Novel Flow Quantification of the Carotid Bulb and the Common Carotid Artery with Vector Flow Ultrasound

Abnormal blood flow is usually assessed using spectral Doppler estimation of the peak systolic velocity. The technique, however, only estimates the axial velocity component, and therefore the complexity of blood flow remains hidden in conventional ultrasound examinations. With the vector ultrasound technique transverse oscillation the blood velocities of both the axial and the transverse directions are obtained and the complexity of blood flow can be visualized. The aim of the study was to determine the technical performance and interpretation of vector concentration as a tool for estimation of flow complexity. A secondary aim was to establish accuracy parameters to detect flow changes/patterns in the common carotid artery (CCA) and the carotid bulb (CB). The right carotid bifurcation including the CCA and CB of eight healthy volunteers were scanned in a longitudinal plane with vector flow ultrasound (US) using a commercial vector flow ultrasound scanner (ProFocus, BK Medical, Denmark) with a linear 5 MHz transducer transverse oscillation vector flow software. CCA and CB areas were marked in one cardiac cycle from each volunteer. The complex flow was assessed by medical expert evaluation and by vector concentration calculation. A vortex with complex flow was found in all carotid bulbs, whereas the CCA had mainly laminar flow. The medical experts evaluated the flow to be mainly laminar in the CCA (0.82 ± 0.14) and mainly complex (0.23 ± 0.22) in the CB. Likewise, the estimated vector concentrations in CCA (0.96 ± 0.16) indicated mainly laminar flow and in CB (0.83 ± 0.07) indicated mainly turbulence. Both methods were thus able to clearly distinguish the flow patterns of CCA and CB in systole. Vector concentration from angle-independent vector velocity estimates is a quantitative index, which is simple to calculate and can differentiate between laminar and complex flow.     

Quantification of Ultrasound Correlation‐Based Flow Velocity Mapping and Edge Velocity Gradient Measurement

This study investigated the use of ultrasound speckle decorrelation‐ and correlation‐based lateral speckle‐tracking methods for transverse and longitudinal blood velocity profile measurement, respectively. By studying the blood velocity gradient at the vessel wall, vascular wall shear stress, which is important in vascular physiology as well as the pathophysiologic mechanisms of vascular diseases, can be obtained. Decorrelation‐based blood velocity profile measurement transverse to the flow direction is a novel approach, which provides advantages for vascular wall shear stress measurement over longitudinal blood velocity measurement methods. Blood flow velocity profiles are obtained from measurements of frame‐to‐frame decorrelation. In this research, both decorrelation and lateral speckle‐tracking flow estimation methods were compared with Poiseuille theory over physiologic flows ranging from 50 to 1000 mm/s. The decorrelation flow velocity measurement method demonstrated more accurate prediction of the flow velocity gradient at the wall edge than the correlation‐based lateral speckle‐tracking method. The novelty of this study is that speckle decorrelation‐based flow velocity measurements determine the blood velocity across a vessel. In addition, speckle decor‐relation‐based flow velocity measurements have higher axial spatial resolution than Doppler ultrasound measurements to enable more accurate measurement of blood velocity near a vessel wall and determine the physiologically important wall shear.     

Jugular Venous Flow Quantification Using Doppler Sonography

A consensus on venous flow quantification using echo spectral Doppler sonography is lacking. Doppler sonography data from 83 healthy individuals were examined using manually traced transverse cross-sectional area and diameter-derived cross-sectional area obtained in longitudinal view measurements of the internal jugular vein. Time-averaged velocity over a 4-s interval was obtained in the longitudinal plane using manual tracing of the waveform. Manual and computer-generated blood flow volume calculations were also obtained for the common carotid artery, for accuracy purposes. No differences were detected between semi-automated and manual blood flow volume calculations for the common carotid artery. The manual calculation method resulted in almost twofold larger venous internal jugular vein flow measurements compared with the semi-automated method. Doppler sonography equipment does not provide accurate automated calculation of venous size and blood flow. Until further technological development occurs, manual calculation of venous blood flow is warranted.     

