Three-dimensional ultrasound (3DUS) imaging is a new technique that allows imaging from volume sonographic data rather than conventional planar data. The volume data can be viewed as a three-dimensional object and displayed in multiplanar mode in three orthogonal planes or in various modes of rendering that can be selected singularly or combined to optimize the visualization of soft tissues, bony structures or vessels.
The 4D imaging has introduced a temporal dimension to the 3D volumetric scansion, associating movement to representation of volumes.
3DUS provides the ability to examine the embryo and the fetus at the first trimester in any arbitrary plane. Various studies have reported a better visualization of the structures in normal fetuses as well as malformed ones, regarding selected cases of facial structures, cranium, abdominal wall and limbs.
3DUS technique is also being considered for measurement of nuchal translucency and the evaluation of the nasal bones.
Several reports exist on the application of 3D-4D techniques regarding conjoined twins.
4DUS allows the evaluation of fetal motorial and behavioral patterns.
3D-4D techniques are seen as a powerful complement to conventional ultrasound, but not a substitution to it.
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