Brainscape's Knowledge GenomeTM

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


See full index

radiology exam 1 > attenuation > Flashcards

attenuation Flashcards

1
Q

primary components of x ray machine

A
  • tube and power supply in tube head; head supported by arm

- control panel to adjust duration, energy, and exposure rate

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

kvp controls

A

how strong beam is

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

mA controls

A

filament heating

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

when do you change kvp and ma

A

for larger or pedo patients

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

high mA and kV means

A

high density

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

mA is

A

quantity of x ray

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

kV is

A

quality of x ray

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

alternating current

A

when flow of electrons move in one direction and then reverse in opposite direction

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

frequency

A

of alternating current cycles/second = 60 Hz

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

voltage

A

electrical pressure pushing electrons thru a wire

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

current (ampere)

A

number of electrons flowing in a wire/second

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

x ray generator

A

supplies electric power to tube

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

low voltage circuit

A
  • heats tungsten filament

- provides electrons by heating the filament to incandescence

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

high voltage circuit

A
  • create flow of electrons bw anode and cathode

- provides potential difference between anode and cathode

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

step up transformer

A

high voltage current (60-120)

creates potential difference between anode and cathode

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

step down trans

A

low voltage current

heats tungsten filament

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

primary functions of autotransformer

A
  • stabilize incoming electricity (voltage)

- adjusts the voltage flowing to the tube head

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

mA controls

A

temperature of filament and size of electron cloud

  • high–> more e- strike target making more xrays
  • low–> fewer e- strike target making fewer x rays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

longer time–>

A

more x rays

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

shorter time–>

A

fewer x rays

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

double exposure time–>

A

2X more radiation

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

in old x rays, only —- were usable

A

60 of alterations

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

modern dental x rays

A

-replace 60 cycle with high f power supply resulting in constant potential bw cathode and anode

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

tube rating

A

-guide the longest exposure time for range of KV and mA without damage

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

duty cycle

A

freq with which successive exposures can be made without overheating the anode

26
Q

quantity

A

number of photons

27
Q

quality

A

energy of photons

28
Q

intensity

A

total energy (quality x quantity) contained in the beam per unit time per unit area

29
Q

how manufacturer controls intensity

A
  • target material

- filtration

30
Q

how practitioner controls intensity

A

kVp
mA
time
source-receptor distance

31
Q

why use tungsten for target

A
  • high atomic number
  • high melting temp
  • large # of electrons
32
Q

filtration

A

reduces intensity of primary x ray beam by selectively absorbing out useless, low energy x rays

33
Q

inherent filtration

A
  • glass wall of tube, oil, aperture window

- not sufficient to meet NCRP standards

34
Q

added filtration

A

thin sheet of aluminum

35
Q

total filtration=

A

added + inherent

36
Q

influence of filtration

A
  • mean photon energy increases
  • total number of photons decrease
  • most photons removed are lower energy photons
  • helps reduce harmful effects of radiation
37
Q

50-70 kVp –>

A

1.5 mm Al

38
Q

above 70 kVp–>

A

2.5 mm Al

39
Q

what happens if you double the mA

A

twice as many electrons will be released but mean energy doesn’t change

40
Q

the longer the exposure time, the —-

A

more x rays are produced

41
Q

exposure time affects the —, not the —- of the beam

A

affects the quantity not the quality

42
Q

increasing kVp–>

A

increases number of x rays produced (quantity) and also increases energy of beam (quality)

43
Q

15 kVp increase

A

increases intensity by 2X

44
Q

15 kVp decrease

A

decreases intensity by 1/2 or 50%

45
Q

half value layer

A
  • expresses quality of beam

- thickness of an absorbing material necessary to reduce the x ray intensity to 1/2 of its original intensity

46
Q

what are allowed to exit the tube housing

A

only useful, primary beam xrays

47
Q

the intensity —- as distance from the focal spot —-

A

intensity decreases as distance from focal spot increases

48
Q

inverse square law

A

intensity of radiation varies inversely as square of the source-film distance

49
Q

change from 8 to 16 BID – whats the intensity

A

(distance doubled)

1/(2^2)=1/4 original intensity

50
Q

three interactions bw patient and x ray

A
  • photons scattered
  • photons absorbed
  • photons pass completely thru patient
51
Q

coherent scattering

A

incoming photon interacts with atom and sets it in motion and then disappears

  • low energy photon
  • interacts with whole atom & incident photon ceases to exist
  • excited atom returns to stable state and generates another photon
  • secondary photon has same energy as incident photon
  • minimal contribution to film fog
52
Q

compton scattering

A
  • x ray interacts with outer shell e- in pt’s tissue
  • electron ejected
  • scattered photons and e continue and interact
  • photons travel in all directions and cause image degradation/film fog
53
Q

photoelectric absorption

A
  • incident x ray has more energy than binding energy of k shell e- in tissue
  • incident x ray completely disappears
  • photoelectron is generated (ejected from atom)
54
Q

no interaction =

A

black/radiolucent

55
Q

scattering=

A

hazy (fog)

56
Q

absorption=

A

radiopaque (white and gray)

57
Q

factors influencing absorption

A
  1. photon energy (kVp)
  2. thickness of structure
  3. density of structure
  4. atomic number
58
Q

higher kVp results in

A

shorter wavelengths

  • increased energy –> greater penetration of radiation
  • higher energy–> less absorption
59
Q

the thicker the structre, the greater—

A

the amount of absorption

60
Q

density of tissues

A

compactness of material

  • mass/volume
  • greater density–> greater absorption
61
Q

atomic number’s effect on absorption

A

more effect than density or thickness

  • increased probability of interactions
  • greater atomic number–> greater absorption
62
Q

differential absorption

A

different tissues absorb x rays in varying degrees

radiology exam 1 (7 decks)

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