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Laura Nappi online course > Treatment Accessories > Flashcards

Treatment Accessories Flashcards

1
Q

T/F: treatment accessories can further shape and effect the beam and dose distribution

A

true

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2
Q

compensators and compensating filters are designed to create ________ dose and distribution within patient

A

homogenous

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3
Q

where are compensators and compensating filters placed?

A

in between radiation source and patient

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4
Q

compensators and compensator filters must be placed ____ cm from patient during photon therapy

A

20 cm

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5
Q

where are compensators placed for electron therapy?

A

can be placed directly on patient

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6
Q

compensating filters have mostly been replaced by what?

A

IMRT

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7
Q

what is used to reduce scatter to skin surface and maintain skin sparing?

A

compensators and compensating filters

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8
Q

what are compensators and compensating filters made of?

A

high density materials such as Cerrobend or poly-lead

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9
Q

T/F: compensators or compensating filters can be custom made

A

true

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10
Q

what are compensators/compensating filters used/made for?

A

made to absorb dose in areas where there is missing tissue or have irregular surfaces or are curved

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11
Q

of BLT w/ C what are the percentages?
B = ___%

A

50%

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12
Q

of BLT w/ C what are the percentages?
L = ____%

A

26.7%

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13
Q

of BLT w/ C what are the percentages?
T = _____%

A

13.3%

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14
Q

of BLT w/ C what are the percentages?
C = _____ %

A

10%

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15
Q

Blocks are positioned on a tray meaning a ____ factor would be needed when calculating MU

A

tray

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16
Q

the following is describing Hand blocks, Cast blocks, Positive blocks, or Negative Block –>
*individualized for each patient
*cut to match beam divergence, reducing penumbra

A

cast block

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17
Q

the following is describing Hand blocks, Cast blocks, Positive blocks, or Negative Block –>
*blocks the center field and leaves periphery open

A

Positive block
*fist bump = the block in middle = POSITIVE

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18
Q

the following is describing Hand blocks, Cast blocks, Positive blocks, or Negative Block –>
*blocks the periphery and leaves the middle/center open

A

Negative block

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19
Q

the following is describing Hand blocks, Cast blocks, Positive blocks, or Negative Block –>
*pre-made and not custom
*non divergent (sides do not match angle of the beam, creating penumbra)
*high density materials

A

Hand blocks

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20
Q

what is the common thickness of Lead blocks?

A

6 cm

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21
Q

blocks are typically made of what materials?

A

Cerrobend or lipo-witz metal

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22
Q

what makes up a Cerrobend block?

A

Bismuth, Lead, Tin, Cadmium

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23
Q

what degree (C) melts Cerrobend?

A

74 degrees C

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24
Q

transmission of a radiation beam through a block is ___%

A

< 5 %

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25
Q

what is the block transmission factor? and what does it mean?

A

< 5%, meaning block needs to be around 4-5 HVLs thick

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26
Q

how do you find Cerrobend equivalent of a lead block?

A

multiple the lead thickness by 1.21 !!!

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27
Q

____ cones and cutouts are used to confine and collimate beam close to patient’s skin surface

A

electron

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28
Q

T/F: electron cones come in multiple sizes

A

true

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29
Q

T/F: e- cutouts can be customized

A

true

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30
Q

e- cutouts reduce beam transmission by how much? __%

A

< 5%

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31
Q

electron cutouts reduce beam dose rate so we must use a ____ factor when calculating MU for e- plans

A

cutout

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32
Q

what is formula for –> thickness of lead needed to stop electrons?

A

(1/2 of the energy in MeV) + 1
*answer should be in mm, cause e- don’t need thicker blocks like photons do

33
Q

what treatment accessory shields critical structures behind treated areas

A

internal shields

34
Q

internal shields are mainly seen during photon or e- therapies?

A

electron

35
Q

a Z # is the same as ______ #

A

atomic

36
Q

an internal shield is a lead covered material with a ___high/low___ atomic # (Z)

A

low

37
Q

aluminum, wax, and plastic are example of what treatment accessories… -cutouts, -bolus, -wedges, or -internal shields

A

-internal shields

38
Q

what areas usually call for internal shields? and what do the shields protect?

