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DR Imaging
Chapters 14, 15, 17, 21, 23 (Bushong) & 5 (Farber)
| Question | Answer |
|---|---|
| Spatial Resolution | the ability of an imaging system to resolve and render on the image a small high-contrast object |
| Spatial Frequency | relates to the number of line pairs in a given length, mm |
| Resolution | measure of the ability of a system to image two separate objects and visually distinguish one from the other |
| Modulation Transfer Function | a measure of the ability of a system to display the contrast of anatomic objects varying in size |
| Contrast Resolution | the ability to distinguish many shades of grey from black to white, affected by SNR, increases CNR |
| Window Width | image contrast |
| Window Level | image brightness |
| Postprocessing | chief advantage of digital systems |
| Dual-Energy Subtraction | removes superimposed structures so that the anatomic area of interest becomes more visible |
| Contrast Enhancement | alters the pixel values to increase image contrast |
| Edge Enhancement | improves the visibility of small, high-contrast structures, slightly increases image noise. Also, called high-pass filtering |
| Inversion | reverses the greyscale from the original image. Also known as black/white reversal |
| Smoothing | suppresses image noise (quantum noise, degrades spatial resolution. Also known as low-pass filtering |
| Equalization | makes unexposed areas lighter or darker, the effect is an image that has lower contrast so that dense and lucent structures can be better seen within the same image |
| Region of Interest | provides calculation of selected pixel values within the area of interest to provide quantitative information about the tissue |
| Stitching | multiple images are made into one image for viewing anatomic areas |
| Electronic Masking/Shuttering | removes regions surrounding the exposure field that provide no useful information or may negatively impact the histogram analysis |
| Valued of Interest | the rage of histogram data set that should be included in the displayed image |
| Exposure Indicator | provides a numeric value indicating the level of radiation exposure to the digital IR |
| Deviation Index | value that reflects the difference between the desired or target exposure to the IR and the actual exposure to the IR |
| Detective Quantum Efficiency | related to the absorption coefficient and to the spatial frequency of the image-forming x-ray beam |
| Lumen | basic unit of photometry, measures luminous flux |
| Luminous Flux | the fundamental quantity of photometry, the total intensity of light from a source |
| Illuminance | describes the intensity of light incident on a surface |
| Luminance Intensity | a property of the source of light, the luminous flux that is emitted into the entire viewing area; it is measured in lumens per steradian or candela |
| Photopic | bright-light vision with cones |
| Scotopic | dim-light vision with rods |
| Luminance | quantity that is like luminance intensity, another measure of the brightness source, units of candela per square meter or nit |
| Cosine Law | describes the luminous intensity of a digital display device. When a monitor is viewed straight on, the luminous intensity is maximum. When a monitor is viewed from an angle, the contrast and luminous intensity are reduced |
| Inverse Square Law | luminous intensity decreases in proportion to the inverse square of the distance from the source |
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