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Chap 23

Imaging 2 - old book

Direct conversion, _____ scintillator. Indirect conversion, ____ scintillator. without, with
Indirect detectors use a two part process involving a scintillator that does what? and a photodetector/diode that does what? scintillator converts x-ray photons to light, photodetector/diode converts light into an electrical signal
If the FOV remains the same, then as matrix size increases, the pixel size ____, creating a _____ image. decrease, sharper
The greater the matrix size for the same FOV, the better the ___________. spatial resolution
Spatial resolution is measured in line pairs per millimeter (lp/mm)
The number of shades of gray is determined by the ? grayscale bit depth
Digital images are represented in two domains based on what? how the image is acquired
Images in the _____________ domain are based on a matrix that has specific locations for each pixel. spatial location domain
Images in the ______ domain are based on the number of cycles per unit length. spatial frequency domain
Physicians and radiographers view images in the ____________, whereas physicists and engineers can extract info from the mathematical representations of the image in the _________ domain. spatial location domain, spatial frequency
3 image processing operations? point processing, local, and geometric
Point processing operations are those that are performed when between the receipt of the input image from the image receptor and the output image that is viewed on the monitor.
Point processing operations involve adjusting the value of an _____ pixel to the corresponding _____ pixel. input, output
Common point processing operation is called _______, which allows for adjustments with image brightness and contrast. grayscale processing. (this involves histogram and LUT and windowing)
A wide histogram demonstrates _____ contrast. higher
If the histogram values are concentrated in lower comparative values the images appears _____. dark or dim
The proper ____ will provide the proper grayscale, regardless of variations in kVp and mAs, resulting in consistent images. (unless the exposure is too far out of range..) LUT
_____ is a point processing operation that changes the contrast and brightness of the image on the monitor. windowing
A ____ window width will have few densities, so the image will have ____ contrast. narrow, high. (large WW has many grays, low contrast)
Spatial frequency filtering is considered a type of __________,. Spatial frequency processing is a ________. local processing operation, post processing function.
The Fourier transformation (FT) is the mathematical algorithm that is applied to change ...... an image from the spatial location domain to the spatial frequency domain.
An inverse FT does what? return an image back to the spatial location domain
Spatial location is usually described as the pixel location, x-coordinate represents ____ line, y-coordinate represents ____ line. horizontal, vertical
____ pass filtering (aka edge enhancement) uses a FR to convert the image into the _______ domain. high, spatial frequency
When matrix size increases and pixel size goes down, spatial resolution ______. increases
Greater bit depth provides better ________. density resolution
noise can be classified as either _________ or ________ electronic system or quantum mottle
Image noise has what relationship to contrast? inverse
Quantum mottle noise results from what insufficient quantity of photons from improperly set exposure factors
Detective quantum efficiency (DQE) is a measure of what the sensitivity and accuracy by which the image receptor converts the incoming data to the output viewing device
A perfect DQE with 100% accuracy would have a DQE of ____ 1
The DI is essentially a comparison between what the actual exposure and the proper exposure received by the image detector
Direct detectors have an active layer in the imaging plate that is what material? amorphous selenium (a-Se)
Indirect detectors have scintillators, these are made of either what two things? Cesium iodide, or gadolinium oxysulfide
TFTs. The _____ collects the electrical charges produced by either the amorphous selenium or silicon as an array or matrix of pixel size detectors elements (DEL). TFTs
Each DEL in a TFT has a switch and a storage/sensing area. When the switch for each DEL in a row is activated, what happens? the signal is sent to the computer.
Created by: Zoest35