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21 Cards in this Set
- Front
- Back
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Image Reconstruction
What is back Projection? |
A calculation used for reconstructing the final CT images from the raw data by adding together the attenuation information collected from all of the projections
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Image Reconstruction
A reconstruction filter applied to the raw data during image reconstruction is called what? |
Convolution
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Image Reconstruction
Sharp reconstruction filters are often used for what? |
For visualizing musculoskeletal detail
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Image Reconstruction
Smooth reconstruction filters are often used for what? |
Visualizing soft tissue contrast
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Image Reconstruction
What is a cone beam? |
Very thick xray beam, more than about 20mm, the beam of photons do not just diverge like a fan beam, but it also diverges along the, long direction of the patient table, in whats know as a cone beam
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Image Reconstruction
Why is it called cone beam? |
Because the beam is no longer flat like a fan, but rather three-dimensional like a cone
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Image Reconstruction
Describe cone beam artifact. |
"Spoke" or "Star like" appearence on structures at the edges of an image
*does not occur in the center of the image only on the edges |
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Image Reconstruction
Cone beam reconstruction is the calculation used for reconstructing the final CT images from the raw data on what type of CT scanner? |
MDCT scanners which have the ability to collect more than four slices in a single rotation
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Image Reconstruction
What are the two types of Image Reconstruction? |
Back projection and cone beam reconstruction
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Post Processing Techniques
What are the 5 post processing techniques on reconstruction? |
-Retrospective Reconstruction
-Multi-Planar Reconstruction -3D Shaded Surface Display(SSD) -Volume Rendering (VR) -Maximum Intensity Projection(MIP) |
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Post Processing Techniques
What is the major downfall of retrospective reconstruction? |
It requires raw data, which is lost once that portion of the raw data storage device is overwritten
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Post Processing Techniques
On MDCT scanner, a retrospective reconstruction is commonly used for what? |
To modify the reconstructed slice thickness
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Post Processing Techniques
Multi planar reconstruction allows for what? |
The reconstruction of images in planes that would otherwise be difficult or impossible to acquire with CT
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Post Processing Techniques
Multi planar reconstruction requires what? What is not used? |
-Only the image data
-The raw data is not utilized |
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Post Processing Techniques
3D shaded surface display reconstructs what? |
Images if the surface of the anatomical structure
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Post Processing Techniques
How does the 3D SSD program begin? |
By stacking the transverse slices to forn a colume of anatomical data
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Post Processing Techniques
What is a major advantage of Volume Rendering(VR) reconstruction? |
Volume Rendering can incorporate information from the entire image data set, rather than just a surface, into the post processed images, enabling visualization of structures above and below the surface
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Post Processing Techniques
Maximum Intensity Projection(MIP) is typically used for what? |
CT Angiography (CTA) studies
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Post Processing Techniques
How are MIP images generated? |
From transverse slices of a CTA study by projecting the brightest pixels into a plane
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Post Processing Techniques
What are disadvantages of MIP? |
MIP does not provide 3D information and in regions of overlapping densities, the more highly attenuating structure will mask the less attenuated structure
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Post Processing Techniques
When are the most accurate MIP results obtained? |
When a small volume of interest is selected
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