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CORE > Physics Ch 1 XR Production > Flashcards

Physics Ch 1 XR Production Flashcards

1
Q

Atom:

A
X
Z

what is A? Z?

A 
A = mass
Z = atomic #
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2
Q

differentiate: hard vs soft xrays

A

hard: high energy xray –> diagnostic images
soft: low energy xray –> can’t make images –> but add to rad dose to pt

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3
Q

differentiate: xray vs gamma ray –> origin?

A

electron –> xray

nucleus –> gamma ray

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4
Q

what is alpha particle?

A

2 proton + 2 neutron

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5
Q

what subst are ionizing? (4)

A
  • xray
  • gamma ray
  • alpha particle
  • beta particle
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6
Q

alpha particle –> ionization –> MOA?

A

alpha particle –> +2 charge –> attract electrons off nearby atoms –> atoms become ionized

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7
Q

alpha particle –> what is their use?

A

tx (not imaging)

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8
Q

alpha particle:

  • travel distance?
  • penetration?
A
  • travel short distance

- can’t penetrate far

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9
Q

what is beta particle?

A

electron emitted from nucleus

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10
Q

beta particle:

  • travel distance?
  • penetration?
A
  • travel far

- penetrate deep

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11
Q

xray production –> quick overview?

A

tungsten filamt (cathode) –> heated –> release free electrons –> accel to tungsten target (anode) –> electrons strike target –> release energy –> excitation, ionization, radiative loss (Bremsstrahlung)

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12
Q

envelope (glass tube around anode & cathode) –> purpose? why?

A

vacuum

not want free electrons to collide w gas molecules

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13
Q

what is milliAmpere (mA)?

A

electrons mv from cathode to anode –> current

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14
Q

XR production device –> focusing cup –> purpose?

A

reduce spatial spreading –> free electrons –> collect them into a focal spot –> more focused electron beam –> strike target in an acceptable size

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15
Q

XR production device –> rotating anode –> purpose?

A

free electrons –> strike target (anode) –> produce high heat –> anode rotate –> spread heat over larger surface area –> prevent anode from melting

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16
Q

XR production device –> what is focal spot?

A

anode target –> spot where electrons strike

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17
Q

XR production device –> angled anode –> purpose?

A

increase surface area to disperse heat

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18
Q

XR production device –> angled anode –> what is apparaent (effective) focal spto?

A

spot where xrays strike pt

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19
Q

mammo –> focal spot –> size?

A
  • 0.1 mm

- 0.3 mm

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20
Q

gen xr –> focal spot –> size?

A
  • 0.6 mm

- 1.2 mm

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21
Q

portable xr device –> anode –> stationary or rotating or angled?

A

stationary

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22
Q

XR production device –> angled anode –> smaller angle –> what happens to effective focal spot?

A

smaller angle –> smaller effective focal spot

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23
Q

XR production device –> angled anode –> angle too small –> what happens to xray beam?

A

xray beam too small –> can’t travel typical 40” source-to-image distance –> no image

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24
Q

XR production device –> angled anode –> smaller angle –> what happens to heel effect?

A

smaller angle –> greater heel effect

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25
Q

what is heel effect?

A

free electrons –> strike angled anode –> xray created –> xray must travel out of anode material –> smaller/steeper angle –> increase distance xray must travel –> lose energy (more attenuated) –> broader spectrum of different xray intensities (greater differential xray attenuation)

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26
Q

XR production device –> angled anode –> heel effect –> side closer to the cathode –> xray beam is stronger or weaker?

A

cathode side –> more intense beam

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27
Q

XR production device –> angled anode –> lrger focus to film distance (FFD) –> what happens to heel effect?

A

inc FFD –> less variation in xray beam that hits the film –> dec heel effect

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28
Q

XR production device –> angled anode –> smaller film (field of view) –> what happens to heel effect?

A

smaller film –> less variation in xray beam that hits the film –> dec heel effect

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29
Q

XR –> thoracic spine –> proper cathode position?

A

abd aspect

30
Q

XR –> femur –> proper cathode position?

A

proximal aspect

31
Q

XR –> tib/fib –> proper cathode position?

A

prox aspect

32
Q

XR –> humerus –> proper cathode position?

A

prox aspect

33
Q

XR –> forearm –> proper cathode position?

A

prox aspect

34
Q

pediatric –> XR –> femur –> proper cathode position? why?

A

distal aspect

reduce xray exposure to gonads

35
Q

XR production device –> filter –> purpose?

A

block low energy xray (soft xray)

36
Q

xray tube –> operates over 70kVp –> what is minimum filtration required?

A

2.5mm

37
Q

differentiate: keV vs kVp? relationship?

A

keV: beam –> randomly chosen single electron –> its energy

kVp: beam –> electrons as a whole –> max speed/energy some electrons can have

kVp = max keV

38
Q

higher atomic number –> more or less Bremsstrahlung?

