Three-dimensional fetal echocardiography: gated versus nongated techniques.

Abstract

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.

Real-time 3-Dimensional Fetal Echocardiography With an Instantaneous Volume-Rendered Display

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Rapid and facile, 3D imaging allows the acquisition of a volume data set in a matter of seconds, in comparison with the more prolonged interval typically required for conventional fetal cardiac imaging. Thus, whereas conventional fetal cardiac imaging requires a great deal of expertise, acquisition of volume data sets appears far less dependent on operator expertise.…”

“…Although the majority of work in fetal 3D sonographic cardiac imaging has focused on reconstructive techniques, [1][2][3][4][5][6][7][8][9][10][11]14 real-time 3D technology has recently emerged as a potentially superior approach to fetal car-diac imaging. 12,13,15 Although reconstructive techniques acquire a series of planar images over several seconds, real-time approaches acquire entire volumes (rather than single planes) instantaneously, using specialized 2D matrix, phased array transducers.…”

Prenatal Screening for Congenital Heart Disease

“…Abnormalities of the 4-chamber view or outflow tracts that may be missed with a single still-frame image or series of images likely would not be missed with even a 2-second clip of the beating heart. Visualization of valve and myocardial motion facilitates and enhances the evaluation of cardiac structure 3,12 (just ask any pediatric cardiologist) and would make it far less likely to miss a major structural heart defect. However, whereas the sonographer, during scanning, sees the fetal heart beating, the physician, during review, typically sees only 1 or more still-frame images.…”

Real-time three-dimensional fetal echocardiography: initial feasibility study.

“…Current methods of three-dimensional fetal echocardiography are limited by the challenges of gating the fetal heart, artifacts introduced into the reconstructed volume data sets by random fetal and maternal motion, and algorithms related to gating and position sensing. [1][2][3] One approach with the potential to overcome the difficulties mentioned above uses a two-dimensional phased array transducer 7 to sample a pyramidal volume at 20 volumes/s rather than sampling a series of sequential planar images. By imaging in real time this approach significantly reduces the need for cardiac or respiratory gating and minimizes the effects of random motion.…”

“…[1][2][3][4][5][6] This technique currently requires the acquisition of a series of tomographic images, identification of each pixel within each plane with its exact spatial coordinates, and subsequent reprojection to a volume or series of volumes. In addition, the dynamic display of cardiac motion requires an algorithm to locate each planar image at the appropriate point in the cardiac cycle.…”