Measurement of Volumetric Flow

Objective. The purpose of this study was to evaluate a 3‐dimensional (3D) sonographic method for the measurement of volumetric flow under conditions of known flow rates and Doppler angles. Methods. A GE/Kretz Voluson 730 system (GE Healthcare, Milwaukee, WI) and RAB2‐5 probe were used to acquire 3D Doppler measurements in a custom flow phantom. Blood‐mimicking fluid circulated by a computer‐controlled pump provided a range of flow velocities (2–15 mL/s). A 6‐axis positioning system maneuvered the ultrasound probe through a range of angles (40°–70° and 110°–140°) with respect to the tube (orthogonal to the tube being 90°). Volume data sets were obtained spanning 29° lateral and 20° elevational angles encompassing the flow tube in a scanning time of less than 10 seconds. Power Doppler data were used to correct for partial volume effects. Results. Using a single angle (110°) with respect to the flow tube, measured and actual volume flow rates were within the 95% confidence interval over the full range of flow rates. At flow rates of 5 and 10 mL/s, the measured volume flow rates were all within ±15% of actual values for the range of angles tested and also stayed within the 95% confidence interval. Conclusions. Direct comparisons of volume flow rates estimated with 3D sonography and known flow rates showed that the method has good accuracy. Subsequent comparisons under pulsatile and in vivo conditions will be needed to verify this performance for clinical applications.     

多普勒超声在血流量测定中的理论问题与技术问题

分析了多普勒超声在血流量测定中的若干重要问题。从理论上分析存在渡越时间增宽效应，空间最大频移与空间平均频移，血管因素，血流流速剖面等各种问题；在技术方法上有流速剖面法，均匀照射法及流速剖面假定法等。提出了用多普勒超声法研究血流量的基本概念及正确途径。多普勒超声血流量的研究既诱人亦存在许多复杂性，目前尚不成熟，需进一步深入研究。     

Current status of 3D/4D volume ultrasound of the breast

3D/4D volume ultrasound is an established method that offers various options for analyzing and presenting ultrasound volume data. The following imaging techniques are based on automatically acquired ultrasound volumes. The multiplanar view is the typical mode of 3D ultrasound data presentation. The niche mode view is a cut open view of the volume data set. The surface mode is a rendering technique that represents the data within a volume of interest (VOI) with different slice thicknesses (typically 1-4 mm) with a contrast-enhanced surface algorithm. Related to the diagnostic target, the transparency mode helps to present echopoor or echorich structures and their spatial relationships within the ultrasound volume. Glass body rendering is a special type of transparency mode that makes the grayscale data transparent and shows the color flow data in a surface render mode. The inversion mode offers a three-dimensional surface presentation of echopoor lesions. Volume Contrast Imaging (VCI) works with static 3D volume data and is able to be used with 4D for dynamic scanning. Volume calculation of a lesion and virtual computer-assisted organ analysis of the same lesion is performed with VoCal software. Tomographic Ultrasound Imaging (TUI) is the perfect tool to document static 3D ultrasound volumes. 3D/4D volume ultrasound of the breast provides diagnostic information of the coronal plane. In this plane benign lesions show the compression pattern sign, while malignant lesions show the retraction pattern or star pattern sign. The indeterminate pattern of a lesion combines signs of compression and retraction or star pattern in the coronal plane. Glass body rendering in combination with Power-Doppler, Color-Doppler or High-Definition Flow Imaging presents the intra- and peritumoral three-dimensional vascular architecture. 3D targeting shows correct or incorrect needle placement in all three planes after 2D or 4D needle guidance. In conclusion, it is safe to say that 3D/4D volume ultrasound of the breast is technically advanced and suitable for daily diagnostic and interventional breast work in addition to routinely used 2D sonography.     

In Vivo Lateral Blood Flow Velocity Measurement Using Speckle Size Estimation

In previous studies, we proposed blood measurement using speckle size estimation, which estimates the lateral component of blood flow within a single image frame based on the observation that the speckle pattern corresponding to blood reflectors (typically red blood cells) stretches (i.e., is “smeared”) if blood flow is in the same direction as the electronically controlled transducer line selection in a 2-D image. In this observational study, the clinical viability of ultrasound blood flow velocity measurement using speckle size estimation was investigated and compared with that of conventional spectral Doppler of carotid artery blood flow data collected from human patients in vivo. Ten patients (six male, four female) were recruited. Right carotid artery blood flow data were collected in an interleaved fashion (alternating Doppler and B-mode A-lines) with an Antares Ultrasound Imaging System and transferred to a PC via the Axius Ultrasound Research Interface. The scanning velocity was 77 cm/s, and a 4-s interval of flow data were collected from each subject to cover three to five complete cardiac cycles. Conventional spectral Doppler data were collected simultaneously to compare with estimates made by speckle size estimation. The results indicate that the peak systolic velocities measured with the two methods are comparable (within ±10%) if the scan velocity is greater than or equal to the flow velocity. When scan velocity is slower than peak systolic velocity, the speckle stretch method asymptotes to the scan velocity. Thus, the speckle stretch method is able to accurately measure pure lateral flow, which conventional Doppler cannot do. In addition, an initial comparison of the speckle size estimation and color Doppler methods with respect to computational complexity and data acquisition time indicated potential time savings in blood flow velocity estimation using speckle size estimation. Further studies are needed for calculation of the speckle stretch method across a field of view and combination with an appropriate axial flow estimator.     

