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in a pt coordinating system the z-axis is what?
head to toe
In a pt coordinating system the x-axis is what?
right to left
In a pt coordinating system the y-axis is what?
anterior to posterior
Pixel size = fov divided by?
If FOV decreases without a change in matrix size then what happens?
pixel size will decrease as well
Digitization consists of 3 steps...
scan, sample & quatize
Bone is white which is what number on a gray level?
Black is air and is what number on a gray level?
5 fundamentals of digitizing images are:
enhancement, restoration, analysis, compression, synthesis
Image enhancement does what?
makes image more pleasing to the eye
Image Restoration does what?
improves quality of images that have distortions
Image analysis does what?
allows measurements and statistics to be performed as well as image segmentation (3D)
Image Compression does what?
reduces the size of the image to decrease transmission time & reduce storage space
2 types of image compression are
Lossless & Lossy
- No loss of info
- has a ratio of 8:1 or less
- Some info is lost forever
- can have ratio above 8:1
- Is not clinically used
Image synthesis does what?
creates images from other images or non-image data. (ex is reconstruction techniques)
in Hounsfield Units Air is what?
In HU scale Bone is what?
Transformation is what?
A lossless step, image is transformed from gray scale values in spatial domain to coefficients in some other domain
3D visualization Techniques consist of?
Surface Rendering & Volume Rendering
- part of 3D visualization technique
- simple procedure
- surface of an object is created using contour data and shading the pixels to provide the illusion of depth (10% of data in 3Dspace)
- part of 3D techniques
- Much more sophisticated than Surface
- used all data in 3Dspace to provide additional info.
- Allows observer to view more details inside the object
Attenuation depends on
electrons per gram, atomic #, tissue density & radiation used
Displayed FOV can be what compared to the scanned FOV?
Less than or equal to
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