a broad spectrum of CHD with 98% sensitivity, this method could be used prenatally to screen for and diagnose CHD.

Segmentation and classification in MRI and US fetal imaging: Recent trends and future prospects

Fetal imaging is a burgeoning topic. New advancements in both magnetic resonance imaging and (3D) ultrasound currently allow doctors to diagnose fetal structural abnormalities such as those involved in twin-to-twin transfusion syndrome, gestational diabetes mellitus, pulmonary sequestration and hypoplasia, congenital heart disease, diaphragmatic hernia, ventriculomegaly, etc. Considering the continued breakthroughs in utero image analysis and (3D) reconstruction models, it is now possible to gain more insight into the ongoing development of the fetus. Best prenatal diagnosis performances rely on the conscious preparation of the clinicians in terms of fetal anatomy knowledge. Therefore, fetal imaging will likely span and increase its prevalence in the forthcoming years. This review covers state-of-the-art segmentation and classification methodologies for the whole fetus and, more specifically, the fetal brain, lungs, liver, heart and placenta in magnetic resonance imaging and (3D) ultrasound for the first time. Potential applications of the aforementioned methods into clinical settings are also inspected. Finally, improvements in existing approaches as well as most promising avenues to new areas of research are briefly outlined.

A Prospective Study of the Use of Fetal Intelligent Navigation Echocardiography (FINE) to Obtain Standard Fetal Echocardiography Views

OBJECTIVE

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

METHODS

In this prospective cohort study of patients with normal fetal hearts (19-30 gestational weeks), one or more STIC volume datasets were obtained of the apical four-chamber view. Each STIC volume successfully obtained was evaluated by STICLoop™ to determine its appropriateness before applying the FINE method. Visualization rates for standard fetal echocardiography views using diagnostic planes and/or Virtual Intelligent Sonographer Assistance (VIS-Assistance®) were calculated.

RESULTS

One or more STIC volumes (total n = 463) were obtained from 246 patients. A single STIC volume per patient was analyzed using the FINE method. In normal cases, FINE was able to generate nine fetal echocardiography views using: (1) diagnostic planes in 76-100% of the cases, (2) VIS-Assistance® in 96-100% of the cases, and (3) a combination of diagnostic planes and/or VIS-Assistance® in 96-100% of the cases.

CONCLUSION

FINE applied to STIC volumes can successfully generate nine standard fetal echocardiography views in 96-100% of cases in the 2nd and 3rd trimesters. This suggests that the technology can be used as a method of screening for congenital heart disease.

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.

New technique for assessing fetal heart growth using three-dimensional ultrasonography: description of the technique and reference curves

OBJECTIVE

To describe a new technique for assessing fetal growth using three-dimensional ultrasonography (3DUS) using the extended imaging virtual organ computer-aided analysis (XI VOCAL) software and its respective reference curves.

METHODS

We conducted a cross-sectional study on 303 normal singleton pregnancies between their 20th and 34th weeks. To assess fetal heart growth, we used the XI VOCAL software with 10 planes in which the reference lines (beginning and end) were placed at the cardiac apex, the output level of the vessels and the base above the diaphragm, respectively. To assess the correlation between distance and interval, polynomial regressions were performed with adjustments using the coefficient of determination (R(2)). To assess the inter-observer reproducibility, we used the intraclass correlation coefficient (ICC).

RESULTS

The mean distance between the apex and the base of the fetal heart ranged from 14.41 ± 1.24 mm to 26.24 ± 2.62 mm between the 20th and 34th weeks, respectively. The mean interval between the apex and the base of the fetal heart ranged from 1.56 ± 0.13 mm and 2.94 ± 0.30 mm between the 20th and 34th weeks, respectively. We observed good correlation of distance and interval with the gestational age, with R(2) = 0.73 and 0.74, respectively. We observed a good inter-observer to the interval and distance with ICC = 0.983 and 0.996, respectively.

