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Radiation Therapy > Treatment & Planing (Exam 1) > Flashcards

Treatment & Planing (Exam 1) Flashcards

1
Q

2 parts of simuaiton

A

Localization & Verification

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2
Q

Geometric definition of the position and extent of the tumor or anatomical structures by reference of surface marks that can be used for treatment setup and skin care instructions.

A

Localization

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3
Q

Final check that each of the planned treatment beams overs the tumor or target volume before actual first treatment and match up

A

Verification

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4
Q

Material with high atomic number, lead, copper, solder wire used on a surface or in a body cavity of a patient to delineate special points of interest or critical structures.

*This will show up on xray

A

Radiopaque Marker

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5
Q

Measurement of the thickness of a patient among the central axis.

A

Separation or Intrafield Distance (IFD)

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6
Q

Distance to Isocenter is always 100cm

A

SSD

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7
Q

Dimensions of the treatment field at isocenter, represented by width x length or length x width

A

Field Size

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8
Q

Indicates the gross palpable or visible tumor

A

Gross Tumor Volume (GTV)

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9
Q

Indicates the gross palpable or visible tumor and surrounding volume of tissue that may contain subclinical or microscopic disease.

A

Clinical Target Volume (CTV)

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10
Q

Indicates the CTV plus margins for geometric uncertainties, such as patient motion, beam penumbra, and treatment setup differences.

A

Planning Target Volume (PTV)

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11
Q

tumor & any other tissue with presumed tumor.

A

Target Volume (TV)

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12
Q

encompasses additional margins around the target voume for limitations in treatment technique.

A

Treatment Volume

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13
Q

volume of tissue receiving a significant dose >50% of specified target dose. Tissue in front of, behind, and around the target volume.

A

Irradiated volume

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14
Q

An advantage of a source-axis distance treatment compares to a s source-distance treatment (Assuming a patient is NOT required to move in either set up.)

A

Table adjustments between fields are not normally required

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15
Q

The backscatter factor is effected by

A

Quantity of radiation

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16
Q

The tissue air ratio (TAR) at the depth of a maximum electron buildup (Dmax) is.

A
  1. Always les than or equal to 1
  2. The backscatter factor
  3. Dependent on the field size
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17
Q

The concept of tissue-air ratio (TAR) is most commonly employed for calculations involving.

A

SSD varying fields

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18
Q

The depth of maximum ionization is most dependent on

A

Beam energy

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19
Q

A 10 MV linear accelerator is used at 100cm SSD. The location of maximum dose is found at a depth of:

A

2.5cm

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20
Q

Percentage depth dose increases with increasing

A

Energy and field size

Directly proportional with everything except Depth

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21
Q

Tissue-air ratio decreases with decreasing

A

Field Size

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22
Q

A wedge filter ________ the output of the beam and must thus be taken into account in the treatment calculations.

A

decreases

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23
Q

%DD increases with increasing.

A

Energy and field size

Directly proportional with everything except Depth

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24
Q

TAR decreases with decreasing

A

Field Size

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25
Q

When blocking is used in a treatment calculation, the area of the collimator is used in determining

A

Output factor

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26
Q

Which of the following is not a tissue absorption factor

A

Output factor

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27
Q

What central axis depth dose quantities would most likely be used to computer an accurate MU setting on an 18-MV unit for an isocentric treatment?

A

TMR

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28
Q

Two parallel opposed equally weighted 6-MV fields are separated by 20cm of tissue and treated with an SSD technique. The maximum dose will occur

A

1.5cm under the skin surface

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29
Q

A wedge filter _____ the output of the treatment beam and must thus be taken into account in the treatment calculation.

A

decreases

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30
Q

Mayneord’s factor is used to convert

A

PDD with a change in SSD from the standard

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31
Q

1 Gy is the same as:

A

100 cGy

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32
Q

The point of maximum electron equilibrium is referred to as

A

Dmax

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33
Q

Dose rates

A

increase with increased field size and decrease with increased distance

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34
Q

In a fixed SSD technique, the dose is routinely normalized

A

at Dmax

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35
Q

In an isocentric treatment technique, the dose is routinely normalized

A

at the isocenter

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36
Q

What is the reference desert when delivering an external beam radiation therapy treatment using a 10 MV SSD technique

A

.968

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37
Q

What is the reference desert when delivering an external beam radiation therapy treatment using a 18 MV SSD technique.

A

.944

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38
Q

Calculate the equivalent square of a 13x12cm field blocked 12%

A

11.7

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39
Q

Calculate the equivalent square of a 13x9cm field blocked 7%

A

10.3

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40
Q

The gross tumor volume (GTV), as defined by the ICRU, means:

A

The gross/palpable or visible/demostrable tumor extent to be irradiated to a specified dose

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41
Q

The term clinical target volume (CTV), as defined by the ICRU, means

A

a tissue volume that contains a demonstrable GTV and/or subclinical microscopic malignant disease, which has to be eliminated

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42
Q

The field size when using an SSD technique and a photon beam is usually define

A

on the skin surface

43
Q

The angle of beam divergence is

A

larger farther from the CAX

44
Q

The three planes in a patient are across the body, along the body in a lateral view, and along the body in than anterior view. Respectively they are referred to as

A

axial, sagittal and coronal

45
Q

When the treatment field is designed by the radiation oncologist, margins are always added around a tumor because of:

A

uncertainties in determining tumor extent, penumbra of the beam, and patient motion

46
Q

The isoventer is

A

the point around which the source of the beam rotates

47
Q

what is the reference desert when delivering an external beam radiation therapy treatment using 6MV SSD technique

A

.993

48
Q

What is the reference desert when delivering an external beam radiation therapy treatment using a 6MV SAD technique

