Fetal Cardiac Imaging Research Articles

Improved cardiac motion self-gating

Background Cardiac motion self-gating is a technique where MRI signal is used to derive motion triggers instead of ECG, which might be problematic in high B0 field or cases where ECG is not accessible (e.g. fetal cardiac imaging). However, the performance of existing cardiac self-gating approaches have not yet enabled clinical utility. We propose and evaluate here a novel cardiac self-gating strategy that potentially improves the trigger detection accuracy and reliability.

Automated Screening of Fetal Heart Chambers from 2-D Ultrasound Cine-Loop Sequences

Fetal cardiac ultrasonic imaging technique has become increasingly popular in the recent years for the detection of fetal congenital abnormalities at an early stage. Due to the low signal-to-noise ratio of the ultrasound imaging, the automatic detection methods should incorporate suitable preprocessing filtering techniques to enhance the segmentation techniques efficiently. This paper suggests the application of median and morphological filtering operation for removing speckle noise. Then the four heart chambers are segmented independently based on the shape priors. The amorphous snake’s helps in identifying the contours of the chamber edges individually based on shape pattern. Experimental study involves the ultrasound cine-loop sequences of the apical four chamber view of fetal heart with a constant frame rate of 25 frames per second (fps) with varying duration of 10-30s encompassing a range of 20-40 complete cardiac cycles. The simulation result confirms the suitability of proposed scheme for automated screening of fetal heart chambers.

Investigation into the Fusion of Multiple 4-D Fetal Echocardiography Images to Improve Image Quality

Recent advances in four-dimensional (4-D) ultrasound enable the acquisition and visualisation of the entire fetal heart. However, getting consistent, shadow free, data remains problematic due to the uncontrollable nature of fetal orientation. This article presents the first investigation into the utility of image fusion to improve the quality of volumetric fetal cardiac imaging. Multiple volume scans are registered using a semiautomatic approach and five fusion methods are assessed for their ability to remove artefacts and improve image quality. Image quality is assessed in terms of signal-to-noise ratio, contrast and contrast-to-noise ratio. Qualitative results are presented for the ability to remove artefacts. The fusion methods assessed were found to be divided into those that reduce noise and those that increase contrast. The effect of fusion on left ventricle segmentation using commercial state-of-the-art software is also considered. The use of image fusion is shown to reduce the variability of volume estimates by about 50% relative to measurement on a single scan. (E-mail: gooding@robots.ox.ac.uk)

348: Fetal cardiac imaging in early gestation: what can be seen and when?

348: Fetal cardiac imaging in early gestation: what can be seen and when?

P24.01: Limiting factors for performance of the automated sonography in fetal cardiac imaging in the second trimester of pregnancy

P24.01: Limiting factors for performance of the automated sonography in fetal cardiac imaging in the second trimester of pregnancy

OC14.05: Fetal cardiac MR imaging with cardiac triggering in the sheep fetus: preliminary results

thickness = 5 mm, FOV 240 mm × 240 mm and a matrix of 128 × 128. The voxel size was 1.9 mm × 1.9 mm × 5.0 mm. Two b-values (0 and 1000) were chosen along three orthogonal directions. Apparent diffusion coefficient (ADC) maps were created using assigned b-values. Offline software was used to manually trace ADC maps of fetal lung (Osirix). Simple linear regression was performed with Pearson correlation coefficient. Interand intraexaminer bias and 95% limits of agreement (LOA) were determined using Bland–Altman plots. Results: Forty-seven scans were performed at 26.8 ± 4.6 weeks (1 SD). The median coefficient of variation for ADC was 5.6% [IQR 4.0-8.1%]. No differences in ADC values were found between either lung. Hence, subsequent analysis was based on manual tracing of the largest arbitrary image slice of the right lung. ADC values were not significantly correlated with either total lung volume (r2 = 0.0001, p = 0.94, n.s) or menstrual age (r2 = 0.003, p = 0.70, n.s). The mean ADC value was 1.75 [95% CI, 1.63-1.86]. Intra-examiner bias was −0.15 ± 2.3 [95% limits of agreement, −4.7 to +4.4]. Inter-examiner bias was 2.2 ± 3.5 [95% limit of agreement, −4.7 to +9.1]. Conclusion: ADC measurements from the fetal lung are reproducible between blinded examiners and are independent of menstrual age, as well as lung volume.

