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x-posure/scatter

x-posure/scatter/scatter

QuestionAnswer
remnant x-rays are those that? exit the patient
what factor(s) that affects scatter radiation can be controlled by the technologist? field size
as kVp increases, scatter _______ increases b/c there is less compton interaction
what percent of x-rays are transmitted through a patient? 1%
at a high kVp (125kVp), most x-rays are? TRANSMITTED THRU THE BODY WITH INTERACTION or TRANSMITTED THRU THE BODY WITHOUT INTERACTION transmitted thru the body with interaction
increasing kVp while decreasing mAs decreases what? patient dose
if a constant optical density is maintained while kVp in increased what happens to patient dose? decreases
as field size increases, what happens to scatter? increases
scatter radiation reduces radiographic quality by changing? CONTRAST, DISTORTION, OPTICAL DENSITY, MASS DENSITY contrast
x-rays that the tech would like to have interact with the IR are those that are? transmitted in the body
an increase of kVp from 70 to 80? RESOLUTION IMPROVED, SID MUST BE INCREASED, HIGHER PROPORTION OF SCATTER, LOWER PROPORTION OF SCATTER higher proportion of scatter
an increase in kVp from 70 to 90, while other factors remain constant result in? INCREASED DETAIL, DECREASED # OF ABSORBED RAYS, INCREASED # OF ABSORBED RAYS # of absorbed rays decreases
what increases as the field size of the beam increases? QUANTUM MOTTLE, SCATTER, MAGNIFICATION scatter
as thickness of the anatomy increases what factor increases? mAs, kVp, SID, OID kVp
which process is most responsible for the production of scatter? PHOTOELECTRIC EFFECT, COMPTON EFFECT, TRANSMISSION compton effect
which is not a beam-restricting device? CONE, APERTURE DIAPHRAGM, PBL, ADDED FILTRATION added filtration
an aperture diaphragm allows x-rays to expose an area? a size just smaller than the IR
when an aperture diaphragm is used cutoff can occur when? the diaphragm is not properly positioned
which is the most simple of all beam-restricting devices? CONE, ALUMINUM FILTER, APERTURE DIAPHRAGM aperture diaphragm
off focus radiation occurs when? projectile electrons do not strike the focal spot
cones and cylinders are used primarily to reduce? scatter
a decrease in field size will result in? decrease in radiographic density, decrease in scatter within the patient
factors that influence scatter in image forming beam? kVp, field size, pt thickness
TRUE OR FALSE soft tissue absorbs more radiation and produces more scatter than bone? false
what is the purpose of bean limiting devices? control scatter
principle reason for using a grid? improve image contrast
which material is the most radiolucent? ALUMINUM, CARBON FIBER, COPPER, LEAD carbon fiber
what is the most important grid characteristic? grid ratio
if only scatter reached the IR the image contrast would be? very low
grids are principally effective in attenuating which of the following? photoelectrons, remnant radiation, x-rays after compton interaction, x-rays after photelectric interactions x-rays after compton interaction
if the interspace dimension is constant, increasing the grid ratio will? make the grid thicker
as grid frequency increases what happens with the grid strips? # of strips/cm increases and interspace width becomes thinner
use of which will reduce radiographic contrast? COLLIMATORS, FILTRATION, GRIDS, INTENSIFYING SCREENS filtration
which is the best grid material in terms of x-ray attenuation? COPPER, IODINE, TUNGSTEN, URANIUM uranium
which will not improve image contrast? DECREASE KvP, GRID, ADDED FILTRATION, COLLIMATING DOWN added filtration
which are more effective, high grid ratios or low grid ratios? high grid ratios
efficiency of a grid to reduce scatter is related to? GRID FREQUENCY, GRID INTERSPACE, GRID RATIO grid ratio
which is the least important indicator of grid performance? GIRD FREQUENCY, GRID MASS, GRID STRIP HEIGHT, GRID RATIO grid strip height
the contrast improvement factor is defined as the x-ray contrast obtained ______ with a grid compared to that obtained without a grid
