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Dosimetry > General Brachytherapy > Flashcards

General Brachytherapy Flashcards

1
Q

radium-226 decay process of ? isotope results in stable ? isotope?

A

part of decay process of Uranium-238 resulting in stable Pb-206

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2
Q

Ra/daughter equilibrium takes how long to reach?

A

30 days

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3
Q

uniform sources have same concentration of radioactivity through entire ?

A

length

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4
Q

Cs-137 decays ?% in 6 months

A

1%

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5
Q

Cs-137 used for what implants?

A

gyn

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6
Q

Pd-103 decays by ? to ?

A

by e- capture to Rh-103

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7
Q

P-32 t1/2

A

14.3 days

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8
Q

P-32 used for what implants

A

intravascular & peritoneum

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9
Q

Ir-192 decays ? % per day

A

1%

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10
Q

Au-198 decays by what to what

A

B- to Hg-198

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11
Q

I-125 emits what

A

pure gamma emitter

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12
Q

Sr-90 emits what

A

pure beta emitter

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13
Q

activity aka

A
  • strength of source
  • rate of decay
  • # of nuclei decaying per sec
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14
Q

decay constant incr then activity ?

A

incr; directly prop

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15
Q

decay constant is the total # ? that decay per unit time

A

total # of atoms that decay per unit of time

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16
Q

t1/2 incr then overall activity ?

A

decr; inv prop; decay decr

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17
Q

average E is the avg value of ? from each isotope

A

all emitted photons from each isotope

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18
Q

specific activity is the activity per unit ? of radioactive material

A

mass

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19
Q

specific activity decr then activity per gram ?

A

decr; directly prop

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20
Q

Ci is ? dps

A

3.7 x 10^10 dis/sec

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21
Q

Bq is ? dps

A

1 dis/sec

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22
Q

fletcher suite applicator is made up of ?

A
  • uterine tandem
  • cervical colpostats (ovoids)
  • capsules for uterine
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23
Q

heymans capsules are used when ? still intact

A

uterus

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24
Q

delclos is used for ? afterloading

A

uterine-vag

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25
Q

burnett applicator is use for tx of ?

A

tx vaginal tissues

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26
Q

Ra-226 dose distrib based on

A

calcs

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27
Q

square or rectangular implants aka

A

planar implant

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28
Q

multiple plane implants are spaced how far apart

A

1 cm apart & parallel

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29
Q

with volume implants, more than ? planes of sources are used

A

2

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30
Q

quimby/memorial system is similar to ?

A

paterson

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31
Q

quimby system uses what calc system

A

long & away

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32
Q

paris system is ? distribution like ?

A

UNIFORM distrib like quimby

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33
Q

trocars are what used for what implants

A

hollow needles used for interstitial implants

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34
Q

anisotropy results when source construction causes ? dose distribution

A

non-uniform

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35
Q

mean life is the ? lifetime for decay of isotope

A

avg lifetime

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36
Q

exposure rate constant aka

A

gamma factor

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37
Q

objectives for implant dosimetry is to determine distribution of sources & type to provide ? dose distribution

A

optimum

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38
Q

autoradiograph determines

A

uniformity

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39
Q

full strength needles have ? mg Ra/cm

A

0.66 mg Ra/cm or 0.5

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40
Q

1/2 strength needles have ? mg Ra/cm

A

0.33 mg Ra/cm or 0.25

41
Q

activity of 1g of Ra-226 in Ci

A

0.988 Ci

42
Q

brachy shielding public continuous freq

A

0.1 rem or 1 mSv

43
Q

brachy shielding public infreq

A

0.5 rem or 5 mSv

44
Q

brachy shielding occupational

A

5 rem or 50 mSv

45
Q

brachy dose in any UNRESTRICTED are must not exceed

A

2 mrem in 1 hr

46
Q

threshold dose for hospitalized pts ? mCi

A

30 mCi

47
Q

dose before release of implant pts ? mSv per hr @ ? distance

A

< 0.5 mSv per hr @ 1 m

48
Q

waiting room adjacent to pt brachy room dose rate

A

below 2 mR/hr (2 mrem/hr) no action req’d

49
Q

ophthalmic plaque isotopes used

A
  • Co-60
  • I-125
  • Ru-106
  • Ir-192
50
Q

brain brachy isotope needs high/low activity?