Bedside Cerebral Blood Flow Quantification in Neonates

Measurement of blood flow to the brain in neonates would be a very valuable addition to the medical diagnostic armamentarium. Such conditions such as assessment of closure of a patent ductus arteriosus (PDA) would greatly benefit from such an evaluation. However, measurement of cerebral blood flow in a clinical setting has proven very difficult and, as such, is rarely employed. Present techniques are often cumbersome, difficult to perform and potentially dangerous for very low birth weight (VLBW) infants. We have been developing an ultrasound blood volume flow technique that could be routinely used to assess blood flow to the brain in neonates. By scanning through the anterior fontanelles of 10 normal, full-term newborn infants, we were able to estimate total brain blood flows that closely match those published in the literature using much more invasive and technically demanding methods. Our method is safe, easy to do, does not require contrast agents and can be performed in the baby's incubator. The method has the potential for monitoring and assessing blood flows to the brain and could be used to routinely assess cerebral blood flow in many different clinical conditions.     

Color Doppler examination of the outflow tracts of the fetal heart: a technique for identification of cardiovascular malformations.

The objective was to describe a technique using color Doppler to identify the outflow tracts of the fetal heart by directing the ultrasound transversely through the fetal chest. One hundred second- and third-trimester control fetuses were examined with real-time and color Doppler ultrasound. The ultrasound beam was directed cephalad, in the same transverse plane used to image the four-chamber view, and the outflow tracts were examined. Four fetuses with abnormal cardiovascular anatomy were examined using the above approach, to study the anatomical relationships of the outflow tracts identified with color Doppler ultrasound in normal fetuses.When the ultrasound beam was directed immediately cephalad to the four-chamber view, the aorta was identified as it exited the left ventricle. Further movement of the ultrasound beam cephalad identified the following vessels in a single plane: the main pulmonary artery perpendicular to the ascending aorta; the left pulmonary artery branching from the main pulmonary artery; the full length of the ductus arteriosus; and the transverse arch of the aorta. The ascending aorta, main pulmonary artery, ductus arteriosus and transverse aortic arch were identified in 100% of fetuses. Four fetuses with abnormalities of the outflow tracts (aortic stenosis, aortic regurgitation, pulmonary stenosis and premature constriction of the ductus arteriosus) were imaged using this approach in which pathology was readily identified.This technique enables rapid identification of the outflow tracts in second- and third-trimester fetuses using color Doppler and accurately identifies abnormalities of these vessels.     

Common Carotid Artery Flow Measured by 3-D Ultrasonic Vector Flow Imaging and Validated with Magnetic Resonance Imaging

Ultrasound (US) examination of the common carotid artery was compared with a through-plane magnetic resonance imaging (MRI) sequence to validate a recently proposed technique for 3-D US vector flow imaging. Data from the first volunteer examined were used as the training set, before volume flow and peak velocities were calculated for the remaining eight volunteers. Peak systolic velocities (PSVs) and volume flow obtained with 3-D US were, on average, 34% higher and 24% lower than those obtained with MRI, respectively. A high correlation was observed for PSV (r = 0.79), whereas a lower correlation was observed for volume flow (r = 0.43). The overall standard deviations were ±5.7% and ±5.7% for volume flow and PSV with 3-D US, compared with ±2.7% and ±3.2% for MRI. Finally, the data were re-processed with a change in the parameter settings for the echo-canceling filter to investigate its influence on overall performance. PSV was less affected by the re-processing, whereas the difference in volume flow between 3-D vector flow imaging and MRI was reduced to ?9%, and with an improved overall standard deviation of ±4.7%. The results illustrate the feasibility of using 3-D US for precise and angle-independent volume flow and PSV estimation in vivo.     

