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Procedures: 3. Treatment Dose and Prescription (EQUATIONS) > Geometric Parameters and Patient Measurements/Treatment Planning Parameters > Flashcards

Geometric Parameters and Patient Measurements/Treatment Planning Parameters Flashcards

Treatment Planning Parameters

1
Q

measurements of the treatment field are defined at _______________

A

isocenter
(width x length)

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2
Q

how is a field size created?

hint - probably more in depth than you’re thinking

A

created by two pairs of the secondary asymmetric collimator jaws

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3
Q

from a base field size, fields can be further shaped via _________

A

MLCs/and or custom Cerrobend blocks

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4
Q

_____ are a document of the field parameters

A

DRRs

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5
Q

the physical radiation field size is delineated at the _____% isodose line

A

50%

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6
Q

what happens to the physical radiation field size at the 50% isodose line?

A

it is delineated

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7
Q

tumor depth is established with ____ imaging

A

3D imaging

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8
Q

tumor depth/depth of a tumor determines ________ and ______ according to Laura Nappi

A

-the energy of the beam
-the type of treatment

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9
Q

superficial tumors are most likely to be treated with __________

A

electrons

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10
Q

deeper tumors are most likely to be treated with __________

A

photons

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11
Q

“Patient Separation” can also be called what? (looking for 3 other names)

A
  • patient thickness
  • intrafield distance
  • innerfield distance (IFD)
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12
Q

what does IFD stand for?

A

Innerfield Distance

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13
Q

what does DRR stand for?

A

Digitally Reconstructed Radiograph

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14
Q

patient separation is measured how and where?

A
  • measured at central axis and at specific points within the treatment field

*think about in class with megan and graph paper and wire

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15
Q

patient separation can be measured using what type of tool?

A

caliper

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16
Q

what is a caliper?

A

a ruler with one sliding leg and one stationary leg

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17
Q

what does SSD stand for?

A

Source to Skin/Surface Distance

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18
Q

what does SAD stand for?

A

Source to Axis Distance

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19
Q

the following is describing SAD or SSD?

  • 100 cm OR it is possible to have it at another specified “fixed”
  • used for electron fields or to be able to obtain larger field sizes
  • used for electron fields
  • distance from the source of radiation to the patient’s skin surface
    -typically what is taken every 5th trt day
A

SSD

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20
Q

the following is describing SAD or SSD?

  • in current LINACS it is located at 100 cm, in older Cobalt-60 machines it is at 80 cm
  • Isocentric technique
  • distance from source of radiation to isocenter (within patient)
  • should never change
A

SAD

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21
Q

T/F:

isocenter can be within or on a patient

A

TRUE

tumor within or superficial tumor!

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22
Q

define “isocentric technique”

A

when the isocenter is located WITHIN the PATIENT

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23
Q

for an isocentric technique SSD is what?

A

less than 100 cm

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24
Q

does a patient need to be moved between fields of an isocentric technique?

A

No

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25
Q

are there more or less chances of error with an isocentric trt?

A

less

26
Q

T/F:

if using an isocentric or SAD technique, the SSD WILL change at different gantry angles

hint - think about clinic and when you check different SSDs like a true lat or AP

A

TRUE

27
Q

there is more chance of error using an SSD or SAD trt

A

SAD is a more sure way, with less chance of error

28
Q

what can an isocentric technique also be called? -

A

SAD technique

29
Q

T/F:

for an SSD technique trt, a patient may need to be moved between fields

A

TRUE

-which causes more chance of error

30
Q

the _________ collimating jaws are movable and asymmetric

A

secondary

31
Q

secondary collimating jaws can create __________ field sizes ranging from __x__ cm to ___x___ cm at the isocenter

A

-rectangular
0x0 cm to 40x40 cm

32
Q

jaws are made of what material?

A

tungsten

33
Q

only ____ percent of transmission through jaws is permitted

A

only <0.5%

34
Q

as field size increases, does collimator scatter decrease OR increase

A

INCREASE

35
Q

T/F:

collimator scatter contributes to dose a patient receives

A

TRUE

36
Q

collimator scatter contributes to dose, therefore, less ____ is needed

A

MU (monitor units)

37
Q

abutting or adjacent fields meet at a determined depth within the patient because of ____________

A

beam divergence

38
Q

to avoid hot spots or cold spots, there must be a _____ on the skin surface

A

gap

39
Q

to avoid hot spots or cold spots, there must be a gap, where?

A

on the skin surface

40
Q

what calculation is commonly used in CSI (craniospinal irradiation)

A

gap calculation

41
Q

what is a common orthogonal field area of possible overlap for CSI (craniospinal irradiation)?

A

laterals for the cranium and PA fields for the spine

42
Q

*Scenario: CSI (craniospinal irradiation)

___________ causes overlap between the cranium and spine fields, and between the multiple spine fields

A

beam divergence

43
Q

what are other techniques to avoid overlap besides the gap calculation? (3)

A
  • half-beam block
  • beam splitters
  • couch rotation (kick)
44
Q

__________ is a technique used to move or change the location of the gap throughout the treatment

A

feathering

45
Q

T/F:

feathering position is adjusted at least 2-3 times throughout the treatment, usually every 5 fractions

A

TRUE

46
Q

_______ blurs any inhomogeneous (not the same) doses within the gap area

A

feathering

47
Q

with Feathering, the ________ axis remains the same, but the field ______ change

A

the central axis remains the same

but the field lengths change

48
Q

image ______ uses multiple imaging modalities to provide better visualization of the patient’s anatomy -
–> the images from the multiple sources are laid over one another to create a more informative image

A

image fusion

49
Q

the following is an example of image fusion - what two images are fused?

A

MRI and CT

50
Q

the following is an example of image fusion - what two images are fused?

A

PET and CT

51
Q

what is another name for the treatment planning computer?

A

Virtual Simulator

52
Q

in the _______ simulator, the physician identifies treatment borders and isocenter

A

virtual

53
Q

what scans are useful for soft tissue?

A

MRI

-commonly used for prostate

54
Q

what scans are useful for showing tumor activity?

A

PET

-commonly fused for lung and HN

55
Q

T/F:

multiple different scans can be fused together to provide for better visualization of the patient’s anatomy

A

TRUE

56
Q

abutting fields meet at a determined depth within the patient because of what?

A

beam divergence

57
Q

for abutting fields, gap is calculated to avoid what? (2)

A

hot and cold spots

58
Q

abutting fields and gap calcs are commonly used for what treatment?

A

CSI - Craniospinal

59
Q

_______ ________ causes overlap between the cranium and spine fields and - between the multiple spine fields

A

beam divergence

60
Q

techniques such as - half-beam block, beam spoilers, or couch kicks/rotations are used to avoid what?

A

overlap and hot spots

Procedures: 3. Treatment Dose and Prescription (EQUATIONS) (3 decks)

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