Stack #735079
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| mAs literally determins what | the number of electrons boiled off of the filament
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| what imaging system has a linear exposure relationship? | digital
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| over exposed or underexposed between the two which one would be least likely to be repeated? | overexposed
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| ___ represents the different absorbtion characteristics of the body | density
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| with film/screen systems image density is represented by twhat? | Black metallic silver deposit patterns
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| What happens to density as processing developer temp. increases? | it increases
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| what happens to density if collimation is increased? (field size is made smaller?) | it decreases
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| the intensity of a beam is less on which end of the tube? | Anode
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| all other factors remaining constant, if the intinsifying screen is switched to a faster one, what effect will it have on density? | it increases
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| As kVp increases and everything else remains constant what happens to density | it increases
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| what is the absorbing material in a grid? | lead
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| according to the inverse square law if the sistance is reduced to 1/2 the intensity will? | increase by a factor of 4
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| total filtration in the x-ray tube head assembly affects density by___ | removing low energy photons
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| what happens to density with increase in tissue thickness? | it will decrease
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| which set will produce the highest contrast? 50@20, 58@10, 67@5, 77@2.5 | 50@20
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| the lower the kVp the _____ resultant of contrast | higher
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| what tissue group will likely have the greatest xray absorption? | bone
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| which difference in densities will have the lowest contrast? 1.8, 1.5, 1.0, 0.5 | 0.5 because the lowest difference between densities will present low contrast
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| where does black metallic silver formation begin? | sensitivity speck
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| what layer in general film is not duplicated? | the base
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| which layer is manufactures to reduce eye strain? | the base
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| a grid will _____ scatter production... how/why? | decrease, it only reduces the amount of scatter that reaches the receptor...
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| an increase in developer time will ____ contrast | decrease
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| a compensating filter will ________ contrast | decrease
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| scatter _____ contrast | decreases
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| collimation ____ contrast | increases
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| the level or degree of penetration of the xray beam is a primary factor in determining _______ | the scale of contrast
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| the higher the kvp and mAs the ________ density | greater the
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| the lower the kVp the ____ the contrast | higher
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| scatter, patient dose, density... which one does kVp affect? | all of them
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| primary controller of density | mAs
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| ___ literally controls the current through the xray tube | mAs
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| what determins the energy of the x-ray beam? | kVp
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| 20 mAs is used at 40'' SID what will the mAs be at 72 '' SID | 65 mAs
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| 24 mAs is used for a slow speed screen... what would the mAs be for a fast moving screen? | 6 new mAs=24*(1/4)
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| if the collimation field is made smaller what will happen to the density if the mAs is not adjusted? | it will decrease
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| purpose of a grid? | absorb scatter
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| 20 mAs is used for a non grid tech. what mAs should be used for an 8:1 grid? | 80
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| increasing the screen speed allows for a reduction in ____ needed | mAs
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| if changed from a 11x14 cassette to a 10x12 cassette what adjustment needs to be made and why? | increase mAs because the photons that would have exposed the patient or the image receptor are removed.
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| to obtain a higher scale of contrast you must _____ kVp and ____mAs | decrease;increase
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| for every 4-cm change in tissue thickness mAs must be changed by ____ | a factor of 2
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| ____ controls the overall blackness of a radiograph? | mAs
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| the ____ the SID and the ____ the OID the sharper the image | longer;shorter
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| films with thicker emulsions or larger silver halide crystals will have ______ sharpness | less
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| in digital, changing a negative image to a positive image is called what? | image inversion
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| adjusting the brightness and contrast is called what? | window and leveling
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| in a psp plate the trapping of electrons in the conduction band creates what? | latent image
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| which kVp is capeable of producing the lowest contrast? 50,60,70,80 | 80, the higher th kVp the more penetration resulting in a low contrast image
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| which kVp setting will provide the most kenetic energy to filament electrons? | 100 the higher the kVp the more energy
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| which xray energy would have the lightest shades ? 20 50 80 or 100 | 20 less energy more chance of the photons being absorbed in the body less hitting the IR
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| which tissue group has the lowest water content? | fat
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| which tissue group has the highest water content? | muscle
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| what is the primary absorber of xrays in bone? | calcium
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| in which layer of the intensifying screen is xray energy converted into light? | active layer
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| which layer of film contains halide crystals? | emu;sion
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| once the halide crystals are exposed the sensitivity speck will first aquire what charge? | negative
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| why is scatter exposure undesirable? | it decreases contrast
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| compensating filters in effect _____ tissue thickness and density | increase
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| which OID would result in the greatest increase in radiographic contrast? 1,4,6,12 | 12
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| positive contrast media will ____ contrast | increase
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| what increases the voltage to kilovoltage in the xray circuit? | step up transformer
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| if the lead strips are 4.0 mm high and are separatedby an interspace of 025mm what is the grid ratio? | 4.0/.25 = 16:1
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| if lead strips are 2.0mm high and are separated by an interspace of.25mm what is the grid ratio? | 2.0/.25=8:1
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| s radiograph is produced using 85@8 without a grid. a second film is requested using an 8:1 grid with a conversion factor of 4 what mAs is needed? | 8 * 1/4 = 32/1 = 32 mAs (cross multiply
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| 1st radiograph is 85@10 without a grid what would be the mAs if using a 16:1 grid?(conversion factor of 6) | 10* 1/6 = 60/1 = 60 mAs
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| 1st image used 85@30 with a 12:1 grid 9conversion factor 5) 2nd film will be same tech. with a 16:1 grid (conversion of 6) what mAs is needed | 30* 5/6= 180/5 = 36 mAs
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| what are the grid-conversion factors for no grid, 5:1, 8:1, 12:1, and 16:1 grids? | 1,3,4,5,6
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| when the patient thickness is more that 10cm the kVp should be | greater than 60
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| transmission is responsible for what? | the dark areas on the image
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| absorption is responsible for | the light areas
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| the higher the frequency of a grid the ____ the interspace must be... & the ___the grid ratio | thinner;higher
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| contrast is _____ when a grid is used | doubled
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| what will go down, what must be increased, when a grid is placed in beam? | density will go down, exposure factors must be increased to compensate
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| parallel linear grid | all lead sstrips are parallel to eachother, they absorb a large amount of the primary beam resulting in some cut-off
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| with a decrease in SID grid cut-off will | increase
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| criss-cross ot cross hatched or cross grid | horizontal lead strips, vertical lead strips, primary beam must be centered perp. to grid, grid must remain flat
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| focused grid | fabricated so the strips are parallel to the primary xray path across the entire image receptor. minimizes grid cut-off
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| focused linear grids | lead strips are angled to match divergence of beam, primary beam will align with interspace material, scatter absorbed by lead strips
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| focused linear grids | convergence line, narrow positioning latitude, improper centering results in periphereal cut-off, only useful at present SID distance
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| which grids require careful alignment with tube? | higher frequency grids
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| what are the four main grid errors? | off-level, off-center, off focus, upside down
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| the central axis is not perpendicular to the grid, and if partial cut off occurs over the entire image receptor and comes out underexposed what type of error is this? | off level
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| when a focused grid has partial grid cut-off over t he entire image nad it looks underexposed what type of error is it? | off center
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| if a grid is not positioned at the specified focal distance, grid cut-off occurs and the optimal density decreases with distance from the central ray... cut off is toward the edge of image... what error? | off focus
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| if complete grid cutoff occurs except in the central region of the central ray what error is it? | upside down grid
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| which grid is better, focused or parallel? | focused
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| what are the three factors to consider with grid selection? | kVp, degree of clean-up, patient dose
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