CT and dual energy CT - Reconstruction
12 important questions on CT and dual energy CT - Reconstruction
Relation between attenuation and intensity and image brightness?
High attenuation is bright image.
What is the difference between a monochromatic and polychromatic x-ray beam?
How is an image reconstruction made?
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Why is a picture blurred after back projection?
What does a sharpening filter give you?
- Sharp edges
- More noise
What does a smoothing filter do?
- Lower spatial resolution
- Low edge details.
What is iterative reconstruction?
2. Forward projection; based on the estimate picture
3. Comparison of back projection and the from the forward projection
4. Reconstruct estimate. And repeat the process.
What is the reference of Hounsfield Units?
attenuation coefficient of intest - u of H20 / u H2O X 1000
When does filtering happen in the reconstruction process?
- It happens with the raw data.
When do you use which window? Narrow or wide?
When a tissue has not that much of differences. You can use a narrow window. You will have increase contrast. A little change in HU => high change in brightness.
So what kind of window do you chose for bone or for abdomen?
Abdomen => small differences => small window
What happens to the pixels with a value outside the window?
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