Prenatal detection of ductal-dependent congenital heart disease: how can things be made easier?

OBJECTIVE: To improve the detection of ductal dependence in fetuses with severe anomalies of the outflow tracts by observing, with directional power Doppler, reverse flow through the aortic arch or ductus arteriosus in a transverse view of the upper mediastinum. METHODS: A slight cranial move of the ultrasound beam from the three-vessel view allows the transverse view of the aortic arch and ductus arteriosus to be visualized simultaneously. This view is orthogonal to the fetal body axis and parallel to the plane of the four-chamber view. In normal fetuses, directional power Doppler interrogation at this level identifies forward flow in both oblique vessels. RESULTS: We examined 43 fetuses with cardiac defects. In five of the cases, there was reversed flow in the aortic arch or ductus arteriosus in addition to severe anomalies of the outflow tracts, including four with hypoplastic left ventricle and one with pulmonary atresia. CONCLUSIONS: Prenatal detection of reversed flow in the aortic arch or ductus arteriosus is associated with complex congenital heart disease with major diminution of forward flow to the corresponding great vessels.     

产前超声横断面连续扫查三血管气管上多切面诊断胎儿心血管异常

目的 探讨产前超声横断面连续扫查三血管气管上多切面诊断胎儿心血管异常的价值。方法 采用横断面连续扫查三血管气管上多切面方法,观察502胎正常胎儿和521胎异常胎儿的三血管气管上多切面声像图特点。结果 由三血管气管切面开始向胎儿头侧移动探头,依次获得三血管气管切面;头臂静脉切面可显示头臂静脉、主动脉横弓;头臂动脉起始段切面可显示头臂动脉、左颈总动脉、左锁骨下动脉起始段横断面;双侧锁骨下动静脉切面可显示双侧锁骨下动脉及双侧锁骨下静脉长轴、双侧颈总动脉起始段横断面。502胎正常胎儿三血管气管上多切面均可通过连续扫查获得显示。521胎异常胎儿中,三血管气管上多切面扫查检出头臂静脉异常236胎,头臂动脉异常277胎,心上型肺静脉异位引流7胎,颈位主动脉弓1胎。结论 三血管气管上多切面连续扫查有助于产前超声诊断胎儿心血管异常。     

时空关联成像在胎儿心脏检查中的应用研究

目的 探讨时空关联成像（STIC）技术在胎儿心脏扫查及胎儿心血管畸形诊断中的应用价值。方法 选择孕龄在19～36 周的110例正常胎儿及32例已行二维超声心动图并拟诊为先天性心血管畸形的胎儿,应用STIC技术采集心脏容积数据,部分胎儿（24例）采集四腔心切面及胸部正中矢状面容积数据,存盘后进行脱机重建研究及回顾性分析,对二维常规超声与STIC方法获得的胎儿心脏图像进行比较。结果 110例中97例正常胎儿心脏超声检查获得满意的容积数据。97例正常胎儿心脏四腔心、五腔心、左心室流出道、右心室流出道（大动脉短轴）、三血管-气管切面、上下腔静脉长轴切面的显示满意率（分别为100%、97.6%、93.8%、91.7%、92.7%、89.6%）与常规二维扫查图像的满意率（分别为100%、100%、97.9%、96.9%、95.8%、93.8%）比较差异无统计学意义,而在73例只扫查胎儿四腔心切面为基础的容积数据获得的主动脉弓长轴、动脉导管弓切面的显示满意率（分别为6.8%、19.1%、）与常规二维扫描图像显示满意率（分别为91.7%、94.5%、）比较差异有统计学意义（P<0.05）,在24例扫查胎儿四腔心切面加胸部矢状切面为基础的容积数据获得的主动脉弓长轴、动脉导管弓切面图像显示满意率（分别为91.6%、87.5%、）与常规二维扫描图像显示满意率（分别为100%、100%、）比较差异无统计学意义（P>0.05）。32例行二维超声心动图诊断为先天性心脏病胎儿,共涉及心血管畸形51处,二维筛查时漏诊1处永存左上腔,容积数据后处理分析能完全重现并诊断,并能显示更多的非标准切面。结论 STIC技术扫描胎儿心脏四腔心切面加胸部正中矢状切面为基础的容积数据能获得完整的心脏切面,能对胎儿心血管畸形二维超声心动图诊断进行补充。     

Tomographic ultrasound imaging of the fetal heart: a new technique for identifying normal and abnormal cardiac anatomy.

