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Laura Nappi online course > Radiation Fields > Flashcards

Radiation Fields Flashcards

1
Q

T/F: radiation fields can differ depending on location of tumor and depth of tumor

A

TRUE
-every plan and patient can be unique however there are some standards

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2
Q

a single field, can also be called a single ____

A

port

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3
Q

single fields are used to treat what type of treatments?

A

superficial electron fields or palliative trts

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4
Q

why aren’t single fields super common?

A

because the dose distribution is not ideal for MV beams

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5
Q

the following are examples of which radiation field?

-AP IM chain
-PA spine
-supraclavicular nodes

A

single field

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6
Q

the following is an example of what radiation field?
*hint - notice there is no high isodose line on other side of patient

A

single field

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7
Q

T/F: you can use “Field” and “Port” interchangeably

A

TRUE

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8
Q

Parallel Opposed Fields (POPs) have ___ treatment fields/ports aimed at/in opposing directions

A

2

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9
Q

POP stands for -

A

Parallel Opposed Ports

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10
Q

POPs have a hinge angle of _____ !!!

A

180 degrees

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11
Q

POPs have a ______ dose distribution !!!

A

homogenous

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12
Q

POPs are used for more ____curative/palliative____ treatments?

A

curative

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13
Q

for POPs 2 fields are aimed along the same ____ from opposite sides

A

same axis

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14
Q

AP/PA and RT lat/LT lat are examples of what radiation field?

A

Parallel Opposed Fields//Ports

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15
Q

POPs lead to higher ____ doses, therefore it is even more common to use more than two fields to reduce these reactions

A

skin

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16
Q

_____ are the simplest form of multiple fields, and are very reproducible

A

POPs

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17
Q

_____ have a homogenous dose to tumor

A

POPs (Parallel Opposed Ports/Fields)

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18
Q

the following is an example of what radiation field?

A

POPs (Parallel Opposed Ports/Fields)

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19
Q

For which radiation field, is there less sparing of tissues around tumor - when it is compared to the other techniques

A

POPs

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20
Q

good note - in general, multiple fields (so anything over a single field) are used more for ___curative/palliative___ treatments

A

curative

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21
Q

___less/more___ fields allow for higher doses to the tumor and lower doses to surrounding OARs

A

more!!!! with more fields you can conform to tumor better and find more angles to avoid OARs

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22
Q

a “hot spot” would indicate overdose, or underdose?

A

overdose

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23
Q

a “cold spot” would indicate overdose, or underdose?

A

underdose

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24
Q

Concept Check! - For parallel opposed fields, the fields must be parallel… so if they are NOT fully opposing… what would you check/fix?

A

check to see if between the 2 parallel opposed fields the collimator was flipped OR if the jaws were flipped/reversed
–one or the other, not both collimator AND jaws

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25
Q

if both the collimator and jaws were flipped for your POPs, is this good or bad? and Why

A

bad - only one can flip/be reversed… because if BOTH the collimator and jaw were flipped between fields, it will be like nothing changed on the opposite field

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26
Q

if using blocks for POPs what must you do between fields?

A

FLIP THEM
–tbt to sim lab!

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27
Q

the following is a POP field, can we treat if it looks like this?

A

NO - the POPs are not fully opposed

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28
Q

for POPs, the gantry is the exact _____ between the 2 fields, and field size is a ____ image

A

gantry is exact opposite (ie. parallel) and field size is a mirror image

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29
Q

why does the POP fields look like this? is it wrong or right?

A

because neither the collimator or field size were adjusted

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30
Q

in the following POP example - is the collimator or jaws adjusted?

A

collimator

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31
Q

in the following POP example - is the collimator or jaws adjusted?

A

jaws

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32
Q

____ are used when dose distribution is uneven

A

WEDGES

33
Q

wedges are always positioned ____ to ____

A

heel to heel

34
Q

if a wedge is positioned heel to toe, what happens?

A

they just cancel each other out

35
Q

when an odd number of fields are used (like a 3-fld technique), there is ___even/uneven____ dose distribution

A

uneven — a wedge is then applied

36
Q

3-field techniques are commonly used for what type of tumors?

A

tumors within the abdomen that are closer to the surface; anteriorly positioned tumors

37
Q

looking at the example of the 3-fld technique below, where would the tumor be positioned?

A

anteriorly

38
Q

looking at the example of the 3-fld technique below, where would the tumor be positioned?

A

more posterior

39
Q

in the following diagram, the heel of the wedge is placed more anterior or posterior? - and WHY

A

more anterior - it is good that heel is placed anteriorly because there is an AP field part of the 3 flds, so there would be more dose there than anywhere else. Having the heels anteriorly, reduce hot spot/overdose and even out dose

40
Q

what radiation/treatment field(s) is/are used for tumors deep within the abdomen or pelvis?

