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Digital Radiography
Ch. 23
| Question | Answer |
|---|---|
| What kind of radiography imaging systems utilizes a reusable image receptor or detector? | Digital |
| What else is a computer radiography CR referred to | A PSP technology |
| Photostimulable imaging plate (PSP, IP) is where? | Inside the cassette |
| What is the 2 step process of digital radiography? | PSP exposed and a CR reader using a laser scanner to process the IP. |
| Do digital radiography machines use cassettes? | No, flat panel IR's or detectors are permanent parts of the systems, cassettes not needed. |
| Some DR systems are now____. | Wireless |
| How many step process is DR and what is the process? | 1 step process, image goes directly to the computer. |
| 2 part process; Uses a scintillator ( x-rays converted to light then photodetectors converts light to electric signal ), electric signal is a analog signal, uses a CCD or a-SI with a TFT. | Indirect conversion. |
| 1 part process, does not uses a scintillator (x-rays convert to electric signal) uses a-Se with a TFT | Direct conversion. |
| Each binary Number is called a? | Bit |
| 8 bit = | 1 byte |
| What is a series of boxes laid out in rows and columns and gives formation to the image? | Matrix |
| Each box of an image matrix will display a? | Number value that can be transformed into density/brightness level. |
| The individual boxes in a matrix are called? | Pixels, voxels, or picture elements. |
| Pixel location can be determined by its? | Pixel address. |
| What are the 3 numbers that are in associated with each pixel? | 2 numbers define the address, and the shade of gray for intensity or density/brightness of the image at that location. |
| The number of boxes in a row multiplied by the column will give you the? | Total number of pixels in the matrix. |
| What is "FOV"? | Field of view, determined by the detector. |
| The____and____are independent | FOV and matrix size; The matrix size can be changed without affecting the FOV and vice versa. |
| Changes in the FOV or the matrix size will change the____. | Pixel size. |
| FOV/matrix size is | The size of the pixel. |
| ____ is a geometric property of image quality, the accuracy of structural lines recorded in the image. Also referred as detail, definition, or sharpness. | Spatial Resolution. |
| The number of shades in a pixel is determined by? | Grayscale Bit Depth |
| Digital standard for imaging is? | DICOM |
| DICOM stands for? | Digital Imaging and COmmunication in Medicine. |
| ____ allows images to be transferred between institutions. | DICOM |
| Based on the locations of pixels, spatial location usually describes as pixel location. (X, Y) | Spatial location Domains |
| Based on number of cycles per unit length, described as object size and contrast. | Spatial Frequency domains |
| Produce high frequency and high contrast | Small structures |
| Produce low frequency and low contrast | Large structures |
| A mathematical algorithm that changes an image from from spatial location domain to spatial frequency domain | Fourier Transformation (FT). |
| Returns an image to spatial location domain | Inverse FT |
| _____ , ______, and ______, are primarily intended to change the input values of the pixels to improve the quality of the output image | Point processing, local processing, and geometric processing. |
| A graph generated during initial processing from the image data that allows the digital system to find the useful signal in the anatomical regions of interest in the image. | Histogram |
| ____ is used to locate the minimum and maximum exposure values for the body part. | VOI; VALUE OF INTEREST |
| The computer corrects the image by shifting degenerated histogram to the correct area is also called | Histogram modification or stretching. |
| A wide histogram demonstrates ______ contrast | Higher |
| A ____ histogram demonstrates lower contrast | Narrow |
| Digital detectors have a _____ that would result in an image with low contrast if the computer did not adjust the contrast. | Linear response |
| ______ is applied to the data that would normally have a low contrast and gives the desired contrast for view. | A LUT (look up table). |
| What is the purpose of a LUT | Predetermined scale of contrast to the digital data |
| The ______________ is the range of densities that will be display. Controls contrast | Window width |
| ______ width has few densities, so the image will have higher contrast | Narrow width |
| Large width has lots of densities resulting in ______ | Low contrast |
| The _______ is the center of the window width and controls the brightness of the image. | Window Level |
| If window level is at the low-end of the scale, image will be____. If window level is that the high end, image will be ______ | Light, Darker. |
| _________ Only apply to a small group of pixels, although the operations will often be continue until all pixels have been subject to it. | Local processing operation also called group or area processing and kernelling |
| This type of filter is used to sharpening, smoothing, blurring, reduce noise, pull elements of interest from image. | Spatial frequency filter |
| This filter is uses a Fourier transform to convert the image into spatial frequency domain, then a high pass filter is applied to remove the low spatial frequency and produces a sharper image with edge enhancement and increased contrast. | High pass filtering (edge enhancement) |
| Uses a similar process that intentionally blurs the image. | Low pass filtering (smoothing) |
| Also called convolution. | Spatial location filtering |
| ________ processing operation are used to change the position or orientation of the pixels in the image. This allows rotation, magnification, other operations similar to digital photography. | Geometric processing operations |
| When matrix size increases; pixel size____, detail _____? | Pixel size decreases, detail increases. |
| ___________ has insufficient mAs and produces grainy image. | Quantum mottle noise |
| ___________ Random background information that is detected but not useful to the image. | Electronic system noise |
| _____ means little noise in image 100:1 | High S/N |
| ______ means high noise in image, decreases contrast 10:1 | Low S/N |
| _______ is a measure of these sensitivity and accuracy by which the IR converts incoming data to the output viewing device. | Detective quantum efficiency (DQE) |
| Digital radiography systems have DQE's of what | .3 to .7 or 30% to 70% |
| A low S number of 150 would indicate what? | Overexposed |
| A high S number of 250 would indicate what? | Underexposed |
| ______ Controls contrast for film and digital systems. | Kvp. |
| Some CR manufacturers recommend no more than 80 KVP for non-grid imaging due to the producing more what? | Compton scatter |
| What CR reader travel speed of IP through reader. The IP moves slowly through the reader. | Slow scan |
| What CR reader uses laser light in reader is rapidly reflected by an oscillating polygonal mirror that redirects the beam to a special lens called the F-theta Lens that focuses light on a cylindrical mirror that reflects the light toward the IP. | Fast scan |
| What type of scanning pattern does fast scan have? | Raster pattern. |
| This _______ reader has laser been collected/shape by Lens systems, scan is performed line by line, light emitted sent to CCD, CCD convert light into electric signal, singal sent to ADC and digitized. | Line Scan Reader |
| Flat panel DR; uses a photo conductor to convert x-ray energy. | Direct |
| Flat panel DR; Uses scintillators/ phosphors to convert x-ray energy. | Indirect |
| _________ distance midpoint of one pixel to midpoint of adjacent pixel; determines spatial resulution. | Pixel Pitch |
| ________ is a ratio of these sensing area of the pixel of the area of the pixel it self, where the x-rays are converted to light or to electric signals. | Fill factor |
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