in general, the selectivity of a grid depends on which? CONTRAST IMPROVEMENT FACTOR, FOCAL LENGTH, GRID FREQUENCY, GRID MASS, GRID RATIO grid mass
x-ray grids with high contrast improvement usually effects resolution by? improving contrast resolution
which is the simplest type of grid? CROSSED GRID, FOCUSED GRID, LINEAR GRID, linear grid
undesirable absorption of image-forming x-rays by a grid is called? grid cutoff
one factor that does not affect the percentage of scatter that reaches the IR? GRID MASS, GRID RATIO, kVp, mAs, PATIENT THICKNES mAs
which of the following would reduce production of scatter? DECREASE IN FIELD SIZE, DECREASE IN SID, DECREASE IN OID, FILTER, GRID decrease in field size
what kind of grid reduces scatter along two axes? crossed grid
what is a disadvantage of a moving grid? may produce blur
when the air-gap technique is used, what happens to resolution? contrast resolution is improved
when the air-gap technique is used, what happens to patient dose? increased patient dose
what happens if you replace an 8:1 grid with a 12:1 grid? greater positioning latitude
which has the greatest contrast improvement factor? CROSSED GRID, FOCUSED GRID, MOVING GRID, PARALLEL GRID crossed grid
scatter photons increase contrast? TRUE OR FALSE false
as irradiated tissue volume increases, scatter increases? TRUE OR FALSE true
if the height of the grid is constant and distance is decreased between the lead strips there would be an increase in grid ratio? TRUE OR FALSE true
cross-lateral grids are commonly used in clinical practice? TRUE OR FALSE false
a focus design results in a grid with strips designed to match the divergence of the x-ray beam? TRUE OR FALSE true
if the x-ray tube is not centered on the central axis of the focus grid, it is termed lateral re-centering? TRUE OR FALSE true
off focus errors result in grid cut off along the peripheral edges of the IR? TRUE OR FALSE true
utilizing the air-gap technique will increase the amount of scatter reaching the radiograph itself? TRUE OR FALSE false
what is known as the degree of difference of optical density between areas of the image? contrast
contrast on a radiographic image is highest when the amount of __________ scatter is the lowest compton
grids remove scatter before the beam reaches the ________ IR
amount of grid scatter depends on what 3 factors? 1-angle of scattered photons 2-height of grid strips 3-width of grid strips
what is the grid ratio? height/distance
a grid with good clean-up will remove what percent of scatter? 80-90%
grid frequency is how many lines/inch? 60/110
pt dose and technical factors increase proportionally with the _________ factor bucky
main disadvantage of using a parallel grid? grid cut off
with tech factors over 90 kVp, it is best to sue grids with what ratios? 8:1
photons that pass through the body unaffected produce? radiographic contrast
photon absorption within the body results from? photelectic interactions
a grid is made of thin __________ ______ strips and ___________ fillers that are aligned with the beam radiopaque lead, radiolucent
which grid would have the greatest distance between strips? 6:1
the purpose of a moving grid? to blur grid lines
amount of scatter increases with what 3 things? increase in pt thickness, increase in field size, decrease in atomic #
as kVp increases, contrast _________, scatter _______ and IR exposure _________ contrast decreases, scatter increases, IR exposure increases
angulation of the long axis of a linear grid will cause? grid cut off
amount of scatter radiation is affected by? collimation and kVp
grid cut off and off centering results in ______ of density loss
grid cut off is more pronounced with high- ratio grids or low-ratio grids? high-ratio grids
what is the result of replacing an 8:1 grid with a 12:1 grid? greater positioning latitude
besides an exam needed a wide rang SID, which grid would most likely produce grid cut off? 5:1 6:1 8:1 12:1 16:1 16:1
when the air gap technique is used, what happens to contrast resolution? improves
Created by: srehrauer
 

 



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