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Dosimetry > Linac Components > Flashcards

Linac Components Flashcards

1
Q

3 main components of linac

A

drive stand, gantry, tx couch

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2
Q

modulator sends

A

sends high voltage flat topped pulsating DC current to klystron & magnetron & e- gun

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3
Q

fan control switch is part of

A

modulator cabinet

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4
Q

fxn of fan control switch

A

auto turn on/off as needed for cooling

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5
Q

aux power distrib panel contains what button

A

emergency off button

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6
Q

prim power distrib panel supplies

A

major power route

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7
Q

magnetron is the source of

A

high freq microwaves in lower E

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8
Q

klystron is a ? amplifier

A

microwave amplifier (not a source) used for high E

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9
Q

klystron is a component of

A

drive stand

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10
Q

wave guide is made of

A

copper pipes filled w/freon, hexaflouride, or HF6/sulfur

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11
Q

grid pulse is the force that drives

A

e- to the accelerator tube

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12
Q

circulator prevents ?

A

backflow of microwaves

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13
Q

e- gun is a component of

A

gantry

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14
Q

e- gun introduces

A

e- into accelerator tube

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15
Q

accelerator guide is mounted in what direction

A

mounted horizontally & vertically

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16
Q

traveling wave accel tube allows e- to ride on ?

A

high freq microwave in 1 direction only

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17
Q

in standing wave accel tube, alternating EM flds produce ?

A

2 alternating high freq waves moving in opposite directions

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18
Q

drift tube are bunching cavities that regulate?

A

speed of e- so they arrive in bunches

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19
Q

bending magnet is a component of

A

tx head

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20
Q

bending magnet changes directions of e- and directs them

A

vertically toward pt

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21
Q

target is what kind ?

A

transmission target

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22
Q

primary collimator limits what

A

max fld size

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23
Q

beam flattening filter used for what beam

A

photon beams only

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24
Q

scattering foil used for what beam

A

e- beams only

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25
Q

monitor ion chamber located where

A

before 2nd collimator

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26
Q

secondary collimators aka

A

jaws

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27
Q

MLC define what

A

define field size & shape

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28
Q

linac temp

A
  • 40 deg C or 104 deg F

- beyond sys will shut down

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29
Q

photon flow thru head

A

bending mag->target->prim coll->flattening filter->ion chamber->sec coll->wedge->block

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30
Q

e- flow thru head

A

bending mag->prim coll->scattering foil->ion chamber->sec coll->e- cone

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31
Q

dynamic wedge has minimum ? in wedge direction

A

field size

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32
Q

concrete vs lead price

A

concrete less expensive

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33
Q

compensating filter retains what

A

skin sparing advantage is retained

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34
Q

wedge filter reduces dose over

A

sloping & obl surface

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35
Q

compensating wedge compensates for

A
  • partial field or irregular shape contour

- missing wedge of tissue

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36
Q

beam hold occurs when dose rate is

A

too high for mlc to reach proper position

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37
Q

thoraceus filter made up of what

A

tin-copper-aluminum (cat)

