Ouhsc Radiographic Principles Test 3

Front 1

scatter radiation produced by what type of interaction?

Back 1

compton interaction

Front 2

compton interactions.....

Back 2

are of NO USE in demonstrating the structures of interest.

Front 3

scatter radiation reaching the film will increase/decrease the radiographic density??

Back 3

increase (without improving the diagnostic value of the information)

Front 4

scatter radiation will reduce/improve the contrast of the radiographic image?

Back 4

reduce (adds more shades of grey)

Front 5

relationship between scatter and radiographic density? direct or indirect?

Back 5

direct (more scatter = more density)

Front 6

scatter related to contrast?? direct or indirect?

Back 6

indirectly proportional

more scatter = low contrast (more grays)

less scatter = high contrast (more b&w)

Front 7

increasing the kV will increase/decrease the penetrating ability of the x-ray photons??

Back 7

increase

Front 8

if no other technical factor is changed other than kV what happens to the overall density of the radiograph?

Back 8

it will increase since more of the photons are exiting the patient and striking the film

Front 9

increasing kV will increase/decrease the penetrating ability of the beam?

Back 9

increase

Front 10

increasing kV causes an increasing number of what occurring within the patient??

Back 10

compton interactions

(this increases the amount of scatter)

Front 11

Increase in kV will cause the number of photoelectric absorptions to increase/decrease?

Back 11

decrease

Front 12

A decrease in PE absorptions will increase/decrease the patient dose?

Back 12

decrease

Front 13

increasing kVp and reducing mAs will ??

Back 13

increase beam penetrability

maintain radiographic density

increase compton interactions causing more scatter

reduce image quality

Front 14

in irradiated material, as tissue volume increases the amount of scatter radiation increases/decreases??

Back 14

increases

Front 15

high atomic # materials include:

Back 15

iodine, barium, and lead

Front 16

the higher the atomic # of the material stuck by the x-ray photon....

Back 16

the more PE interactions... therefore reduce the amount of compton interactions (scatter)

Front 17

when using beam restrictions the number of x-ray photons reaching the patient will increase/decrease?

Back 17

decrease

Front 18

When using beam restriction, the need for an increase/decrease of technical factors?

Back 18

increase technical factors to compensate for overall reduction in x-ray photons

Front 19

three types of beam restrictors

Back 19

aperture diaphragms

cones/cylinders

collimators

Front 20

aperture diaphragm

Back 20

the simplest type of beam-restricting device

flat piece of metal (lead) with an opening to allow radiation to pass through

Front 21

what shape is the opening of an aperture diaphragm?

Back 21

the opening can be any shape. However, once it is cut, you can not re cut it.

Front 22

where is the aperture diaphragm located?

Back 22

placed on the bottom of the collimator or taped directly to the tube housing

Front 23

what is an advantage of an aperture diaphragm?

Back 23

they are inexpensive

Front 24

what type of machines is the aperture diaphragm used on?

Back 24

mammo machines. not used with modern diagnostic machines

Front 25

cones/cylinders

Back 25

circular aperture diaphragm with metal extensions.

cones flared at the end

cylinders are constant in diameter

Front 26

with adjustable cylinders, as cylinder length increases the amount of radiation reaching the patient and film increases/decreases??

Back 26

decreases

Front 27

where are cylinders located??

Back 27

they attach beneath and on the outside of the tube housing.

Front 28

increasing cylinder length will do what to the field size?

Back 28

decrease the field size

Front 29

how do you determine the cone field size??

Back 29

projected image size = SID x lower diameter of cone/ distance from focal spot to bottom of cone

Front 30

using a 3" cylinder, 40" SID, the bottom of the cylinder is 12" below the focal spot. How big will the approximate field size be?

Back 30

40" x 3" / 12

120"/12

projected image size = 10" circle

Front 31

what is the most frequently used method of beam restriction?

Back 31

collimators

Front 32

collimators

Back 32

contain two sets of lead shutters to absorb radiation.

knobs to control the longitudinal and horizontal fields.