A

larger atom –> more Brems

39
Q

90-yttrium –> B-emitter –> what should use as shield –> plastic vs lead? why?

A

plastic –> lower atomic number –> less Brems production

40
Q

tungsten –> K-shell –> binding energy?

A

-69.5 keV

41
Q

xray tube –> set to 80-150 kVp –> what % of the xrays produced will be K-shell characteristic XR?

A

10-25%

42
Q

xray tube –> set very high kVp (>300) –> what % of the xrays produced will be K-shell characteristic XR?

A

negligible %

43
Q

xray tube –> set to 69.0 kVp –> what % of the xrays produced will be K-shell characteristic XR?

A

0%

44
Q

what is beam intensity? unit?

A

(#xrays) x (energy)

Roentgens per min (R/min)

45
Q

differentiate: Brems vs characteristic XR –> % of XR beam

A

80% Brems

46
Q

differentiate: Brems vs characteristic XR –> XR production –> MOA?

A

Brems: free electron –> pass by atom –> atomic pull of nucleus diverts electron’s path –> slow down –> release XR

charact XR: free electron –> run into inner shell electron –> ejected –> higher shell electron –> mv down to lower shell –> release XR

47
Q

differentiate: Brems vs characteristic XR –> XR energy depend on what?

A

Brems: tube voltage

charact XR: target subst/atom

48
Q

XR production –> what is quality?

A

energy of xray beam –> ability to penetrate object

49
Q

XR production –> what is qty?

A

total #xrays

50
Q

XR production –> increase Z (atomic#) –> what happens to Brems?

A

inc Z –> inc qty (# of Brems xrays)

51
Q

XR production –> increase Z (atomic#) –> what happens to characteristic xray?

A

inc Z –> different quality (energy of charact xray); same qty (#xrays)

52
Q

XR production –> inc kVp –> what happens to:

  • max keV
  • quality
  • qty
  • charact xray
  • intensity
A
  • max keV –> inc to match kVp
  • quality (avg xray energy) –> inc
  • qty –> inc (more Brems)
  • charact xray –> no change
  • intensity –> inc (kVp^2)
53
Q

relationship bw kVp & mA?

A

15% rule:

  • 15% inc kVp –> 1/2 dec mA –> same xray density on film
  • 15% dec kVp –> 2x inc mA –> same xray density
54
Q

xray production –> voltage generator –> inc from single to triple phase (inc voltage ripple –> improve effeciency) –> what happen to:

  • quality
  • qty
A
  • quality: inc

- qty: inc

55
Q

xray production –> inc filtration –> what happen to:

  • quality
  • qty
A
  • quality: inc

- qty: dec

56
Q

what is 10th value layer (TVL; 10th half value layer)? what is it used to calculate?

A

thickness of filtration material to attenuate 90% xrays

used to calc shielding

57
Q

monoenergetic beam –> higher or lower half value layer than a poly-energetic beam, at same kVp?

A

higher

58
Q

fixed 100 kVp –> what is avg Brems energy?

A

avg Brems energy = 1/3 selected kVp

33 keV

59
Q

xray production –> rectified current (more uniform current) –> what happens to:

  • quality
  • qty
  • max energy
A
  • quality: inc
  • qty: inc
  • max energy: no change
60
Q

what happens to focal spot when…

  • inc mA
  • inc kVp
A
  • inc mA –> “blooming” –> wider focal spot

- inc kVp –> “thinning” –> smaller focal spot

61
Q

DEXA –> uses 2 diff photon energies –> 2 methods to do this?

A
  • use filter –> filters out middle –> separate into low & high energy
  • tube voltage –> switch bw low & high
62
Q

DEXA –> radiation dose compared to regular spine xray?

A

VERY low (0.001 mSv vs 1.5)

63
Q

auger electron –> MOA of production?

A

free electron –> strike & eject inner shell electron –> outer shell electron mv down to inner shell –> energy released –> energy transferred to outer shell electron –> gets ejected –> auger electron

64
Q

what is 2ary ionization?

A

auger electron –> ionization

65
Q

what is off-focal radiation? how does it affect…?

  • pt radiation dose
  • image quality
A

anode –> scatter outside focal area

  • inc pt radiation
  • blurry image
66
Q

how prevent off-focal radiation?

A

metal envelope –> attract scattered electrons

67
Q

XR production –> what is leakage?

A

xrays transmitted thru housing

68
Q

XR production –> what is secondary xrays?

A

charact xrays produced from materials other than target (glass, housing, etc)

69
Q

XR production –> what is scatter?

A

xrays that are deflected in direction once leave tube

70
Q

XR production –> what is stray?

A

leakage + scatter

71
Q

beam restriction –> aka?

A

collimation

CORE (33 decks)

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