4D Imaging; Data Collection And Reconstruction; Image Presentation; Rendering - GE Voluson i BT06 Service Manual

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5-2-2 3D/4D Imaging
The Voluson i / Voluson e Ultrasound System will be used to acquire multiple, sequential 2D images
which can be combined to reconstruct a three dimensional image. These 3D images are useful in
visualizing three-dimensional structures, and in understanding the spatial or temporal relationships
between the images in the 2D sequence. The 3D image is presented using standard visualization
techniques, such as surface or volume rendering.
5-2-2-1 3D Data Collection and Reconstruction
2D gray scale images including Color Flow or Power Doppler information may be reconstructed.
The acquisition of volume data sets is performed by sweeping 2D-scans with special transducers
(called 3D-transducers) designed for the 2D-scans and the 3D-sweep.
2D ultrasound imaging modes are used to view a two dimensional cross-sections of parts of the body.
For example in 2D gray scale imaging, a 2 dimensional cross-section of a 3-dimensional soft-tissue
structure such as the heart is displayed in real time. Typically, the user of an ultrasound machine
manipulates the position and orientation of this 2D cross-section in real time during an ultrasound exam.
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 completely 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 i / Voluson e 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
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.
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Figure 5-2 Principle: Volume Rendering
Chapter 5 - Components and Functions (Theory)
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