Front 33

bottom set of shutters

Back 33

reduce penumbra along the periphery of the beam

Front 34

upper shutters

Back 34

prevent most of the off focus radiation from reaching the film

Front 35

what is the purpose of the mirror?

Back 35

acts as a filter and absorbs low energy x-rays.

simulates the path of the x-ray photons

Front 36

alignment accuracy of the light source and x-ray beam can be checked by???

Back 36

doing a collimator test

Front 37

acceptable limits are determined by??

Back 37

the department quality standards

Front 38

What is the U.S. Federal Standard?

Back 38

2% SID error

Front 39

Automatic Collimators also called ???

Back 39

Positive Beam Limitation (PBL) device

Front 40

automatic collimators/PBL

Back 40

will adjust the dimension of the x-ray beam to the image receptor placed within the bucky

Front 41

ancillary devices

Back 41

lead blockers

lead masks cut to a specific shape or size

Front 42

purpose of the grid

Back 42

used to improve the contrast of the image by absorbing the patient generated scatter radiation before it can strike the image receptor

Front 43

scatter creates _________ density on the image which reduces contrast?

Back 43

inaccurate

Front 44

grids are located __________ the patient and ________ the image receptor?

Back 44

after patient

before image receptor

Front 45

grids are used on what size body parts?

Back 45

thick

10 cm or larger

Front 46

grids are used on procedures utilizing what type of kVp settings?

Back 46

high

70 kVp or higher

Front 47

Grid Construction

Back 47

flat device

radiolucent material separating thin, vertical radiopaque strips.

Front 48

The vertical strips are made of what?

designed to do what?

Back 48

made of lead

designed to absorb scatter radiation

Front 49

what are the radiolucent interspace materials designed to do?

Back 49

Allow the remnant photons to strike the film

Front 50

Rectangular grids, strip orientation

Back 50

strips running with the long axis of the rectangle

Front 51

Grid ratio is

Back 51

The relationship of the HEIGHT of the lead strips to the DISTANCE BETWEEN the strips.

Front 52

grid ratio equation

Back 52

grid ratio = h/D

Front 53

a/an _____________ relationship exists between the distance between the lead strips and grid ratio when the height of the grid strips remains the same.

Back 53

inverse

Front 54

which grid ratio stops scatter radiation better

Back 54

high grid ratio

Front 55

which grid ratio results in higher contrast images?

Back 55

high grid ratios

Front 56

Which require a higher adjustment in the radiographic technique to maintain the density of a non-grid technique?

Back 56

high grid ratios

Front 57

Grid Frequency

Back 57

The number of vertical strips per unit of grid width

Front 58

as the frequency per unit of distance increases the vertical strips...

Back 58

will be thinner

Front 59

grid patterns

Back 59

linear

cross hatched

Front 60

linear

Back 60

parallel strips of lead allows tube angulation if parallel with the lead strips

Front 61

Cross-hatched

Back 61

tow linear patterns criss-crossed

more efficient at removing scatter radiation

no tube angulation

Front 62

Focused Grids

Back 62

linear positioned lead strips

angled similar to the angulation of the primary beam as it diverges

has a point of convergence similar to the primary beam

Front 63

focused grids require proper SID to be efficient at reducing ______ and simultaneously allowing the remnant x-ray photons to pass.

Back 63

scatter

Front 64

what is extremely important when using focused grids?

Back 64

focal range is extremely important!!

Front 65

latitude

Back 65

freedom from the usually restraints, limitations, or regulations.

Front 66

high latitude

Back 66

larger allowable changes (forgiving)

fewer restraints

Front 67

grid latitude

Back 67

amount you can be off and still get an acceptable x-ray

Front 68

as grid ratio increases the need for proper SID _________. increases/decreases

Back 68

increases

Front 69

As grid ratio increases the latitude for SID _____________. increases/decreases

Back 69

decreases

Front 70

In high grid ratios small error in SID can cause....