CONCLUSION

We described a new technique for assessing fetal heart growth using 3DUS and determined reference curves for the distance and interval between the 20th and 34th weeks of pregnancy.

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.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

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.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

MRI Determination of Knee Effusion Volume: A Cadaveric Study

Background

There is currently limited literature on quantitative determination of knee effusion volume using magnetic resonance imaging (MRI).

Purpose

To describe a method of knee effusion volume determination using MRI generated models and to demonstrate accuracy of this technique.

Materials and methods

Using axial T2-weighted turbo spin echo and sagittal SPACE sequences, MRIs of three cadaver knees with multiple saline loads were obtained. Effusions models were created and effusion volumes were estimated using the Rhinoceros software. Estimated and known effusion volumes were compared using a bivariate correlation analysis.

Results

The SPACE sequence and T2WTSE estimates were highly correlated with the known volumes (R = 0.996 and 0.993 respectively, p < 0.001).

Conclusion

MRI-generated models of knee effusions provide accurate estimates of knee effusion volumes.

Clinical relevance

MRI determination of knee effusion volume may provide a useful clinical outcomes tool.

Wittstein J, Spritzer C, Garrett WE. MRI Determination of Knee Effusion Volume: A Cadaveric Study. The Duke Orthop J 2013;3(1):67-70.

A new automatic algorithm to extract craniofacial measurements from fetal three-dimensional volumes

OBJECTIVES

Three-dimensional (3D) ultrasound is useful in the prenatal evaluation of fetal craniofacial structures, particularly as it provides a multiplanar view. However, an expert must designate the area of interest and the appropriate view, making measurement of fetal structures using 3D ultrasound both time-consuming and subjective. In this study we propose an image analysis system that measures automatically and precisely the fetal craniofacial structures and evaluate its performance in the second trimester of pregnancy using a new 3D volume analysis algorithm.

METHODS

A universal facial surface template model containing the geometric shape information of a fetal craniofacial structure was constructed from a fetal phantom. Using the proposed image analysis system we fitted this stored template model using a model deformation approach to individual fetal 3D facial volumes from 11 mid-trimester fetuses, and extracted automatically the following standard measurements: biparietal diameter (BPD), occipitofrontal diameter (OFD), interorbital diameter (IOD), bilateral orbital diameter (BOD) and distance between vertex and nasion (VN). The same five parameters were measured manually by an expert and the results compared.

RESULTS

Comparison of the algorithm-based automatic measurements with manual measurements made by an expert gave correlation coefficients of 0.99 for BPD, 0.98 for OFD, 0.80 for BOD, 0.83 for IOD and 0.99 for VN. There were no significant differences between automatic and manual measurements.

CONCLUSION

Our proposed system measures precisely the fetal craniofacial structures using 3D ultrasound, making it potentially useful for clinical service. This system could also be applied to other clinical fields in future testing.

Comparison of Doppler-based and three-dimensional methods for fetal cardiac output measurement

OBJECTIVE

Fetal cardiac output is conventionally measured using two-dimensional (2D) and Doppler ultrasound (Doppler). New methods based on 3D measurements of ventricular size in systole and diastole have been proposed. Our aim was to validate these tools against the conventional Doppler-based methods.

METHODS

Fetal combined cardiac output was prospectively measured at 16, 20, and 24 weeks of gestation in 15 uncomplicated pregnancies using Doppler and three different 3D algorithms [virtual organ computer-aided analysis (VOCAL), sonographic automatic volume calculation (SonoAVC), and inversion mode]. We determined the inter- and intraobserver variability of the 3D techniques and assessed the correlation between Doppler and 3D.

RESULTS

The 3D techniques showed adequate inter- and intraobserver reproducibility (intraclass correlation coefficient 0.69-0.98), with the best reproducibility for SonoAVC and inversion mode. Bland-Altman analysis revealed low bias and relatively good correlations when comparing the 3D methods among each other, albeit with wide 95% confidence intervals. Doppler measurement of fetal weight-adjusted combined cardiac output (349.0 ml·min⁻¹·kg⁻¹) yielded significantly higher results than 3D CO measurements (177.2, 160.7, and 174.0 ml·min⁻¹·kg⁻¹ for VOCAL, SonoAVC, and inversion mode, respectively; p < 0.0001) and correlated poorly with the 3D methods.

