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40 Cards in this Set
- Front
- Back
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degree of overall blackening on xray film
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density
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created by deposits of black metallic silver in the xray film that have been exposed to light or xrays, the processed
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density
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measure of the number of xray photons in the useful beam, output, or exposure.
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Beam Quantity
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mA, time, mAs, kVp, Distance and filtration
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Factors affecting Beam Quantity
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measurement of the penetrating ability of the beam and the distance of the beam travels in matter
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Beam Quality
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Produce high energy, travel farther andd are more penetrating
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Hard xrays
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Produce low energy, travel less and are less penetrating
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Soft xrays
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KVp and Filtration
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Factors affecting Beam Quality
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directly proportional to quantity
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Milliamerpage-seconds (mAs)
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Measurement of xray tube current or number of electrons crossing the tube
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mAs
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Increasing ? increases the number of electrons
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mA
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Directly proportional to tube current
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mA
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25 - 1500
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mA Ranges
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mA and Density
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Directly Proportional
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Time and Density
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Directly Proportional
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Controls density
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mAs
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Affects Density
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kVp
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SID and Density relationship
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Inversely Proportional
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OID and density relationship
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Inversely Proportional AIR Gap
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Grid with High Ratio
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Reduces density
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Large Collimation field size produces more scatter therefore
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Increases density
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An increase in filtration has what effect on the the amount of radiation in the beam
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Filtration REDUCES the amount of radiation in the beam.
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A higher speed screen will produce
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more light and more density
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What type of relationship do Developer temperature and density have?
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Directly Proportional
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Can electrons be focused?
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Yes Extra negative charge on the focusing cup repels electrons
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Can photons be focused?
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NO
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What CONTROLS quality
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kVp, Increasing kVp will increase the speed and energy of the electrons, which affects the penetrating power
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Increasing kVp will...
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rapidly increase the quantity or intensity of the beam.
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What is the relationship between quanity and kVp
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Directly proportional to the square of the ratio of the change in kVp. (doubling kVp produces a fourfold increase in the amount of xray photons.
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What is the rule regarding the Density relationship to kVp?
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15% Rule An increase of 15% in kVp is equivalent to doubling the mAs in terms of radiographic density, conversely 15% decrease = to having the mAs in terms of density.
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X ray intensity from a source (SID) follows what law?
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Inverse Square Law
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The xray beam diverges from the source or focal spot.
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SID
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The beam becomes larger on all four sides as the distance increases
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SID
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The xray beam diverges from ...
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the source or focal spot (SID)
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The intensity of radiation at th set distance is inversely proportional to the square of the distance
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Inverse Square Law
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To compensate for loss of radiation intensity when INCREASING DISTANCE from the source, INCREASE the mAs
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mAs1 / mAs2 = D1 / D2
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When distance from a source to the image receptor is doubled, the factor of mAs will need to be quadrupled in order to cponmpensate for the loss of radiographic density
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2 x D = 4x mAs
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Aperture diaphragms, cones, cylinders and collimators
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Beam restricters
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Larger the beam size the ..... the radiographic density
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Larger...
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Principle factors that increase density
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Highest mAs
Highest kVp Fastest film/screen combo lowest grid ratio Smallest area of collimation Shortest distance SID/OID Greatest development/time, temp and replenishment rate of processor Anode heel effect (Cathode over thickest part of body) |
