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13 Cards in this Set
- Front
- Back
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Define mA
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The quantity of electrons moving through the x-ray tube during an exposure.
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What is the function of mA?
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To establish the desired quantity of electrons that will strike the anode during the exposure to produce various quantities of primary radiation.
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Explain how ma determines tube current.
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As the mA selector is turned up at the control panel, more current will pass through the filament circuit. This increases tube current.
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Explain how mA controls quantity of the x-ray beam and exposure rate.
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As mA increases so does the number of electrons which are able to cross the tube to reach the x-ray target.
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Explain how mA influences focal spot size.
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High mA exposures require a large focal spot and low mA exposures use the small focal spot.
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Explain the importance of the reciprocity law.
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A compatibility between the accumulation of radiation on the film caused by beam intensity and exposure time.
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Define calibration
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The mA selected is equal to the actual mA output.
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Explain the importance of calibration.
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Calibration is important when the technologist must deviate from the technique chart. If the generator is out of calibration, equal densities will not result at the same mAs values.
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Explain the role of mA in relationship to patient dose.
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As mA increases, the number of photons produced increases and patient dose increases.
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Explain the effect of mA on the radiographic image.
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As mA increases, more x-rays are produced, resulting in a greater accumulatino of x-rays on the film's emulsion.
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Explain the effect of time on the radiographic image.
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As time increases, x-rays are produced for a longer period of time, resulting in a greater accumulation of x-rays on the film's emulsion.
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Explain the important limitations to phototiming.
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Phototiming has difficulty in producing consistent radiographs when radiographing patients with a variety of diseases.
Little positioning latitude Reaction time of the photoelectric cell. The manual timer will override the phototimer device. |
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List some advantages of phototiming.
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1) Provide consistent densities from patient to patient. Quality is more predictable.
2) Radiographic contrast is relatively consistent. |