CONCLUSIONS

Although 3D volume-based cardiac output measurements are reproducible, results obtained with different methods are not interchangeable. SonoAVC and inversion have the highest intra- and interobserver reproducibility. Results of cardiac output measurement by 3D and Doppler cannot be interchanged.

2D/3D fetal cardiac dataset segmentation using a deformable model

PURPOSE

To segment the fetal heart in order to facilitate the 3D assessment of the cardiac function and structure.

METHODS

Ultrasound acquisition typically results in drop-out artifacts of the chamber walls. The authors outline a level set deformable model to automatically delineate the small fetal cardiac chambers. The level set is penalized from growing into an adjacent cardiac compartment using a novel collision detection term. The region based model allows simultaneous segmentation of all four cardiac chambers from a user defined seed point placed in each chamber.

RESULTS

The segmented boundaries are automatically penalized from intersecting at walls with signal dropout. Root mean square errors of the perpendicular distances between the algorithm's delineation and manual tracings are within 2 mm which is less than 10% of the length of a typical fetal heart. The ejection fractions were determined from the 3D datasets. We validate the algorithm using a physical phantom and obtain volumes that are comparable to those from physically determined means. The algorithm segments volumes with an error of within 13% as determined using a physical phantom.

CONCLUSIONS

Our original work in fetal cardiac segmentation compares automatic and manual tracings to a physical phantom and also measures inter observer variation.

Role of four-dimensional ultrasound (spatiotemporal image correlation and sonography-based automated volume count) in prenatal assessment of atrial morphology in cardiosplenic syndromes

OBJECTIVE

To assess the diagnostic role of four-dimensional ultrasound using spatiotemporal image correlation and Sonography-based Automated Volume Count (STIC-SonoAVC) in the identification of the morphology of the atrial appendages in cases with cardiosplenic syndrome.

METHODS

This was a retrospective investigation of 22 fetuses with cardiosplenic syndromes seen at our institution over a 5-year period from January 2004. As control groups, 10 normal fetuses, five cases with a non-isomeric atrioventricular septal defect and five cases with other congenital heart diseases were also analyzed. For all fetuses, one or more cardiac volume datasets were available for offline analysis. Two-dimensional and four-dimensional echocardiography was carried out in all cases at the time of diagnosis using high quality three-dimensional equipment. Dedicated software was used to assess chamber morphology using the SonoAVC technique, which allows the creation of casts of hollow structures. Two different operators used the software. The first performed all steps up to positioning of the region of interest box. The second operator, who was blinded to clinical information, then rendered the cardiac chambers using the SonoAVC technique. This operator then used the rendered image to subjectively assess atrial morphology.

RESULTS

Suitable rendered images of the cardiac chambers could be produced in 40/42 fetuses. In two cases of left atrial isomerism, advanced (34 weeks) and early (13 weeks) gestational age made it impossible to obtain adequate rendered images. In the remaining 40 cases (13 cases of left atrial isomerism, seven cases of right atrial isomerism, five cases of non-isomeric atrioventricular septal defect, five cases of other congenital heart diseases and 10 normal fetuses), atrial morphology was correctly identified by evaluation of the rendered images.

CONCLUSION

Four-dimensional ultrasound with SonoAVC rendering allows correct identification of the morphology of atrial appendages in all cases of cardiosplenic syndromes in which an adequate cardiac volume dataset can be obtained for analysis.

