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How is X-ray intensity measured?
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Intensity is measured in Roentgens (R or MGy a) or milliroentgens (mR) and is termed the x-ray quantity.
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What is a roentgen (mGy a)?
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A measure of the number of ion pairs produced in air by a quantity of x-rays.
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What are some other names for X-ray intensity?
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X-ray quantity, radiation exposure, X-ray quantity.
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Roentgen formula
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1R=2.58 x 10(-4) C/kg
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What is x-ray quantity?
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The number of x-rays in the useful beam.
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What are the factors affecting x-ray quantity?
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Milliampere-seconds (mAs), Kilovolt Peak (kVp), and Distance.
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Milliampere-seconds (mAs)
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X-ray quantity is directly proportional to mAs.
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MAs x-ray quantity formula
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I1/I2 = mAs1/mAs2
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KVp
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X-ray quantity varies approximately as the square of the change in kilovolt peak (kVp).
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KVp x-ray quantity formula
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I1/I2 = (kVp1/kVp2)2
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Distance
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X-ray quantity varies inversely with the square of the distance from the target (the inverse square law).
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Distance x-ray quantity formula
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I1/I2 = (D2/D1)2
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X-ray exposure of a patient can be estimated to a reasonable approximation with the use of what equation?
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X-ray quantity (mR) = k (mAs) (kVp)2/D2
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When the mAs is increased, x-ray quantity:
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Incrreases proportionately.
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When the kVp is increased, x-ray quantity:
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Increases in proportion to kVp2.
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