A

eyelids - protects optic lens, lacrimal glands; nostrils - protects nasal membranes; earlobes; lips - protects gingiva, tongue

39
Q

if only lead were used for internal shields and we would not cover it low atomic # material… what would happen?

A

if only lead were used, uncovered, there would be too much backscatter, adding to the dose

40
Q

bolus is placed ___directly/indirectly___ on skin surface

A

directly

41
Q

_____ eliminates the skin-sparing effect in photon therapy

A

bolus

42
Q

bolus compensates for what?

A

irregular surface contours

43
Q

_____ eliminates air gaps in treatment field

A

bolus

44
Q

what is bolus made of?

A

tissue equivalent material

45
Q

T/F: bolus can be multiple thicknesses

A

true

46
Q

wax, polystyrene, Lucite, and superflab are all possible materials of ________

A

bolus

47
Q

bolus __lowers/raises___ dmax so dose is ___more/less___ superficial

A

bolus raises dmax so dose is more superficial

48
Q

T/F: bolus is part of prescription and much be prescribed by rad onc in order to be used on patient

A

true

49
Q

a beam spoiler is used mainly for what treatment?

A

TBI

50
Q

a beam spoiler reduces skin ______ and increases surface dose

A

sparing
*like a giant bolus

51
Q

a beam spoiler is made of __-__ cm of ____

A

1-2 cm of acrylic

52
Q

a beam spoiler brings surface dose to __% of prescribed dose, which is what we need/want for TBI treatments

A

90%

53
Q

where are beam spoilers placed in relation to patient

A

as close to patient as possible

54
Q

wedges __increase/decrease__ beam’s intensity across the beam

A

decrease

55
Q

______ tilt isodose curves

A

wedges

56
Q

physical wedges are made of __low/high___ density material

A

high

57
Q

______ wedges are placed in treatment head

A

physical wedges

58
Q

universal/dynamic wedges use ____ to mimic same effect as physical wedges

A

jaws

59
Q

on Varian machines, what jaw is used by dynamic wedges to mimic a wedge?

A

the Y jaw

60
Q

___ of wedge absorbs beam, and the ____ transmits it

A

heel absorbs and the toe transmits it

61
Q

_____higher/lower____ wedge angle, ie. heel is… steeper the isodose distribution will be

A

higher

62
Q

the ___ of wedge brings the isodose curve up closer to the skin surface!

A

heel
-makes sense since beam there is attenuated more and there is less penetration, like there is closer you get to toe

63
Q

example question for wedge heel positioning -
“if heel of wedge is positioned anteriorly on a RT lat, what is position on LT lat?”

A

LT lat would also have an anteriorly positioned heel

64
Q

for HIGH or LOW energy beams, the wedge angle is found at the 50% isodose curve or 80%

A

low energy

65
Q

for HIGH or LOW energy beams, the wedge angle is found at 10 cm depth

A

high energy

66
Q

wedges can also absorb some of the primary beam, which would require a __lower/higher__ MU to compensate for loss of dose

A

higher

67
Q

MLC stands for what?

A

multileaf collimators

68
Q

how many MLC leaves are there typically

A

52-160 leaves

69
Q

what are MLCs made of?

A

Tungsten

70
Q

T/F: each MLC leaf has the ability to move independently to create a wide variety of treatment shapes

A

true

71
Q

MLCs are controlled by what?

A

computer

72
Q

____ reduce need for cast blocks and compensators

A

MLCs

73
Q

what is the permissible percent through MLCs?

A

< 2%

74
Q

IMRT plans use which MLC technique more commonly - step n shoot (MLCs do not move while beam is on) OR dynamic (MLCs move while beam is on)

A

dynamic

75
Q

describe Step n Shoot and Dynamic MLCs -

A

Step n Shoot MLCs do not move while beam is on; once beam is off they move/re-shape; commonly used for 3D plans
Dynamic MLC move while beam is on; commonly used for IMRT

76
Q

3D plans use Dynamic MLC or, Step n Shoot MLCs?

A

Step n Shoot

77
Q

YES or NO - the following wedges in the picture are positioned correctly

A

YES

78
Q

which of the two blocks is a POSTIVE BLOCK and which is a NEGATIVE BLOCK?

A

A = POSITIVE
B = NEGATIVE

Laura Nappi online course (54 decks)

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