OBJECTIVE: In 2003 and 2004, the American College of Radiology, the American Institute of Ultrasound in Medicine, and the American College of Obstetricians and Gynecologists published guidelines for the standard ultrasound examination of the fetus. Each group recommended that the outflow tracts of the fetal heart be examined if technically feasible. One method to accomplish this task is to perform a free-hand sweep of the transducer beam directed in a transverse plane from the 4-chamber view to the fetal neck. One problem with this approach is that the examiner may not direct the beam transversely and, therefore, may not accurately identify the outflow tract anatomy. METHODS: A new technology, tomographic ultrasound imaging (TUI), allows the examiner to obtain a volume data set that simultaneously displays multiple images at specific distances from the 4-chamber view. This study examined TUI technology for identifying normal and abnormal fetal cardiac anatomy with the use of either static or spatiotemporal image correlation volume data sets. RESULTS: The 4 views used in the screening examination of the outflow tracts of the fetal heart (4-chamber, 5-chamber, 3-vessel, and tracheal views) could be identified with the use of TUI technology in fetuses between 13 and 40 weeks' gestation. Examples of fetuses with abnormal cardiac anatomy of the outflow tracts (tetralogy of Fallot, transposition of the great vessels, and pulmonary stenosis) all showed abnormal anatomy on TUI. CONCLUSIONS: Tomographic ultrasound imaging technology enables the fetal examiner to evaluate the 4-chamber view and the outflow tracts in a systematic manner to identify normal and abnormal cardiac anatomy.     

Quantification of Flow Using Ultrasound and Microbubbles: A Disruption Replenishment Model Based on Physical Principles

Contrast-enhanced ultrasound (CEUS) is a promising clinical tool capable of noninvasively quantifying flow and relative vascular volume within the microcirculation. Quantification can be performed by recording the replenishment intensity time course of the imaging plane after the local disruption of agent during a constant infusion. Traditional analyses of the time-intensity curves have relied on mathematical functions (e.g., mono-exponential) that fail to consider the underlying physical principles of the flow system and the influence of the measurement device. In reality, the time-intensity curve reflects the hemodynamics and morphology of the vascular system being measured, the ultrasound field distribution and microbubble properties. We introduce a general analytic disruption replenishment model that attempts to account for these parameters and compare its performance to the established model in a flow phantom. Specifically, the proposed model incorporates the hemodynamic properties of the flow system (velocity distribution and vascular cross section); includes the elevation and axial plane pressure distributions; and accounts for the distinct high and low mechanical index (MI) disruption and detection boundaries. In addition, we demonstrated the importance of the ultrasound beam profile for accurate velocity quantification. It was shown that velocity estimates vary by up to 56% if the depth-dependent elevation thickness is not properly accounted for. Compared with the currently accepted mono-exponential model, the presented formalism was shown to be more robust in the presence of simulated motion artifacts and demonstrated better agreement in both the quality of the fit and estimation of velocity (∼3 to 10% vs. 90% error) for the same flow and acoustic conditions. (E-mail: hudsonjm@gmail.com)     

In Vivo Validation of Volume Flow Measurements of Pulsatile Flow Using a Clinical Ultrasound System and Matrix Array Transducer

The goal of this study was to evaluate the accuracy of a non-invasive C-plane Doppler estimation of pulsatile blood flow in the lower abdominal vessels of a porcine model. Doppler ultrasound measurements from a matrix array transducer system were compared with invasive volume flow measurements made on the same vessels with a surgically implanted ultrasonic transit-time flow probe. For volume flow rates ranging from 60 to 750 mL/min, agreement was very good, with a Pearson correlation coefficient of 0.97 (p < 0.0001) and a mean bias of ?4.2%. The combination of 2-D matrix array technology and fast processing gives this Doppler method clinical potential, as many of the user- and system-dependent parameters of previous methods, including explicit vessel angle and diameter measurements, are eliminated.     