A

4 field technique

41
Q

4 field technique is also known as what?

A

4 field box

42
Q

each field of a 4 field box/technique are ___ degrees apart

A

90 degrees

43
Q

what radiation field is considered a combination of two parallel opposed fields?

A

a 4-field box/technique

44
Q

the following diagram is of what radiation field?

A

4 field box/technique

45
Q

what radiation field is used for small, superficial tumors that are up to 7 cm within skin surface

A

wedge pair

46
Q

if we treated the parotid gland, what radiation field(s) would we be likely to use?

A

a wedge pair

47
Q

a wedge pair radiation field has a hinge angle of ______

A

LESS THAN 180 degrees

48
Q

T/F: for a wedge pair technique where the beams overlap there is still higher dose

A

true!! for a wedge pair technique, where the beams overlap is where we want max dose to be - the wedges are just employed to help reduce hot spots

49
Q

for a wedge pair technique, there is rapid ______ after the area of overlap

A

dose fall off

50
Q

why is a wedge pair technique optimal for superficial tumors?

A

after the area of overlap, there is rapid dose fall off - thus reducing dose distally for OARs

51
Q

a ____ angle is the angle between 2 fields !!!!!

A

HINGE

52
Q

for a wedge pair radiation field, a hot spot of ___% is acceptable, but nothing higher

A

+10%

53
Q

where is dose highest at for a wedge pair radiation field?

A

dose is highest at the superficial/proximal region of overlap

54
Q

the following diagram is of what radiation field(s)?

A

wedge pair technique

55
Q

for which radiation field is the gantry stationary while the beam is ON?

A

a fixed field

56
Q

for a fixed field(s), the gantry moves when?

A

in between trt fields… does not move while the beam is ON

57
Q

another name for fixed fields is _________

A

step n’ shoot

58
Q

to help identify fixed fields, you can look for what effect?

A

the starfish effect!

59
Q

the starfish effect on fixed fields, represents what?

A

each individual exit dose

59
Q

the choppy green on this diagram of a Fixed Field is representing what effect?

A

the starfish effect

60
Q

which radiation field has the gantry moving, while the beam is on?

A

rotational fields/VMAT arcs

61
Q

which radiation field(s) are BEST for small deep-seated tumors?

A

rotational arcs/fields ; vmat

62
Q

the following is fixed fields or rotational fields?

A

rotational - not as choppy like starfish effect… rotational has smoother lines (also there are arrows rotating around patient contour)

63
Q

of what radiation field(s) does it’s dmax get displaced anteriorly?

A

partial arcs

64
Q

for partial arcs the gantry moves LESS THAN ____

A

360 degrees !!!! makes sense - not a full arc, a partial! so not going full 360 degrees

65
Q

for a full arc the gantry rotates ____

A

a full 360 degrees

66
Q

a full arc dmax is located at the ___

A

center/isocenter

67
Q

a partial arc dmax is located where?

A

more anterior … to help correct for that we use past pointing

68
Q

past pointing is used for partial arcs why?

A

past pointing (PP) has the trt planned past the tumor THAT WAY dmax lands ON the tumor

69
Q

to help trick the machine into placing dmax at isocenter for a partial arc, we use ______

A

PP (past pointing)

70
Q

past pointing corrects ____ arc dmax misplacement

A

partial arc dmax displacement

71
Q

for a partial arc, we plan to trt at a past point, that way what happens?

A

that way dmax ends up where we want/desired depth

72
Q

label in the following partial arc diagram -

  • where dmax is w/o past pointing
    -where the past point is
    -and where the dmax is with use of past pointing
A
  1. -where the past point is
  2. -where the dmax is with use of past pointing
    • where dmax is w/o past pointing (notice how it winds up more anterior in body)
73
Q

what radiation field is being used in the diagram?

A

PARTIAL ARC – we know this due to isodose lines only covering one side of head AND looking at partial arrow ; don’t get it confused with wedge pair… there are not wedges here!!!

74
Q

field weighting can also be called what?

A

beam weighting

75
Q

how can you calculate dose per field? what about MU per field?

A

Dose per field = Total Dose x (weight of field/sum of all field weights)

MU per field = Total MU x (weight of field/sum of all field weights)

76
Q

T/F: different fields//beams can deliver unequal amounts of dose

A

true

77
Q

calculate the dose delivered to the PA field

A

200 cGy
**dose per field = TOTAL DOSE x (weight of field / sum of all field weights)

Laura Nappi online course (54 decks)

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