Brainscape's Knowledge GenomeTM

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


See full index

image production and evaluation Semester 2 > test 1 > Flashcards

test 1 Flashcards

1
Q

Anode Heel Effect

A

xrays are more intense on the cathode side of the tube. Intensity of xrays decreases toward the anode side. as xrays are emitted from anode some are absorbed by anode due to heel of target. More xrays are emitted toward the cathode. The cathode side gets put over thicker body part resulting in more even density.

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

line focus principle

A

the relationship between the actual focal spot and the effective focal spot.
shows that by angling the face of the anode, the actual focal spot can remain large while effective focal spot is reduced in size.
greater heat capacity with good image quality

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

what causes the anode to crack?

A

high techniques applied to cold anode.
temp increases too rapidly and the anode cracks.
be sure to warm up the tube

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

what causes pitting?

A

excessive heat placed onto the anode.

causes surface melting and pitting of the target

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

Why is tungsten used for filament and anode?

A

used because it has a high melting point, high atomic # (makes it more efficient in producing electrons), thermal conductivity for efficient xray production, and can withstand high tube currents without cracking or pitting.

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

extra focal radiation

A

xrays produced from outside the focal spot. is undesirable and increases the patient dose and creates unwanted density

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

off focus radiation

A

most off focus radiation is attenuated/weakened by tube housing and collimator located near window of glass housing

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

what is oil used for?

A

oil acts as an insulator to help dissipate the heat

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

brehms xrays

A

produced when a projectile electron passes by nucleus, slows down, and changes its course. it leaves with reduced kinetic energy. the loss of energy reappears as an xray. the more angle on the target, the more energy the electron has/gives off.

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

characteristic radiation

A

created when a projectile electron knocks out an inner k-shell electron so the next shell electron drops in.
have very low energy

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

characteristic cascade

A

outer shell electron leaves a hole, and another electron fills in and so on.

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

kinetic energy becomes what when it hits the target?

A

thermal energy and electromagnetic energy

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

4 factors of xray production

A
  1. separation of electrons
  2. production of high speed electrons
  3. focusing of electrons
  4. stopping high speed electrons in target
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q
  1. separation of electrons
A

ex: thermionic emission

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q
  1. production of high speed electrons
A 
apply the kV and the kV causes electrons to travel at high speed from cathode to anode.
# of electrons is created by how much mA
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
  1. focusing of electrons
A 
focal spot (anode)
focusing cup (cathode)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q
  1. stopping high speed electrons in target
A

electrons hit target, transfer kinetic energy to target, electrons slow and almost stop, electrons interfere with orbital electrons which results in conversion of kinetic energy to thermal and electromagnetic energy. 98% heat 2% electromagnetic energy

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

leakage radiation must be reduced to?

A

less than 100mR/hr at 1m

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

space charge

A

electrons come off from the filament during thermionic emission that form a cloud around the filament

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

space charge effect

A

the cloud of electrons not allowing more electrons to be boiled off the filament

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

thermionic emission

A

when outer shell electrons are boiled off and ejected from filament

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

focusing cup

A

filament embedded in cup
allows electrons to flow freely across the tube from cathode to anode
focuses the electrons to a small area on the anode.
made of nickel/molybdenum

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

anode

A 
positively charged electrode 
has 2 types 
1. stationary 
2. rotating 
consists of target, stator and rotor.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

target

A

embedded in molybdenum and graphite.

angled for xrays to exit the tube.

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

heat is dissipated in what 3 ways

A
  1. convection
  2. conduction
  3. radiation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q
  1. convection
A

fan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q
  1. conduction
A

stem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q
  1. anode
A

emits infrared energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

protective housing

A

metal tube housing

protects against accidental shock

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

glass envelope

A

provides insulation from electrical shock

dissipates heat in tube by using oil

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

housing window

A

section where xrays are emitted/ exit the tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

cathode

A

negative side of the tube
consists of 2 parts
1. filament
2. focusing cup

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

filament

A

very small.
emits electrons when heated
located in the focusing cup
smaller filament can’t withstand too much heat used for smaller body part to get better detail use less mAs
larger filament used for larger body parts. more mAs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Single phase heat unit

A

HU= kVp x mA x s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

High frequency 3 phase 12 pulse

A

HU = 1.4 x kVp x mA x S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

3 phase 6 pulse

A

HU = 1.35 x kVp x mA x S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Tube rating chart

A

Exposure factors lying under the curve Are Safe

38
Q

1 heat unit

A

HU= kVp x mA x time

39
Q

the heel effect:

a. exists because some xrays are absorbed by the surface of the anode
b. is caused by the charge difference between the anode and the cathode
c. depends on the mA and kVp
d. is reduced by dual focal spots

A

a.

40
Q

the purpose of the cathode focusing cup is to

a. alter the filament size
b. group the electrons for their passage to the anode
c. regulate anode rotation speed
d. increase the heat capacity of the tube

A

b.

41
Q

a molybdenum shaft is used to connect the anode to the rotor because :

a. it is a less dense metal with a high melting point
b. it is easily compressed
c. it has a high inertia
d. it produces 17.5 keV xrays

A

a.

42
Q

many xray tubes have 2 filaments:

a. because the second filament can be used as a spare when the first burns out
b. to provide 2 focal spots
c. to allow cooling of the filament by alternating exposures
d. to improve tube cooling by sharing the heat between 2 filaments

A

c.

