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Published byBasil Banks Modified over 8 years ago
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Radiology Milliaperage
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The beam of radiation we use in dentistry may be described in two ways: 1.Quality = penetrating ability - energy of the photon beam 2.Quantity = amount - # of photons in beam Beam Intensity
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The dental x-ray unit typically has the following “controls” that will directly influence the quality and quantity of radiation: Exposure Timer (time) Milliamperage control (mA) Kilovoltage control (kVp or kVcp) Beam Indicating Device Length (BID) Intensity controlled by:
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Radiation Physics – X-ray Unit & Components X-ray control units may permit multiple adjustments: mA, kVp + time X-ray control units may be “simple” and only permit adjustments in TIME X-ray Unit Control Panel
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Radiation Physics – the practical side Radiation Beam Control: Quantity = amount mA – directly influences # of electrons striking target, hence # of photons produced. Process: thermionic emission Rule of Thumb: Increasing mA: 10 to 15 = 30% more radiation Decreasing mA: 15 to 10 = 30% less radiation mA - directly influences # of electrons striking target- therefore controls # of photons produced
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mAs Density (darker) mAs Density (lighter)
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Radiation Physics – the practical side Radiation Beam Control: Quantity = amount mA Time - influence length of time unit produces x-rays; direct proportionality: longer time = more x-rays; less time = fewer x-rays Rule of Thumb: Double time = 2x MORE radiation ½ time = 50% LESS radiation Time - length of time unit produces xrays directly affects # of xrays produced Longer time = more xrays Shorter time = fewer xrays
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mA and Exposure Time two factors usually combined Exposure time - longer time = more xrays produced mA and time together control quantity or # of xrays produced mA X seconds = mAs mA X impulse = mAi
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Relationship of mA and exposure time mAtime mA time
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