Image Formation/Processing/Display
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| What is each small region in the grid? | pixel
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| What is a grid of pixels called? | matrix
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| how do you determine the number of pixels in a matrix? | rows x columns (matrix size)
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| What is used to assign values to the pixels? | gray scale
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| What is the range of the gray scale? | -1000 to +1000
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| What coordinates does a pixel use? | X and Y
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| What coordinates does a voxel use? | X,Y, and Z
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| How is a voxel different than a pixel? | it is 3D and has volume
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| What is scan FOV? | the entire area used to collect data for a given body part
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| What is display FOV? | the size of the reconstructed image in the matrix
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| Which can be changed: scan FOV or display FOV? | display FOV
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| Attenuation coefficient depends on what? | 1.photon energy
2.atomic # of tissue
3.thickness of tissue
4.electron density
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| What is one photon sampling? | ray
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| What is one sample location from the pt body? | projection/view
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| What is the hounsfield units of Air? | -1000
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| What is the hounsfield units of Lung | -500 to -200
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| What is the hounsfield units of fat? | -200 to -50
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| What is the hounsfield units of water? | 0
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| What is the hounsfield units of blood? | 25
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| What is the hounsfield units of muscle? | 25 to 40
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| What is the hounsfield units of bone? | 200 to 1000
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| What is window width? | range of CT #s to be displayed in a image, contrast of the image
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| What is window level? | brightness of image/tissue
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| What is interpolation process? | used to divide data into slices at any arbitrary position
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| What is the thickness at pitch of 1? | collimation is equal to slice thickness
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| What is the thickness at pitch of 2? | slice thickness is 30% greater
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| A pitch of 1.5 is a: | 1.faster scan
2.less samples
3.less available mAs
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| A pitch of .75 is a: | 1.slower scan
2.more samples
3.more available mAs (more radiation)
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| What is Cine? | viewing in rapid sequence
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| What is MIP (maximum intensity) commonly used for? | CTA
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| What is convolution? | process of applying filtration
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| What are the filters used in image recon? | 1.sharp
2.smooth
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| What are sharp filters used for? | musculoskeletal
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| What are smooth filters used for? | abdomen
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| What views do scout images use? | AP, PA, Lateral
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| What are some characteristics of scout images? | large FOV, single projection, tissue superimposed
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| What are the different scanning methods? | 1.scout
2.conventional/serial scan
3.helical/spiral/volumetric scan
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| What is the process of conventional/serial scanning? | scan-stop-move
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| What is the process MPRs (multi planer recon) use? | image-raw data-image
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| What are the 2 steps of image recon? | 1.apply filter to raw data (convolution)
2.apply back projection or cone beam to raw data
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| What are commonly used matrix? | 128x128,256x256,512x512,1024x1024
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