OC18.04: Prospective evaluation of automated sonography in comprehensive fetal cardiac imaging in the second trimester of pregnancy

OC18.04: Prospective evaluation of automated sonography in comprehensive fetal cardiac imaging in the second trimester of pregnancy

Utility of Fetal Echocardiography After Normal Cardiac Imaging Findings on Detailed Fetal Anatomic Ultrasonography

The purpose of this study was to assess the utility of fetal echocardiography (FE) after normal fetal cardiac imaging findings during detailed fetal anatomic ultrasonography (FAU). We conducted a retrospective cohort review of obstetric ultrasonographic studies from November 2001 through July 2005. We identified women with a singleton gestation with increased risk for congenital heart disease who received FAU performed by a maternal-fetal medicine specialist at 16 to 20 weeks' gestation with subsequent FE. These records were compared with newborn outcomes. Of 789 pregnancies that had FAU and FE, 481 had satisfactory cardiac imaging. Of those, only 1 fetus had abnormal FE findings. After delivery, 4 of the 480 neonates with normal FAU and FE findings had a diagnosis of a heart defect. Fetal echocardiography does not substantially increase the detection rate of major cardiac anomalies after normal findings on detailed FAU performed by a maternal-fetal medicine specialist.

Quality of 2- and 3-Dimensional Fast Acquisition Fetal Cardiac Imaging at 18 to 22 Weeks

The purpose of this study was to evaluate the frequency with which 6 different fetal cardiac views taken during a fetal ultrasound examination at 18 to 22 weeks' gestation can be obtained satisfactorily for cardiac anomaly screening using either a 2-dimensional (2D) static or 3-dimensional (3D) fast acquisition technique. A prospective study of 100 low-risk women undergoing an anatomic survey was performed. Standard static 2D and 3D fast acquisition volumes were obtained on all patients. The 2D and 3D images were assigned, in a random order, to be independently graded by 3 reviewers. The degree of inter-reviewer agreement was assessed through the use of the Cohen kappa statistic. The factors contributing to satisfactory imaging were evaluated by random effects logistic regression. A significant proportion of both 2D and 3D images were judged unsatisfactory for screening purposes. However, 2D images were significantly more likely, for all cardiac views, to be judged satisfactory (P < .05). The odds ratios for the 2D technique's being more likely than the 3D technique to provide images satisfactory for screening were 2.6 for the 4-chamber view, 2.4 for the right ventricular outflow tract, 4 for the left ventricular outflow tract, 3.2 for the 3-vessel view, 8.6 for the aortic arch, and 2.2 for the ductal arch. In this prospective study, static 2D imaging was significantly more likely than fast acquisition 2D imaging to yield cardiac views of high enough quality to satisfactorily screen for anomalies.

Fetal mid-muscular ventricular septal defect: Role of fetal cardio-vascular evaluation with magnetic resonance (MR) imaging and MR-angiography

We report our experience with fetal cardiac MR imaging and fetal MR-angiography in a 35 + 5-week fetus with a ventricular septal defect (VSD). Case: A fetus with an abnormal four-chamber view at obstetric US and a VSD of the medio-muscular portion of the ventricular septum at echocardiography underwent MRI to assess possible associated anomalies. Gradient Echo (GE) sequences with steady-state free precession (TrueFISP) and cine-MR sequences demonstrated a 4 mm VSD involving the medio-muscular portion of the septum in a morphologically and volumetrically normal fetal heart with a correct origin of the great arteries. T1-weighted 3D spoiled sequences permitted to obtain angiographic images and MIP reconstructions that proved a normal size and position of the aorta disconfirming a suspected coartaction of the aorta. Conventional T2-weighted sequences excluded the presence of extracardiac abnormalities. A postnatal echocardiography, considered as standard of reference confirmed the VSD in an otherwise normal male newborn.

A Primer for Fetal Cardiac 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.

