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One way to alter image contrast and/or density digitally is through
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The term windowing refers to
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COMPREHENSIVE IMAGE
| Question | Answer |
|---|---|
| One way to alter image contrast and/or density digitally is through | windowing |
| The term windowing refers to | some change made to window width and/or window level |
| Change in window width affects change in | the number of gray shades, that is, image contrast |
| Change in window level affects change in | the image brightness, that is, optical density |
| Windowing and other postprocessing mechanisms permit the radiographer to affect changes in the image and to produce "special effects" such as | edge enhancement, image stitching (useful in scoliosis examinations), image inversion, rotation, and reversal |
| Using fixed-mAs and variable-kVp technical factors, each centimeter increase in patient thickness requires what adjustment in kilovoltage? | Increase 2 kVp |
| A film artifact usually will appear as a plus-density (dark) artifact if it is produced before or after exposure? | before |
| A film artifact usually will appear as a minus-density (light) artifact if it is produced before or after exposure? | after |
| Quantum mottle is a grainy appearance on a finished radiograph that is seen especially in fast-imaging systems or slow-imaging systems? | fast |
| What does quantum mottle look like? | it has a spotted or freckled appearance |
| Which would be more likely to cause quantum mottle, low mAs or high mAs? | low mAs |
| Which is more likely to cause quantum mottle, low kVp or high kVp? | high kVp |
| The sensitometric curve may be used to | 1. identify automatic processing problems. 2. determine film sensitivity. |
| The sensitometric, or characteristic, curve is used to illustrate the relationship between exposure and | the resulting film density |
| How does a sensitometric curve predict a film emulsion's response(speed, sensitivity)? | by determining how long it takes to record a particular density |
| The sensitometric curve is used in sensitometry to monitor | automatic processing efficiency and consistency |
| A film is given a series of predetermined exposures and processed, The resulting densities are plotted, and the resulting curve is compared with a known correct curve, a known correct curve | processing difficulties |
| The sensitrometric curve illustrates the effects of exposure and processing on | radiographic film emulsion |
| Size distortion is | magnification |
| Shape distortion is a result of improper alignment of | the x-ray tube, the part being radiographed, and the image recorder |
| the two types of shape distortion are | foreshortening and elongation |
| The shape of various structures can be radiographically misrepresented as a result of | their position in the body, when the part is out of the central axis of the x-ray beam, or when the central ray is angled |
| Which type of error results in grid cutoff at the periphery of the radiographic image? | Off-focus |
| If FOV increases, pixel size | increases |
| Geometric unsharpness is most likely to be greater | at the cathode end of the image |
| If 10% of the illuminator's light passes through the film, that film has a density of | 1 |
| Which of the following can affect histogram appearance? | 1. Centering accuracy 2. Positioning accuracy 3. Processing algorithm accuracy |
| Angulation of the part with relation to the IR results in | foreshortening of the object |
| Tube angulation causes | elongation of the object |
| line focus principle | as the target angle decreases, the effective focal spot decreases (providing improved recorded detail), but the actual area of electron interaction remains much larger (allowing for greater heat capacity) |
| Does a steep (small) target angle increases or decrease the heel affect? | increase |
| The term field of view is used to describe | how much of the patient (eg, 150-mm diameter) is included in the matrix |
| The factors that affect the recorded detail of traditional screen/film imaging are | focal spot size, source-to-image distance (SID), object-to-image distance (OID), film/screen speed, and motion |
| Developing agents | change the exposed silver bromide crystals to black metallic silver, thus producing a manifest image |
| The fixer solution | removes the unexposed silver bromide crystals from the emulsion and hardens the gelatin emulsion, thus ensuring permanence of the radiograph |
| Which of the following functions to increase the mA? | Increasing the heat of the filament |
| A screen lag test is performed by radiographing a phantom using an empty cassette-image receptor, then loading it with film and leaving for it a few minutes. | If, after processing, there is any indication of an image, there is most probably screen lag. |
| Which of the following pathologic conditions require(s) a decrease in exposure factors? | 1. Pneumothorax 2. Emphysema 3. Multiple myeloma |
