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Chap 23
Imaging 2 - old book
| Question | Answer |
|---|---|
| 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. |
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