Noninvasive assessment of wall-shear rate and vascular elasticity using combined ARFI/SWEI/spectral Doppler imaging system

The progression of atherosclerotic disease is a complex process believed to be a function of the localized mechanical properties and hemodynamic loading associated with the arterial wall. It is hypothesized that measurements of cardiovascular stiffness and wall-shear rate (WSR) may provide important information regarding vascular remodeling, endothelial function and the growth of soft lipid-filled plaques that could help a clinician better predict the occurrence of clinical events such as stroke. Two novel ARFI based imaging techniques, combined on-axis/off-axis ARFI/Spectral Doppler Imaging (SAD-SWEI) and Gated 2D ARFI/Spectral Doppler Imaging (SAD-Gated), were developed to form co-registered depictions of B-mode echogenicity, ARFI displacements, ARF-excited transverse wave velocity estimates and estimates ofwall-shear rate throughout the cardiac cycle. Implemented on a commercial ultrasound scanner, the developed techniques were evaluated in tissue-mimicking and steady-state flow phantoms and compared with conventional techniques, other published study results and theoretical values. Initial in vivo feasibility of the method is demonstrated with results obtained from scanning the carotid arteries of five healthy volunteers. Cyclic variations over the cardiac cycle were observed in on-axis displacements, off-axis transverse-wave velocities and wall-shear rates.     

3-D Intravascular Characterization of Blood Flow Velocity Fields with a Forward-Viewing 2-D Array

Risk stratification in coronary artery disease is an ongoing challenge for which few tools are available for quantifying physiology within coronary arteries. Recently, anatomy-driven computational fluid dynamic modeling has enabled the mapping of local flow dynamics in coronary stenoses, with derived parameters such as WSS exhibiting a strong capability for predicting adverse clinical events on a patient-specific basis. As cardiac catheterization is common in patients with coronary artery disease, minimally invasive technologies capable of identifying pathologic flow in situ in real time could have a significant impact on clinical decision- making. As a step toward in vivo quantification of slow flow near the arterial wall, proof-of-concept for 3-D intravascular imaging of blood flow dynamics is provided using a 118-element forward-viewing ring array transducer and a research ultrasound system. Blood flow velocity components are estimated in the direction of primary flow using an unfocused wave Doppler approach, and in the lateral and elevation directions, using a transverse oscillation approach. This intravascular 3-D vector velocity system is illustrated by acquiring real-time 3-D data sets in phantom experiments and in vivo in the femoral artery of a pig. The effect of the catheter on blood flow dynamics is also experimentally assessed in flow phantoms with both straight and stenotic vessels. Results indicate that 3-D flow dynamics can be measured using a small form factor device and that a hollow catheter design may provide minimal disturbance to flow measurements in a stenosis (peak velocity: 54.97 ± 2.13 cm/s without catheter vs. 51.37 ± 1.08 cm/s with hollow catheter, 6.5% error). In the future, such technologies could enable estimation of 3-D flow dynamics near the wall in patients already undergoing catheterization.     

Three-dimensional fetal echocardiography: gated versus nongated techniques.

The purpose of this study was to compare gated with nongated three-dimensional fetal echocardiography in terms of the ability to demonstrate fetal cardiac anatomy. We examined nine fetuses in utero using conventional two-dimensional sonographic imaging equipment, an electromagnetic position sensor, and a computer-graphics workstation. Free-hand sweeps were performed through the fetal heart and great vessels in either transverse or sagittal orientations with respect to the fetal heart. Seven transverse and five sagittal sweeps were selected for reconstruction and analysis. Cardiac gating was performed by using a temporal Fourier transform to determine the fundamental frequency of cardiac motion. Two-dimensional data from each sweep were reprojected to a series of volume data sets. Each series was then condensed to a single volume, so that each two-dimensional sweep could be compared with its respective gated and nongated volume data sets. The two-dimensional data were reviewed utilizing a display with forward and backward cineloop capability. The gated and nongated volume data sets were displayed interactively as a series of three orthogonal planes, with the ability of the observer to control the location of each image plane within the volume. The gated data were animated with variable display frame rates. Conventional two-dimensional imaging provided a fairly complete evaluation of the fetal heart when scanning included the four-chamber view with a sweep across the outflow tracts. Nongated three-dimensional fetal echocardiography allowed visualization of some structures and views not demonstrated with two-dimensional ultrasonography. Gated three-dimensional fetal echocardiography provided significantly better visualization and comprehension of cardiac anatomy than nongated three-dimensional fetal echocardiography. The superiority of gated over nongated three-dimensional fetal echocardiography appears to come from both improved image quality and the anatomic clues that derive from the ability to view cardiac motion.