| Radiographic contrast is a result of | 1. differential tissue absorption. 2. emulsion characteristics. |
| Luminescence | the production of energy in the form of light |
| A film emulsion having wide latitude is likely to exhibit | low contrast |
| A gentle curve (as opposed to a steep curve) usually indicates a film with | slow speed, low contrast, and more latitude. |
| Grid ratio is defined as | the ratio between the height of the lead strips and the width of the distance between them (ie, their height divided by the distance between them). |
| anode angles of 10 degrees or less increase what? | anode heel effect |
| The iodine-based contrast material used in intravenous (IV) urography gives optimum opacification at what kVp? | 60 to 70kvp |
| how to find percentage difference between 2 numbers | X and Y is: Y/X - 1 |
| The function(s) of automatic beam limitation devices include | reducing the production of scattered radiation |
| Grid frequency refers to | the number of lead strips per inch |
| Factors that contribute to an increase in the intensification factor generally function to increase or decrease resolution? | decrease |
| As intensification factor increases, does radiographic density generally increase or decrease? | increase |
| Which of the following factors contribute(s) to the efficient performance of a grid? | 1. Grid ratio 2. Number of lead strips per inch 3. Amount of scatter transmitted through the grid |
| The greater the number of lead strips per inch | the thinner and less visible they will be on the finished radiograph |
| The function of a grid is to | absorb scattered radiation in order to improve radiographic contrast |
| The selectivity of a grid is determined by | the amount of primary radiation transmitted through the grid divided by the amount of scattered radiation transmitted through the grid |
| Characteristics of digital radiographic imaging include | 1. solid state detector receptor plates. 2. direct-capture imaging system. 3. immediate image display. |
| The fact that x-ray intensity across the primary beam can vary as much as 45% describes the | anode heel effect |
| Over- or underexposure under the anode is usually the result of | exceeding the focusing distance limits in addition to being off-center |
| Which of the following units is used to express resolution? | 1. Line-spread function 2. Line pairs per millimeter |
| Which of the following will result if developer replenishment is inadequate? | Images with excessively low contrast |
| The formula used to determine magnification factor is: | MF = SID/SOD |
| The formula for magnification factor is | MF = image size/object size. |
| The atomic number of the tissues under investigation is directly related to their | attenuation coefficient |
| To produce a just perceptible increase in radiographic density, the radiographer must increase the mAs by | 30% |
| The violet light emited by the photostimulable phosphor (PSP) is transformed into the image seen on the CRT by the | ADC |
| The latent image appears as the PSP is scanned by | a narrow high-intensity helium-neon laser to obtain the pixel data |
| As the plate is scanned in the CR reader, it releases a violet light—a process referred to as | photo-stimulated luminescence |
| The luminescent light from the plate is converted to | electrical energy representing the analog image |
| The electrical energy is sent to an analog-to-digital converter (ADC) where it is | digitized and becomes the digital image that is eventually displayed (after a short delay) on a high-resolution monitor and/or printed out by a laser printer |
| Which of the following pathologic conditions are considered additive conditions with respect to selection of exposure factors? | 1. Osteoma 2. Bronchiectasis 3. Pneumonia |
| focal spot angle is usually | 12° to 17° |
| The steepness of the characteristic curve is representative of | image contrast |
| The steeper the curve, the greater the density differences and the higher the | contrast |
| The speed of the film is determined by | the curve's position on the log relative scale: When comparing two or more characteristic curves, the faster film lies |
| The faster the film speed, the less the | exposure latitude |
| In digital imaging, pixel size is determined by | dividing the FOV by the matrix. |
| Antihalation backing is | a component of single-emulsion film that prevents crossover of fluorescent light within an image receptor. |
| How efficiently the phosphors detect and interact with the x-ray photons is termed | quantum detection efficiency |
| How effectively the phosphors make this energy conversion is termed | conversion efficiency |
| The greater the percentage of scattered radiation absorbed compared to absorbed primary radiation, the greater the | "selectivity" of the grid |
| Recorded detail is improved using | a small focal-spot size, largest practical SID, shortest possible OID, and slowest practical screen/film combination and avoiding motion of the part being imaged. |
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jen.