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38
Q

dose monitor unit of linac located

A

w/i tx head

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39
Q

e- E selected on linac indicates ? on skin surface

A

probable E

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40
Q

e- beam collimated as close to

A

the source

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41
Q

sagital laser aligns with

A

axis of gantry rotation

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42
Q

mlc main advantage

A

generate field of nearly any size & shape

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43
Q

auxiliary power distribution panel is located where

A

modulator cabinet

44
Q

primary power distribution panel is located where

A

modulator cabinet

45
Q

pump breaker is located where

A

modulator cabinet

46
Q

aux power distrib panel shuts off

A

power to unit

47
Q

aux power distrib panel fuses

A

power & timer for filament

48
Q

high volt power supply breaker protects modulator by

A

tripping off when overload

49
Q

microwaves flow thru ? to accelerator tube

A

waveguide

50
Q

gas in ? helps keep microwave from breaking down

A

waveguide

51
Q

wave guide is a component of

A

drive stand

52
Q

grid pulse is a component of

A

drive stand

53
Q

circulator is a component of

A

drive stand

54
Q

mach output controlled by variance in ? & RF

A

grid pulse

55
Q

? connects klystron to accelerating tube

A

circulator

56
Q

accelerator guide is a component of

A

gantry

57
Q

drift tube is a component of

A

gantry

58
Q

failure of ? affects output E

A

e- gun

59
Q

? similar to cathode

A

e- gun

60
Q

e- gun made of what metal

A

W (tungsten)= high Z, high temp

61
Q

magnetic field interacts with EM microwaves in what

A

accelerator tube

62
Q

microwaves have a very distinct

A

path

63
Q

e- need to follow ? path in accelerator guide

A

microwaves

64
Q

traveling wave accel tube must be

A

gas evacuated

65
Q

how many bunching cavities in high E linac

A

5

66
Q

primary collimator is a component of

A

tx head

67
Q

target is a component of

A

tx head

68
Q

beam flattening filter is a component of

A

tx head

69
Q

scattering foil is a component of

A

tx head

70
Q

monitor ion chamber is a component of

A

tx head

71
Q

secondary collimator is component of

A

tx head

72
Q

MLC is a component of

A

tx head

73
Q

ODI is a component of

A

tx head

74
Q

bending magnet for high E is

A

270 deg

75
Q

bending magnet for low E is

A

90 deg

76
Q

bending magnet for very low E is

A

no magnet b/c mounted vertically

77
Q

focal spot of e- stream upon exiting magnet is ?

A

3mm

78
Q

target is made of what

A

W- tungsten

79
Q

target is retracted for ?

A

e-

80
Q

primary collimator is fixed or able to move

A

fixed

81
Q

primary collimator is located where in tx head

A

below target and above flattening filter/scattering foil

82
Q

beam flattening filter makes the beam more?

A

homogenous

83
Q

beam flattening filter shape

A

thicker in center and thinner at edges

84
Q

beam flattening filter located where

A

on carousel in tx head

85
Q

beam flattening filter does what

A

absorbs more photons from center & less from periphery of beam

86
Q

scattering foil is made up of what

A

2 foils stacked on each other, separated by a few cm

87
Q

scattering foil closest to source is made of what/does what?

A
  • Pb

- scatters (broadens) beam & makes 3mm pencil beam

88
Q

scattering foil lower made of what/does what?

A
  • low Z

- flattens e- beam

89
Q

scattering foil located where

A

carousel in tx head

90
Q

scattering foil can create what radiation

A

usu < 5% brems

91
Q

monitor ion chamber registers what

A

radiation output (integrated dose) & records field flatness & beam symmetry

92
Q

monitor ion chamber how many

A

2 required

93
Q

secondary collimators do what

A

moveable & define field size

94
Q

dynamic wedge has minimum ? at toe of wedge

A

collimator setting

95
Q

dynamic wedge has minimum what?

A

MU

96
Q

dynamic wedge not compatible with what on some blocked fields

A

MLC direction

97
Q

concrete vs lead shielding of n

A
  • concrete better

- Pb must have borated plyethylene to shield n

98
Q

concrete vs lead installation

A

concrete easier

99
Q

compensating filter used to avoid

A

bolus effect

100
Q

compensating filter distance from pt

A

at least 15 cm (20cm according to khan)

101
Q

compensating filter shaped to mimic

A

various depths of missing tissue

102
Q

compensating filter made of what

A

Al, Pb, Pb plastic, cerrobend

103
Q

compensating filter used most with what tx

A

lung, h&n

104
Q

wedge filter depends on

A

depth & field size

105
Q

wedge filter is the angle between

A

50% isoline & perpendicular to beam CAX

106
Q

wedge filter higher E machines use

A

70-80% isolines with wedge

107
Q

beam hold is when the beam is turned off until

A

mlcs catch up

Dosimetry (53 decks)

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