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Chap 2 Proc. Concept

Imaging 2 - digital

QuestionAnswer
Images obtained can be represented in 2 domains, based on how they are acquired. What are they spatial location and spatial frequency domain
"often the X location is referred to as the pixel number and the Y location as the line number." Such an image is said to be in which domain? spatial location
The FT converts a function in the time domain to a function in _____ domain. frequency. (time domain.... location domain?)
Small structures within an object (patient) produce ____ frequencies that represent the ___ in an image. Large structures produce _____ frequencies and represent ____ info in the image. small is high frequencies and detail, large are low frequencies and contrast.
Radiologists and techs would prefer to see images in which domain? spatial location
Five fundamental classes of operations: image enhancement, image restoration, image analysis, image compression, image synthesis.
Image enhancement- purpose of this class is to generate an image that is more pleasing to the observer.
Image enhancement* certain characteristics can be enhanced such as: contours and shapes
Image analysis class purpose? allows measurements and statistics to be performed
Image compression class purpose? reduce the size of the image in order to decrease transmission time and reduce storage space
Two forms of image compression? lossy and lossless
In _____ compression there is no loss of any information in the image when it is decompressed. In _______ compression there is some loss image detail. lossless, lossy
Lossless is aka? wavelet?
image synthesis purpose is "create images from other images or non image data" example: basis of CT and MR images made 3D
Pixels calculated : FOV/Matrix
The number of bits per pixel is the bit depth
M x N x k bits. "k bits" implies that....... every pixel in the digital image matrix M x N is represented by k binary digits. ex) a bit depth of 8 implies each pixel will have 2^8 gray levels or shades of gray
A bit depth of 8 implies that each pixel will have... 2^8 (or 256) gray levels/shades of gray
FOV decreases, no change in matrix size, what happens to pixels? decrease in size
bit depth has an effect on the what? number of shades of gray
3 steps to digitizing an image. scanning, sampling, quantization.
In the first stage of digitizing, _______, the image is first divided into what? Scanning. An array of pixels
The second step of digitizing, _____, involves measuring sampling. The brightness level of each pixel using a device such as a photomultiplier tube
the third step in digitizing, _________, is a process whereby the brightness levels obtained from sampling are... Quantization. Are assigned an integer called a gray scale.
Image quality is _____ with higher bit ADCs. better
A histogram is a graph of the number of pixels in the image having... the same gray levels plotted as a function of the gray levels.
A wide histogram implies ____ contrast and a narrow histogram will show ___ contrast. more, less
LUT. A steep slope results in an image with what kind of contrast? high
windowing can change the _____ and _____ of an image contrast and brightness
A digital image is made up of numbers, and by definition the range of numbers is defined as _______, and the center of the range is defined as the ______. window width, window level
window width controls contrast
window level controls brightness
A narrow WW provides what kind of image? high contrast (narrow histogram shows less contrast..)
When the WL is increased, what happens to the image? becomes darker
Sampling frequency and pixel pitch have what kind of relationship? Inverse.
Low resolution has more _____ but its faster. ____ speed. High resolution you need more ____ and its slower, but has less penumbra. ____ speed. penumbra. 200 speed. High needs more mAs, 100 speed
LUT is used to ___, ______, _____ contrast. refine, evaluate, correct
What do you do to mAs when you go up in speed class? go down in mAs
Speed class and mAs are ____. inverse
How can the relationship between mAs and speed class be solved mathematically? old mAs/new mAs = new speed/old speed
Matrix is composed of DELs
Created by: Zoest35
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