A

high activity

51
Q

annual report given to workers who exceed ? % of occup limit

A

10%

52
Q

max leakage for walls, floors, etc ? mrem/wk

A

< 100

53
Q

occupational workers per week

A

100 mrem

54
Q

controlled area ? per hr or ? per wk

A

2 mrem/hr or 0.1 rem/wk

55
Q

radiation area ? mrem/hr

A

5

56
Q

brachy calib dosimetric protocol

A

TG-43

57
Q

gyn low dose implants point A ? cGy/hr

A

50-60 cGy/hr

58
Q

gyn low dose implants point B ? cGy/hr

A

18-20 cGy/hr

59
Q

LDR dose rate definition ? cGy/hr

A

40-200 cGy/hr

60
Q

MDR dose rate definition ? cGy/hr

A

200-1200 cGy/hr

61
Q

HDR dose rate definition ?cGy/hr

A

> 1200 cGy/hr

62
Q

Ra-226 to Cs-137 conversion

A

10mgRa= 25mCi

63
Q

cumulative implant dose formula

A

1.44 x t1/2 x Do

64
Q

shielding for stored radionuclides & generators reduce rad levels to < ? mrem/hr @ what distance

A

2 mrem/hr @ 1 m

65
Q

Cs-137 decays to what? by what kind of decay?

A

decays by B- to Ba-137

66
Q

Co-60 decays ? % per month

A

1%

67
Q

Co-60 decays to what by what kind of decay?

A

decays by B- to Ni-60

68
Q

Pd-103 is a ? emitter

A

pure gamma emitter

69
Q

Ir-192 is created by ?

A

neutron activation in reactor

70
Q

specific activity unit

A

Ci/g

71
Q

1 Bq = ? Ci

A

2.7 x 10^-11 Ci

72
Q

fletcher suite applicator produces a ? isodose distribution

A

pear shaped

73
Q

ovoids are stabilized with

A

packing which also pushes bladder & rectum away

74
Q

point A dose rate

A

50-60 cGy per hr

75
Q

point B dose rate

A

18-20 cGy per hr

76
Q

delclos allows for simultaneous tx of

A
  • uterus
  • vag walls
  • cervix
77
Q

packing for Burnett applicator is

A

at least 1.5cm

78
Q

vag cylinder can be used for what other type of tx

A

interstitial

79
Q

paterson parker provides dose of ? % within implanted area

A

+10% w/i implanted area (higher dose in periphery area)

80
Q

paterson parker uses ? distribution to produce ? distribution

A

NON-UNIFORM; UNIFORM

81
Q

multiple plane implants area should be reduced ? % for each uncrossed end

A

10%

82
Q

volume implants are used for ? implants where activity is evenly spread out inside an organ or structure

A

seed reduced 7.5% uncrossed ends

83
Q

in volume implants, dose is reduced by ? % at uncrossed ends

A

7.5

84
Q

quimby memorial system uses ? distribution of activity to give ? dose

A

UNIFORM distribution; NON-UNIFORM dose

85
Q

quimby prescribes ? arrangement of sources

A

uniform

86
Q

quimby results in ? dose distribution with high/low dose in ? region

A

NON-UNIFORM dose distrib w/HIGH dose in CENTRAL region

87
Q

quimby system used to plan what tx site

A

breast implants

88
Q

paris system is used for implants with removable long lines of ? isotope

A

Ir-192

89
Q

paris system reference dose is ? % of basal dose

A

85%

90
Q

paris system has ? % decrease on uncrossed ends

A

15%

91
Q

exposure rate constant is the exposure at ? distance from source

A

1 meter from radioactive source of known activity

92
Q

exposure rate constant is the exposure at ? distance from ? volume of Ra filtered by ? mm of platinum

A

1cm, 1mg or 1mCi, 0.5 mm

93
Q

leakage of sources has to be below

A

0.005 uCi

94
Q

isotope used frequently for brain

A

I-125 (40 mCi/seed)

95
Q

I-131 comes in what form

A

liquid or capsule

96
Q

how does body eliminate I-131

A

excreted in urine

97
Q

I-131 emits?

A

emits gamma & beta

98
Q

Sr-90/Y-90 isotopes are loose/sealed

A

sealed

99
Q

Sr-90/Y-90 emits

A

emits only low E beta particles

Dosimetry (53 decks)

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