mA objectives
Terms
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copy deck
- Define mA
- The quantity of electrons moving through the x-ray tube during an exposure.
- What is the function of mA?
- To establish the desired quantity of electrons that will strike the anode during the exposure to produce various quantities of primary radiation.
- Explain how ma determines tube current.
- As the mA selector is turned up at the control panel, more current will pass through the filament circuit. This increases tube current.
- Explain how mA controls quantity of the x-ray beam and exposure rate.
- As mA increases so does the number of electrons which are able to cross the tube to reach the x-ray target.
- Explain how mA influences focal spot size.
- High mA exposures require a large focal spot and low mA exposures use the small focal spot.
- Explain the importance of the reciprocity law.
- A compatibility between the accumulation of radiation on the film caused by beam intensity and exposure time.
- Define calibration
- The mA selected is equal to the actual mA output.
- Explain the importance of calibration.
- 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.
- Explain the role of mA in relationship to patient dose.
- As mA increases, the number of photons produced increases and patient dose increases.
- Explain the effect of mA on the radiographic image.
- As mA increases, more x-rays are produced, resulting in a greater accumulatino of x-rays on the film's emulsion.
- Explain the effect of time on the radiographic image.
- 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.
- 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. - 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.