43
Q

a technologist can control the quantity of the xrays striking the patient by adjusting the:

a. mA
b. kvp
c. rectification
d. anode material

A

a.

44
Q

T or F: an increase in focal spot size will increase the heat capacity of the tube

A

True

45
Q

T or F: an increase in anode rotation speed will increase te heat capacity of the tube

A

True

46
Q

T or F: an increase in target angle will increase the heat capacity of the tube

A

False

47
Q

T or F: the effective focal spot will increase with an increase in the anode angle

A

True

48
Q

T or F: the effective focal spot will increase with an increase to the anode rotation speed

A

False

49
Q

The effective focal spot will increase when changing from 100 to 400 mA

A

True

50
Q

the transfer of heat by ___________ is increased by mounting a fan on the tube housing

a. convection
b. conduction
c. radiation
d. convention

A

a.

51
Q

the heel effect is more pronounced

a. with smaller SID
b. with a large focal spot
c. with a large target angle
d. with a higher speed anode rotation

A

a.

52
Q

the disadvantage of a small target angle is

a. insufficient heat capacity
b. greater field coverage
c. a greater anode heel effect
d. more uniform radiographic density

A

c.

53
Q

thermionic emission is the emission of

a. thermions
b. electrons from a heated cathode
c. electron from a heated anode
d. xrays from the tube housing

A

b.

54
Q

the tube current (mA) is changed by changing the

a. filament current
b. anode voltage
c. focal spot size
d. exposure time

A

a.

55
Q

to extend xray tube life the technologist should

  1. perform warm up exposures at the beginning of each day
  2. extend the time that the boost current button is held down
  3. avoid repeated exposures at or near the tubes capacity
    a. 1 and 2
    b. 1 and 3
    c. 2 and 3
    d. 1 2 and 3
A

b.

56
Q

which chart should be consulted to ensure that adequate time has passed before making an additional exposure

a. a tube rating chart
b. an anode cooling curve
c. a heat unit index

A

b.

57
Q

characteristic radiation is produced when

a. electrons are stopped at the cathode
b. a vacancy in an electron orbit is filled
c. a vacancy in the nucleus is filled
d. electrons are stopped at the anode

A

b.

58
Q

xray tube filtrations filter out

a. low energy electrons
b. high energy electrons
c. low energy xrays
d. high energy xrays

A

c.

59
Q

as kVp is increased, the production of xrays

a. decreases
b. increases
c. remains the same

A

b.

60
Q

what are the 4 factors affecting xray quantity

A
  1. mAS
  2. kVp
  3. distance
  4. filtration
61
Q

less mA =

A

lighter image

62
Q

more mA =

A

darker image

63
Q

longer the exposure time =

A

darker image

64
Q

shorter exposure time =

A

lighter image

65
Q

Inverse square law

A

when the distance is doubled the same radiation is spread over an area 4 times as great

i1 = _ (d2)squared_
i2 (d1) squared

66
Q

as SID decreases density…

A

increases

67
Q

as SID increases density…

A

decreases

68
Q

Direct square law density maintenance

A

when the SID is increased the mAs must be increased by SID squared to maintain constant optical density

mAs1 = (d1)squared (SID)
mAs2 (d2)squared(SID

69
Q

Xray quality =

A

kVP = penetrating power

70
Q

Xray quantity =

A

mAs

71
Q

high kVp =

A

more gray low contrast

72
Q

low kVp =

A

black and white high contrast

73
Q

15% rule

A

a 15% increase in kVp will have the same effect on the optimal density as doubling the mAs
a 15% decrease in kVp will have the same effect on the optimal density as decreasing the mAs by half

10 mAs @ 92kVp will be twice as dark as 10 mAs W@80 kVp
because 92kV is 15% more than 80kV

74
Q

to increase density

A

multiply the kVp by 1.15

makes image twice as dark

75
Q

to decrease density

A

multiply the kVp by 0.85

makes image half as dark

76
Q

Maintaining density

A

if you’re increasing kVp by 15% divide the original mAs by 2
if you’re decreasing kVp by 15% multiply the mAs by 2

77
Q

filter

A

any material to effectively absorb photons from the xray beam

78
Q

what is the most common filtering material

A

Aluminum because its readily available, inexpensive and easily shaped

79
Q

other filters include

A

copper, tin, gadolnium

80
Q

Inherent filtration

A

filtration in the path of the xray beam

within the tube, the oil, and glass envelope

81
Q

added filtration

A

filtration added to port of xray tube. positioned between the tube housing and the xray beam collimator

82
Q

total filtration

A

added filtration + inherent filtration

83
Q

minimum filtration is

A

2.5 mm of Aluminum or equivalent

84
Q

half value layer

A

the amount of filtration needed to reduce the intensity of xray beam to one half its original value
HVL evaluates the tube efficiency

85
Q

beam attenuation

A

the reduction in xray intensity due to xray absorption and scattering
occurs as a result of photon interactions with atomic structures

86
Q

differential absorption

A

process whereby some of the xray beam is absorbed in the tissue and some passes through anatomy

87
Q

backscatter

A

occurs when a scattered photon travels back in the direction of the incident photon or beam
happens in larger patients or with higher kVp

88
Q

transmission

A

xray photon passing through anatomic part without any interaction with the atomic structures
lower kV =less xray transmission
higher kV = more transmission

89
Q

exit radiation

A

remaining xray beam leaving the patient

also known as remnant

90
Q

fog

A

unwanted density created from scatter

obscures small details

image production and evaluation Semester 2 (4 decks)

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