OC170: Can four‐dimensional ultrasound with spatiotemporal image correlation be used in the measurement of fetal aortic and pulmonary valve sizes in normal and abnormal hearts?

real-time 3D/4D imaging, which has achieved adequate resolution for measurement of fetal ventricular volumes. Methods: We studied the fetal hearts in 30 pregnant women (range, 21–34 years) with STIC (GE Kretz, Voluson 730, Vocal) and 37 fetuses (16–36 weeks’ gestation) using a 3-MHz (x3-1/iE33, Philips Medical Systems, QLab/3DQAdvanced) or a new 7-MHz (x7/iE33, Philips) 2D matrix array transducer. Full 4D volumes were acquired, some with an internal HR trigger in the system. End-diastolic and end-systolic RV and LV volumes and ejection fractions were measured for both ventricles. Results: Measurements of one or both fetal cardiac ventricles could be successfully obtained in all STIC cases and in 27 of the 37 fetuses analyzed using the matrix array system. For the latter, a total of 115 ‘full cardiac volumes’ (between one and 11 per fetus) were analyzed. Between 20 and 36 weeks’ gestation fetal ventricular volumes in ED and ES increased from 0.4 mL to 4 mL and 0.2 mL to 1.7 mL for the RV, and from 0.4 mL to 3.3 mL and 0.3 mL to 1.7 mL for the LV. Conclusions: Similar results for chamber growth and function have been observed in our study using the two 4D methods for fetal cardiac imaging. It is likely that these measurements are definitive and universal.

Does Spatiotemporal Image Correlation Enhance the Diagnostic Usefulness of 3D and 4D Fetal Cardiac Imaging? A Literature Review

Does Spatiotemporal Image Correlation Enhance the Diagnostic Usefulness of 3D and 4D Fetal Cardiac Imaging? A Literature Review

OP04.34: Assessment of the fetal myocardial performance by tissue Doppler imaging

The myocardial performance index (MPI) determined by conventional pulsed Doppler method is a simple non-invasive measurement for assessing global ventricular function. Recently the MPI has shown promise in the analysis of ventricular function in fetuses, children and adults with various heart diseases. This index can also be obtained by PW-Tissue Doppler Imaging (PW-TDI). Color Tissue Doppler Imaging (C-TDI) is a new tool in adult cardiology. It represents a novel approach to fetal cardiac imaging. Until now there is no experience with C-TDI for the assessment of a fetal MPI. In the present study, we analysed 180 data files of 20 normal fetuses (20.0–25.0 week of gestation). After a echocardiographic examination, high-frame rate (> 100/sec) TDI data of an apical four chamber view was recorded with a Toshiba Aplio 80 research ultrasound system. At least 3 consecutive fetal cardiac cycles were stored digitally. Velocities were measured offline with TDIQ-software by placement of 8 ROI (RA; LA; RV, LV and Septum annular; RV, LV and Septum basal). A fetal heart cycle was identified and measured reproducible. The anunular and ventricular measurements allowed the evaluation of the following systolic and diastolic velocity parameters: IVC; systole (ejection); IVR; E′- and A′-wave. Based on this data the calculation of the MPI and other current performance parameters, e. g. IVA and E/A ratio, was possible by the use of C-TDI. The calculated fetal MPI values correspond to published data of PW and PW-TDI studies. Measurements of the fetal MPI by C-TDI is easy to obtain. For the first time C-TDI allows the comparison of biventricular performance parameters in the same fetal cardiac cycle. Therefore it is a promising new tool for the assessment of fetal heart function.

Current applications of fetal cardiac imaging technology

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. 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. 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.

A Review of Fetal Circulation and the Segmental Approach in Fetal Echocardiography

The incidence of congenital heart disease is generally estimated at 8 in 1000 live births. Fifty percent of these neonates will have “minor” defects—easily corrected with some intervention. The remainder will account for 30% of perinatal deaths and nearly 50% of lethal malformations in childhood. The purpose of this review is to outline essential guidelines for a thorough fetal echocardiogram and how it differs from the fetal cardiac imaging included as part of an obstetric sonographic examination. Specific values for both the anatomic and blood flow velocity measurements recommended are typically related to gestational age and method of acquisition. Multiple references exist in the literature that define these values.

Prenatal screening for congenital heart disease using real‐time three‐dimensional echocardiography and a novel ‘sweep volume’ acquisition technique

Conventional prenatal screening for congenital heart disease (CHD) involves a time-consuming and highly operator-dependent acquisition of the four-chamber view and outflow tracts. By acquiring the entire fetal heart instantaneously as a single volume, real-time three-dimensional echocardiography (RT3DE) may facilitate fetal cardiac screening. Four reviewers, each experienced with fetal cardiac imaging, blindly and independently evaluated a single cardiac volume from each of 18 fetuses (11 normal, seven with CHD). Two-dimensional echocardiography served as the gold standard. Three-dimensional evaluation of each fetus included a series of volume acquisitions lasting 2-6 s each. A 'sweep volume' technique was developed to fit larger hearts into a single non-gated volume. RT3DE had a high sensitivity for detecting CHD (93%), with only a single case being missed by two observers. Specificity for CHD was low (45%), with a high rate of 'cannot determine' responses and false positive artifacts. These preliminary results suggest that RT3DE has the potential to function as a screening tool for fetal heart disease. However, artifacts must be recognized and minimized, resolution must improve, and substantial training will be necessary prior to widespread clinical use.