Back 70

a large amount of grid cutoff

Front 71

Low grid ratios have a ______ latitude regarding SID

Back 71

High

Front 72

low grid ratios regarding SID error

Back 72

small or large errors may not cause much grid cutoff

Front 73

grid cut off

Back 73

improper alignment of the grid will reduce the amount of remnant radiation from striking the image receptor.

Front 74

permanent grid location

Back 74

located within the potter-bucky diaphragm, above the image receptor location

Front 75

permanent grid lines

Back 75

will be parallel with the table length, or vertical direction of the wall bucky

Front 76

portable grids

Back 76

can be encased within a plastic holder into which the cassette is inserted

can be taped to an existing cassette

can be a permanent part of the cassette construction

Front 77

Relationship of grids and radiographic density

Back 77

as grid ratio or frequency increases the radiographic density decreases

Front 78

To avoid Moire artifacts grid frequency for digital imaging should be higher than

Back 78

80 lpi

(bucky device should also be used whenever possible)

Front 79

increasing grid efficiency will

Back 79

decrease radiographic density by reducing the number of x-ray photons striking the image receptor

Front 80

relationships of grids and radiographic contrast

Back 80

as grid ratio or frequency increases the radiographic contrast increases.

Front 81

Increasing grid efficiency will

Back 81

increase (create high) radiographic contrast

-by reducing the number of different energies of x-ray photons striking the image receptor.

Front 82

Grid cost

Back 82

increases with effectiveness

increases with cassette size

they are hundreds of dollars

Front 83

which are used more frequently, focused or parallel grids???

Back 83

focused

Front 84

grid conversions factors

Back 84

constants used to determine the change in technical factors needed for specific grid ratios.

Front 85

Because grids attenuate remnant primary beam, what must be adjusted when changing grid ratio?

Back 85

mAs

Front 86

To maintain density as grid ratio increases mAs must

Back 86

increase to offset the number of photons being attenuated by the grid

Front 87

Grid Conversions Factors

Back 87

see slide for equation and mAs increase

Front 88

increasing the grid ratio will _________ the amount of scatter radiation and the radiographic density if the mAs is not increased to maintain density

Back 88

decrease

Front 89

types of grid errors

Back 89

off level

off center

off focus

upside down

Front 90

off level grid error

Back 90

occurs when the tube is angled across the long axis of the grid strips OR the grid is unleveled in comparison to the tube

**portable grids

Front 91

off level grid appearance

Back 91

decrease in density across the entire image

Front 92

off center grid errors

Back 92

x-ray tube is not centered with the center of the focused grid.

**fixed or portable grids

Front 93

off center grid errors appearance

Back 93

decrease in density across the entire image. The greater the lateral off-centering, the greater the grid cut-off.

Front 94

off focus grid errors

Back 94

SID outside the acceptable range of the focused grid

**fixed or portable grids

Front 95

off focus grid appearance

Back 95

decrease in density at the lateral margins of image

Front 96

upside down grid error

Back 96

center of the grid will allow the x-ray beam to pass unrestricted flipped upside down or not

Front 97

upside down grid appearance

Back 97

severe decrease in density at the lateral margins of image

Front 98

other scatter reduction methods

Back 98

collimating is still necessary with the use of grids

air gap technique

reverse cassette technique

Front 99

air gap technique

Back 99

alternate method to the use of grid

large OID

the amount of scatter will stay consistent however the amount reaching the image receptor will be reduce with OID

Front 100

Reverse- Cassette technique

Back 100

flip the cassette so the remnant radiation strikes the back side of the cassette first

lead foil on the back side of the intensifying screen to prevent backscatter

foil acts as a filter stopping compton radiaton

must increase mAs to maintain density

Front 101

increasing grid ratio will ____________ radiographic density.

Back 101

decrease

Front 102

High grid ratio compared to low grid ratio

Back 102

high grid ratios have a narrow latitude conceding SID and alignment

High grid ratios have a larger GCF

Front 103

Grids do not CREATE ________

they ABSORB ___________

Back 103

SCATTER

Front 104

What creates scatter?

Back 104

The patient