A

1.04

49
Q

What is the percent depth dose of a 12x7cm field delivering a 10MV -ray at a depth of 2.5cm

A

100.0

50
Q

What is the percent depth dose of a 12x7cm field delivering a 18MV x-ray at a depth of 2.5cm

A

97.3

51
Q

What is the TAR of a 10x16cm field blocked 5% delivering a 10 MV x-ray at a depth of 10.0cm

A

.866

52
Q

The depth of maximum ionization is most dependent upon:

A

beam quality

53
Q

TAR is dependent upon:

A

energy
depth
field size

54
Q

When using shielding blocks, which of the following is effected

A

Equivalent square field

55
Q

The intensity of a high energy photon beam at any given distance from a source is

A

inversely proportional to the square of the distance

56
Q

dose rate for a linear accelerator is expressed as

A

cGy/mu

57
Q

TAR is advantageous because

A

ratios do not depend on source to skin distance

58
Q

Mayneord factor compensates for a change in central axis depth dose and includes corrections for

A

inverse square law

59
Q

which beam would produce the maximum amount of backsatter

A

1.25MV

60
Q

As beam quality increases, maximum dose

A

increases

61
Q

the %DD for a 12x12cm field, 4MV photon beam, 5cm depth, and 80cm SSD is 82.8. Calculate the %DD for the same field size and depth for 100cm SSD.

A

84.3

62
Q

If the field size indicator is set for 20x20cm at 80cm SSD, what is the field size at 84cm

A

21x21cm

63
Q

If a Co-60 unit is used at 80cm SSD for 15x15cm field size and has a %DD of 58.4 at 10cm depth what is the %DD for the same field size and depth at 100cm SSD

A

60.9

64
Q

Mayneord’s F-factor is of use when there is a change in

A

SSD

65
Q

Calculate the equivalent square for a 10x15cm rectangular field

A

12x12cm

66
Q

Determine the equivalent square for a rectangular field with a width of 8cm and a length of 15cm

A

10.4cm

67
Q

Determine the equivalent square for a rectangular field with a width of 7cm and length of 17cm

A

9.9cm

68
Q

The counterpart of the timer setting of aCo-60 unit is most similar to the _____ of a linac

A

monitor unit

69
Q

As energy of a photon beam increases, the dose buildup region ______.

A

moves deeper below the sin surface.

70
Q

The angle between the central axes of two beams is called the

A

hinge angle

71
Q

The use of a split beam/half beam technique is advantageous due to

A

preventing beam divergence

72
Q

Two treatment fields on a patient with cancer of the maxillary sinus have a hinge angle of 90 degrees

A

15

73
Q

If one HVL shield is 2.5cm thick how much would the radiation be reduced to with a 5cm thick shield

A

25%

74
Q

Calculate the equivalent square of a 4x11cm field

A

6cm

75
Q

calculate the equivalent square of a 6x20cm field

A

9cm

76
Q

calculate the equivalent square of a 12x17cm field

A

14cm

77
Q

calculate the equivalent square of a 7x8cm field

A

7.5cm

78
Q

What is the given dose for a patient receiving 250cGy a day treated at a 5 cm depth with SSD technique, if the %DD is 84.5%?

A

296

GD= (250/.845) = 295.8= 296cGy

79
Q

Three half-value layers would reduce the intensity of the beam to

A

12.5%

80
Q

The field size light should correspond to the _______ %Isodose line.

A

50

81
Q

Three half-value layers would reduce the intensity of the beam to:

A

12.5%

82
Q

The optimum hinge angle for a pair of 45 degrees wedge filters, neglecting oblique incidence is?

A

90 degrees

83
Q

The wedge filter is used during external beam radiation of glottic tumors to

A

evenly distribute dose

84
Q

An ideal bolus material should have all of the following except

A

valence number

85
Q

Calculate the hinge angle for a 30 degree wedge

A

120

86
Q

An area outside the target area which receives a higher dose than the specified target dose is

A

hot spot

87
Q

____is the measurement of radiation dose

A

dosimetry

88
Q

the ______ is the sameness from side to side of the beam profile

A

symmetry

89
Q

The dose is highest at the ______ of a photon beam

A

central axis

90
Q

A _____ isodose curve willl have an hourglass shape of the highest intensity isodose line

A

parallel opposed field

91
Q

A ____ is the use of independent variable secondary collimator jaws moving during treatment

A

dynamic wedge

92
Q

The reference desert for linear accelerators is

A

1 cGy/MU

93
Q

Stereotactic radiosurgery utilizes

A

non-conplaner beams

94
Q

A ______ method uses more than 4 fields with extensive blocking

A

conformal

95
Q

The process of converting dose distribution to percent of a dose at some point is termed

A

normalization

96
Q

Isodose distributions are _____ -dimensional representations of the spatial distribution of dose:

A

three

97
Q

Wedge-field asides distributions are characterized by increased radiation intensity under the _____ of the wedge:

A

toe

98
Q

IMRT is a treatment planning and delivery process that seeks to achieve treatment plan optimization by varying the _____intensity of the treatment beams in addition to their position

A

intensity

99
Q

The quality of DRRs can be improved by _______the thickness of CT slices

A

decreasing

100
Q

When an immobilization device is needed, it is best

A

first determine the beam orientation and then build the device

101
Q

A lung boost is often delivered via

A

POP AP/PA with a midline block

102
Q

Without adjustment of output factors, dose rates

A

increase with decreased field size and decrease with increased distance

103
Q

A dose of 30000 cGy is to be delivered at a depth of 8cm at a percent depth dose of 76%. What is the dose to an organ at 14cm depth and a percent depth dose of 58%?

A

3000(.58)/(.76)= 2289

Radiation Therapy (3 decks)

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