Flow-gated phase-contrast MRI using radial acquisitions.

Phase-contrast (PC) MRI is a noninvasive method for imaging blood and tissue velocity. PC experiments are typically segmented into many cardiac cycles in order to obtain sufficient spatial and temporal resolution, and thus require a gating signal to properly combine the data from multiple cardiac cycles. Although the surface electrode ECG is the gating waveform of choice for cardiovascular MRI, alternative gating methods are required for fetal cardiac imaging (due to the unavailability of fetal ECG signals) and for cases of ECG contamination via the strong magnetic fields within the MR scanner. This study demonstrates the feasibility of using imaging data from flow-encoded MRI experiments to derive times for cardiac gating. An undersampled radial k-space acquisition method is used to measure an image-derived flow-gating waveform in real-time, from which the gating times are derived. These gating times are used to reconstruct a conventional gated-segmented image series by combining the real-time data from multiple heartbeats. Flow-gated PC experiments were performed on five normal volunteers with slice prescriptions in four anatomic regions. The standard deviation (SD) of the difference between the flow-gating and ECG gating times ranged from 5 ms to 12 ms.

Advances in fetal cardiac imaging.

During the past 25 years, two-dimensional imaging of the fetal heart has evolved into a sophisticated and widely practiced clinical tool, but most heart disease still goes undetected until sometime after birth, despite routine fetal ultrasound evaluations. Over the next 25 years, tremendous advances in fetal cardiac imaging, including three-dimensional imaging, promise to revolutionize both the prenatal detection and diagnosis of congenital heart disease. Image resolution continues to improve year after year, allowing earlier (10-15 week) visualization of the fetal heart, as well as the detection of subtle valvar abnormalities that may progress to serious forms of ventricular hypoplasia at term. However, fetal cardiac imaging remains constrained by limited sonographic windows. To improve the prenatal detection of congenital heart disease, outflow tracts are increasingly included along with the routine screening four-chamber view. However, while the four-chamber view resides within a single plane, lending itself to tomographic evaluation with two-dimensional ultrasound, the outflow tracts (and most forms of congenital heart disease) do not reside within a single plane. For these and other reasons, three-dimensional imaging of the fetal heart ultimately may improve the detection of outflow tract abnormalities, and facilitate comprehension of complex forms of congenital heart disease. Finally, other imaging modalities, including but not limited to Doppler tissue imaging and magnetic resonance imaging, continue to evolve and to complement two- and three-dimensional sonographic imaging of the fetal heart. As a result of these ongoing advances in the prenatal detection and assessment of congenital heart disease, these are exciting and glorious times for the field of fetal cardiac imaging.

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

Random fetal motion, rapid fetal heart rates, and cumbersome processing algorithms have limited reconstructive approaches to 3-dimensional fetal cardiac imaging. Given the recent development of real-time, instantaneous volume-rendered sonographic displays of volume data, we sought to apply this technology to fetal cardiac imaging. We obtained 1 to 6 volume data sets on each of 30 fetal hearts referred for formal fetal echocardiography. Each volume data set was acquired over 2 to 8 seconds and stored on the system's hard drive. Rendered images were subsequently processed to optimize translucency, smoothing, and orientation and cropped to reveal "surgeon's eye views" of clinically relevant anatomic structures. Qualitative comparison was made with conventional fetal echocardiography for each subject. Volume-rendered displays identified all major abnormalities but failed to identify small ventricular septal defects in 2 patients. Important planes and views not visualized during the actual scans were generated with minimal processing of rendered image displays. Volume-rendered displays tended to have slightly inferior image quality compared with conventional 2-dimensional images. Real-time 3-dimensional echocardiography with instantaneous volume-rendered displays of the fetal heart represents a new approach to fetal cardiac imaging with tremendous clinical potential.