Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

202 MEDIMAGE > 10. Exposure technique factors: Primary and Secondary technique factors > Flashcards

10. Exposure technique factors: Primary and Secondary technique factors Flashcards

1
Q

what are 2 factors that contribute to compton scatter

how

A

kVp = affects beam penetrability

Volume of irradiated material = field size and patient thickness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

increasing the kVp has what effect on transmission

A

increases transmission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

increasing the kVp has what effect on photoelectric scatter

A

decreases photoelectric scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

increasing the kVp has what effect on compton scatter

A

increases compton scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

increasing the kVp has what effect on patient dose

how

A

decreases dose

increase penetrability of beam so less is attenuated in tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

increasing the kVp has what effect on image quality

A

lower amounts of contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

decreasing the kV means what needs to be done for the mAs

A

Decrease in kv is more absorbtion but need to increase mAs to compensate (15% rule to maintain image quality)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does increasing mAs result in for the beam

A

increases number of photons in the beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the 3 factors of the volume of irradiated material

A

field size

patient thickness

average tissues density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

increasing the field size does what to the volume of tissue radiated

what effect does this have on the scatter

A

increases it

increases scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

increasing FS has what effect on the beam quantity

what are the 3 factors causing this

A

increases it

increases scatter and amount of remnant radiation hitting the receptor

can increase image noise without mAs compensation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the field size

A

how big the image is

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the tradeoff when you decrease the field size

what needs to be done to compensate for this trade off

A

fewer photons reach the IR so exposure decreased

increase in mAs must accompany significant reduction in the field size to maintain image exposure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what 2 factors of the nature of body parts produce more scatter

why

A

thicker and denser parts = more scatter

both increase number of interactions x-ray beams undergo as it passes through the body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why do denser body parts produce more scatter

A

higher e- density present in thicker/denser tissues

increased likelihood of interactions occurring especially photoelectric

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

compression devices are used to improve spatial resolution and contrast how

in terms of thickness and dose and OID

A

decrease patient thickness
makes thickness more uniform

lowers patient dose and brings tissue closer to receptor by decreasing the OID

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what are the 3 primary exposure factors

A

mAs

kV

exposure time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what does increasing mAs do to the beam

A

more photons in beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what does increasing the kVp do to the beam

A

increase quantity and quality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

mAs increase has what effect on the quantity of radiation reaching the IR

what is the relationship

A

direct proportional

increases quantity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

mA and exposure time have an ___ ___ relationship when maintaining the mAs

A

inverse proportional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how does kV affect the x-ray beam penetration and absorption in anatomic tissues

A

increase kV increases penetration and decreases absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how does kV affect the subject contrast

A

increasing kVp decreases subject contrast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what does lower kV do to the variation in the x-ray intensities exiting the patient

A

greater variation in the x-ray intensities exiting the patient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is the 15% rule in terms of the IR exposure

what are the equations for increasing and decreasing the exposure and maintaining the exposure

A

to increase exposure to the IR multiply the kVp by 1.15
1.15 x (original kV + 15%)

to decrease the exposure to the IR multiply by 0.85
0.85 x (original kV - 15%)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is the 15% rule in terms of the IR exposure

what are the equations for maintaining the exposure when kVp is increased or decreased

A

to maintain the exposure to IR, when increasing the kVp by 15% (kVp x 1.15), divide the original mAs by 2

when decreasing the kVp by 15% (kVp x 0.85), multiply the mAs by 2

27
Q

is image brightness dependent on mAs and kVp

A

no

28
Q

is image contrast dependent on kVp

A

no

29
Q

what does it mean when people say that digital IRs have a wide dynamic range

A

can use a wide range of exposure factors and still get a good quality range

30
Q

what happens to the exposure and image brightness/contrast if there is too much mAs and/or kV used

A

patient overexposed

computer processing adjust image brightness and contrast

31
Q

what happens to the quantum noise if there is too little mAs and/or kV used

A

it will be visible

32
Q

the screen film comes in different speeds what does it mean when its faster/higher speed

in terms of exposure factors

A

Faster/higher speed = more exposure characters, syst takes the few pixel it has and gives you the info you want

Fast = lower exposure factors

33
Q

what are 10 secondary factors

A

focal spot size

SID

OID

central ray-anatomic part image receptor alignment

Grids

beam restriction

generator output

tube filtration

compensating filters

patient factors

34
Q

what do secondary factors affect

A

don’t affect production of beam directly

affects the radiation but not directly during its production

35
Q

how does the focal spot size affect unsharpness and spatial resolution

A

increasing focal spot size increases unsharpness and decreases spatial resolution

36
Q

what is the penumbra

A

unsharpness/blurring at the edge of the beam

37
Q

what is the size of a small focal spot

A

0.5-0.6mm

38
Q

what is the size of a large focal spot

A

1.0-1.2mm

39
Q

how does SID affect the radiation intensity

A

inverse square law

increasing SID decreases the radiation intensity reaching the IR

40
Q

how does SID affect the size distortion (magnification) and recorded detail/spatial resolution

A

increasing the SID will decrease magnification and increase resolution

41
Q

what is the SID

A

distance between x-ray tube and IR

42
Q

what is the SID and mAs equation

A

mAs1/mAs2 = (SID1)^2/(SID2)^2

43
Q

what is the equation for the radiation intensity and distance

A

I2/I1 = (d1)^2/(d2)^2

44
Q

what is the OID

A

distance between the anatomic part and the IR

45
Q

which 4 things does the OID affect

A

radiation intensity reaching the IR

amount of scatter radiation reaching the IR

magnification

spatial resolution

46
Q

a smaller OID has what effect on magnification

A

less magnification

47
Q

in terms of OID an air gap will have what effect on the radiation intensity reaching the IR and scatter

A

increase OID so decreases intensity and increases scatter

48
Q

increasing the OID ahs what effect on the IR exposure, contrast and magnification and spatial resolution

A

decrease IR exposure

increase contrast and magnification

decrease spatial resolution

49
Q

what is subject contrast

A

the anatomy and the contrast due to difference of structures

eg. anatomy in chest has got many differences of structures (bone, ribs, lungs all diff thicknesses in chest)

50
Q

what is the magnification factor

what is the equation for the MF and SOD and object size

A

MF = SID/SOD

51
Q

what is the equation for the SOD

A

SOD = SID - OID

52
Q

what is the equation for the object size

A

object size = image size/MF

53
Q

as OID increases the image size ___

A

decreases

54
Q

what is the equation for MF, Lim and Lobj

A

MF = Lim/Lobj

Lim = width of image
Lobj = width of object
55
Q

what are the 3 factors of the CR misalignment

A

tube

part

image receptor

56
Q

what is the purpose of the grid

A

limit the amount of scatter radiation that reaches the IR and improves the quality of the radiograph

57
Q

what effect of less scatter or unwanted exposure on the image is to

A

increase the radiograph contrast

58
Q

what does beam restriction do

what is the tradeoff

A

increased collimation = smaller field size = reducees the amount of tissue irradiated and reduces both the scatter radiation produced and the amount of radiation reaching the IR

higher contrast but needs increase in mAs

59
Q

generators with more efficient output require what exposure techniques to produce an image comparable to those of a single phase unit

A

lower exposure techniques

60
Q

how might tube filtration affect the quality of images

how significantly

A

small variations wont have any effect on the quality

61
Q

what are 3 patient factors

A

body habitus

part thickness effects

pathology

62
Q

what 3 things does the part thickness affects

A

beam attenuation

exposure reaching the IR

scatter production and image contrast

63
Q

what does pathology affect

A

increase or decrease kV (penetration)

202 MEDIMAGE (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions