GE Voluson 730Expert Service Manual page 154

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IRECTION EVISION
5-2-2-1 3D Data Collection and Reconstruction (cont'd)
By changing the position of the cross-section, a variety of views of the underlying structure are obtained,
and these views can be used to understand a 3-dimensional structure in the body.
To complete survey a 3-dimensional structure in the body, it is necessary to collect 2D images which
span a volume containing the structure. One way is to sweep the imaging cross-section by translating
it in a direction perpendicular to the cross-section. Another example method is to rotate the cross
section about a line contained in the cross section. The Voluson® 730Expert Ultrasound System uses
the automated so called C-Scan for the motion perpendicular to automated B-scan. Once a
representative set of 2D cross-sections are obtained, standard reconstruction techniques can be used
to construct other 2D cross-sections, or to view the collection of the cross-sections as a 3D images.
5-2-2-2 3D Image Presentation
The basic technique for 3D image presentation is to combine the 2D cross –sections into an image
which represents how the volume of the data would appear from a particular viewing direction.
The mathematics behind this feature is called 3D-rendering. Such combined images are called
projections, because the data from the volume is projected onto a flat 2-dimensional surface(e.g. the
ultrasound system display.) This technique can be applied to any 2D ultrasound mode.
Several techniques can be used to aid the human observer in understanding the resulting 2D image as
a representation of a three-dimensional object. One is to rotate the volume of data, and present the
resulting sequence of 2D projections to the observer. The changing direction of observation helps the
observer to separate the features in the volume according to their distance from the observer.
5-2-2-3 3D Rendering
The 3D (volume) rendering is a calculation process to visualize certain 3D-structures of a scanned
volume by means of a 2D-image. The gray value for each pixel of the 2D-image is calculated from the
voxels along the corresponding projection path (analyzing beam) through the volume. The render
(calculation) algorithm, surface or transparent mode, determines how 3D-structures are visualized.
With the MagiCut function it is possible to cut off "3D artifacts" which hide regions that are of interest for
the diagnostic purpose.
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Section 5-2 - General Information
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