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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
what is heel effect?
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)
26
XR production device --> angled anode --> heel effect --> side closer to the cathode --> xray beam is stronger or weaker?
cathode side --> more intense beam
27
XR production device --> angled anode --> lrger focus to film distance (FFD) --> what happens to heel effect?
inc FFD --> less variation in xray beam that hits the film --> dec heel effect
28
XR production device --> angled anode --> smaller film (field of view) --> what happens to heel effect?
smaller film --> less variation in xray beam that hits the film --> dec heel effect
29
XR --> thoracic spine --> proper cathode position?
abd aspect
30
XR --> femur --> proper cathode position?
proximal aspect
31
XR --> tib/fib --> proper cathode position?
prox aspect
32
XR --> humerus --> proper cathode position?
prox aspect
33
XR --> forearm --> proper cathode position?
prox aspect
34
pediatric --> XR --> femur --> proper cathode position? why?
distal aspect reduce xray exposure to gonads
35
XR production device --> filter --> purpose?
block low energy xray (soft xray)
36
xray tube --> operates over 70kVp --> what is minimum filtration required?
2.5mm
37
differentiate: keV vs kVp? relationship?
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
higher atomic number --> more or less Bremsstrahlung?
larger atom --> more Brems
39
90-yttrium --> B-emitter --> what should use as shield --> plastic vs lead? why?
plastic --> lower atomic number --> less Brems production
40
tungsten --> K-shell --> binding energy?
-69.5 keV
41
xray tube --> set to 80-150 kVp --> what % of the xrays produced will be K-shell characteristic XR?
10-25%
42
xray tube --> set very high kVp (>300) --> what % of the xrays produced will be K-shell characteristic XR?
negligible %
43
xray tube --> set to 69.0 kVp --> what % of the xrays produced will be K-shell characteristic XR?
0%
44
what is beam intensity? unit?
(#xrays) x (energy) Roentgens per min (R/min)
45
differentiate: Brems vs characteristic XR --> % of XR beam
80% Brems
46
differentiate: Brems vs characteristic XR --> XR production --> MOA?
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
differentiate: Brems vs characteristic XR --> XR energy depend on what?
Brems: tube voltage charact XR: target subst/atom
48
XR production --> what is quality?
energy of xray beam --> ability to penetrate object
49
XR production --> what is qty?
total #xrays
50
XR production --> increase Z (atomic#) --> what happens to Brems?
inc Z --> inc qty (# of Brems xrays)
51
XR production --> increase Z (atomic#) --> what happens to characteristic xray?
inc Z --> different quality (energy of charact xray); same qty (#xrays)
52
XR production --> inc kVp --> what happens to: - max keV - quality - qty - charact xray - intensity
- max keV --> inc to match kVp - quality (avg xray energy) --> inc - qty --> inc (more Brems) - charact xray --> no change - intensity --> inc (kVp^2)
53
relationship bw kVp & mA?
15% rule: - 15% inc kVp --> 1/2 dec mA --> same xray density on film - 15% dec kVp --> 2x inc mA --> same xray density
54
xray production --> voltage generator --> inc from single to triple phase (inc voltage ripple --> improve effeciency) --> what happen to: - quality - qty
- quality: inc | - qty: inc
55
xray production --> inc filtration --> what happen to: - quality - qty
- quality: inc | - qty: dec
56
what is 10th value layer (TVL; 10th half value layer)? what is it used to calculate?
thickness of filtration material to attenuate 90% xrays used to calc shielding
57
monoenergetic beam --> higher or lower half value layer than a poly-energetic beam, at same kVp?
higher
58
fixed 100 kVp --> what is avg Brems energy?
avg Brems energy = 1/3 selected kVp 33 keV
59
xray production --> rectified current (more uniform current) --> what happens to: - quality - qty - max energy
- quality: inc - qty: inc - max energy: no change
60
what happens to focal spot when... - inc mA - inc kVp
- inc mA --> "blooming" --> wider focal spot | - inc kVp --> "thinning" --> smaller focal spot
61
DEXA --> uses 2 diff photon energies --> 2 methods to do this?
- use filter --> filters out middle --> separate into low & high energy - tube voltage --> switch bw low & high
62
DEXA --> radiation dose compared to regular spine xray?
VERY low (0.001 mSv vs 1.5)
63
auger electron --> MOA of production?
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
what is 2ary ionization?
auger electron --> ionization
65
what is off-focal radiation? how does it affect...? - pt radiation dose - image quality
anode --> scatter outside focal area - inc pt radiation - blurry image
66
how prevent off-focal radiation?
metal envelope --> attract scattered electrons
67
XR production --> what is leakage?
xrays transmitted thru housing
68
XR production --> what is secondary xrays?
charact xrays produced from materials other than target (glass, housing, etc)
69
XR production --> what is scatter?
xrays that are deflected in direction once leave tube
70
XR production --> what is stray?
leakage + scatter
71
beam restriction --> aka?
collimation

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