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Stack #735079
| Question | Answer |
|---|---|
| mAs literally determins what | the number of electrons boiled off of the filament |
| what imaging system has a linear exposure relationship? | digital |
| over exposed or underexposed between the two which one would be least likely to be repeated? | overexposed |
| ___ represents the different absorbtion characteristics of the body | density |
| with film/screen systems image density is represented by twhat? | Black metallic silver deposit patterns |
| What happens to density as processing developer temp. increases? | it increases |
| what happens to density if collimation is increased? (field size is made smaller?) | it decreases |
| the intensity of a beam is less on which end of the tube? | Anode |
| all other factors remaining constant, if the intinsifying screen is switched to a faster one, what effect will it have on density? | it increases |
| As kVp increases and everything else remains constant what happens to density | it increases |
| what is the absorbing material in a grid? | lead |
| according to the inverse square law if the sistance is reduced to 1/2 the intensity will? | increase by a factor of 4 |
| total filtration in the x-ray tube head assembly affects density by___ | removing low energy photons |
| what happens to density with increase in tissue thickness? | it will decrease |
| which set will produce the highest contrast? 50@20, 58@10, 67@5, 77@2.5 | 50@20 |
| the lower the kVp the _____ resultant of contrast | higher |
| what tissue group will likely have the greatest xray absorption? | bone |
| 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 |
| where does black metallic silver formation begin? | sensitivity speck |
| what layer in general film is not duplicated? | the base |
| which layer is manufactures to reduce eye strain? | the base |
| a grid will _____ scatter production... how/why? | decrease, it only reduces the amount of scatter that reaches the receptor... |
| an increase in developer time will ____ contrast | decrease |
| a compensating filter will ________ contrast | decrease |
| scatter _____ contrast | decreases |
| collimation ____ contrast | increases |
| the level or degree of penetration of the xray beam is a primary factor in determining _______ | the scale of contrast |
| the higher the kvp and mAs the ________ density | greater the |
| the lower the kVp the ____ the contrast | higher |
| scatter, patient dose, density... which one does kVp affect? | all of them |
| primary controller of density | mAs |
| ___ literally controls the current through the xray tube | mAs |
| what determins the energy of the x-ray beam? | kVp |
| 20 mAs is used at 40'' SID what will the mAs be at 72 '' SID | 65 mAs |
| 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) |
| if the collimation field is made smaller what will happen to the density if the mAs is not adjusted? | it will decrease |
| purpose of a grid? | absorb scatter |
| 20 mAs is used for a non grid tech. what mAs should be used for an 8:1 grid? | 80 |
| increasing the screen speed allows for a reduction in ____ needed | mAs |
| 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. |
| to obtain a higher scale of contrast you must _____ kVp and ____mAs | decrease;increase |
| for every 4-cm change in tissue thickness mAs must be changed by ____ | a factor of 2 |
| ____ controls the overall blackness of a radiograph? | mAs |
| the ____ the SID and the ____ the OID the sharper the image | longer;shorter |
| films with thicker emulsions or larger silver halide crystals will have ______ sharpness | less |
| in digital, changing a negative image to a positive image is called what? | image inversion |
| adjusting the brightness and contrast is called what? | window and leveling |
| in a psp plate the trapping of electrons in the conduction band creates what? | latent image |
| 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 |
| which kVp setting will provide the most kenetic energy to filament electrons? | 100 the higher the kVp the more energy |
| 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 |
| which tissue group has the lowest water content? | fat |
| which tissue group has the highest water content? | muscle |
| what is the primary absorber of xrays in bone? | calcium |
| in which layer of the intensifying screen is xray energy converted into light? | active layer |
| which layer of film contains halide crystals? | emu;sion |
| once the halide crystals are exposed the sensitivity speck will first aquire what charge? | negative |
| why is scatter exposure undesirable? | it decreases contrast |
| compensating filters in effect _____ tissue thickness and density | increase |
| which OID would result in the greatest increase in radiographic contrast? 1,4,6,12 | 12 |
| positive contrast media will ____ contrast | increase |
| what increases the voltage to kilovoltage in the xray circuit? | step up transformer |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| what are the grid-conversion factors for no grid, 5:1, 8:1, 12:1, and 16:1 grids? | 1,3,4,5,6 |
| when the patient thickness is more that 10cm the kVp should be | greater than 60 |
| transmission is responsible for what? | the dark areas on the image |
| absorption is responsible for | the light areas |
| the higher the frequency of a grid the ____ the interspace must be... & the ___the grid ratio | thinner;higher |
| contrast is _____ when a grid is used | doubled |
| 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 |
| parallel linear grid | all lead sstrips are parallel to eachother, they absorb a large amount of the primary beam resulting in some cut-off |
| with a decrease in SID grid cut-off will | increase |
| 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 |
| focused grid | fabricated so the strips are parallel to the primary xray path across the entire image receptor. minimizes grid cut-off |
| focused linear grids | lead strips are angled to match divergence of beam, primary beam will align with interspace material, scatter absorbed by lead strips |
| focused linear grids | convergence line, narrow positioning latitude, improper centering results in periphereal cut-off, only useful at present SID distance |
| which grids require careful alignment with tube? | higher frequency grids |
| what are the four main grid errors? | off-level, off-center, off focus, upside down |
| 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 |
| 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 |
| 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 |
| if complete grid cutoff occurs except in the central region of the central ray what error is it? | upside down grid |
| which grid is better, focused or parallel? | focused |
| what are the three factors to consider with grid selection? | kVp, degree of clean-up, patient dose |
Created by:
b.xray