Techniques for assessing cardiac output and fetal cardiac function

Fetal echocardiography was initially used to diagnose structural heart disease, but recent interest has focused on functional assessment. Effects of extracardiac conditions on the cardiac function such as volume overload (in the recipient in twin-twin transfusion syndrome), a hyperdynamic circulation (arterio-venous malformation), cardiac compression (diaphragmatic hernia, lung tumours) and increased placental resistance (intrauterine growth restriction and placental insufficiency) can be studied by ultrasound and may guide decisions for intervention or delivery. A variety of functional tests can be used, but there is no single clinical standard. For some specific conditions, however, certain tests have shown diagnostic value.

Role of sonographic automatic volume calculation in measuring fetal cardiac ventricular volumes using 4-dimensional sonography: comparison with virtual organ computer-aided analysis

OBJECTIVE

The purpose of this study was to compare the agreement and reliability of virtual organ computer-aided analysis (VOCAL) and sonographic automatic volume calculation (sonoAVC) for measurements of ventricular volume from fetal heart data sets acquired by 4-dimensional sonography with spatiotemporal image correlation (STIC).

METHODS

We studied 45 volumes from fetuses with normal (n = 30) and abnormal (n = 15) hearts. Spatiotemporal image correlation data sets were frozen in end systole and end diastole, and ventricular volumes were measured with VOCAL and sonoAVC. The stroke volume was calculated from these measurements. Reliability and agreement of the two techniques were evaluated with intraclass correlation coefficients (ICCs), and proportionate Bland-Altman plots were constructed. The time necessary to complete the measurements with either technique was compared. Intraobserver and interobserver agreement of measurements was calculated.

RESULTS

All data sets could be measured with both techniques. A high degree of reliability was observed between VOCAL and sonoAVC (left ventricular stroke volume ICC, 0.978; 95% confidence interval [CI], 0.957-0.989; right ventricular stroke volume ICC, 0.985; 95% CI, 0.972-0.992). The time necessary to measure the stroke volume was significantly shorter with sonoAVC (2.8 versus 11.7 minutes; P < .0001) than with VOCAL. Bland-Altman tests showed no clinically significant mean percent differences between stroke volume measurements obtained from each ventricle by the same observer or by 2 independent observers using either VOCAL or sonoAVC.

CONCLUSIONS

There was good agreement between cardiac volumes measured with VOCAL and sonoAVC. Sonographic automatic volume calculation represents a rapid technique for estimating fetal stroke volume and promises to become the method of choice.

Does running cause metatarsophalangeal joint effusions? A comparison of synovial fluid volumes on MRI in athletes before and after running

OBJECTIVE

The metatarsophalangeal joints (MTPJ) are the only joints that bear weight directly through synovium. The purpose of this study was to determine whether there is an association between synovial stresses during running and increases in volume of joint fluid.

MATERIALS AND METHODS

This was a prospective case controlled study (nine healthy athlete volunteers acting as own controls). High-resolution coronal 3D T2W magnetic resonance imaging of the MTPJs were obtained following 24 h rest and after a 30-min run. The volume of joint fluid in each MTPJ (n = 90) was measured by two independent observers using an automated propagating segmentation tool.

RESULTS

The median volume of synovial fluid in the MTPJs at rest was 0.018 ml (inter-quartile range (IQ) range 0.005-0.04) and after running 0.019 ml (IQ range 0.005-0.04, p = 0.34, 99% confidence interval (CI), 0.330.35). The volume of fluid in the MTPJs of the great toes was substantially larger than other toes (0.152 ml at rest, 0.154 ml after exercise, p = 0.903). Median volumes decrease from second to fifth MTPJs (0.032-0.007 ml at rest and 0.035-0.004 ml after exercise). Subset analysis for each toe revealed no significant difference in volumes before and after running (p = 0.39 to p = 0.9). The inter-rater reliability for observer measurements was good with an intra-class correlation of 0.70 (95% CI, 0.60 to 0.78).

CONCLUSION

It appears to be normal to find synovial fluid, particularly in the MTPJs of the great toes, of athletes at rest and after running. There does not appear to be an association between moderate distance running and an increase in the volume of synovial fluid.