General Brachytherapy Flashcards
(99 cards)
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
2
Q
Ra/daughter equilibrium takes how long to reach?
A
30 days
3
Q
uniform sources have same concentration of radioactivity through entire ?
A
length
4
Q
Cs-137 decays ?% in 6 months
A
1%
5
Q
Cs-137 used for what implants?
A
gyn
6
Q
Pd-103 decays by ? to ?
A
by e- capture to Rh-103
7
Q
P-32 t1/2
A
14.3 days
8
Q
P-32 used for what implants
A
intravascular & peritoneum
9
Q
Ir-192 decays ? % per day
A
1%
10
Q
Au-198 decays by what to what
A
B- to Hg-198
11
Q
I-125 emits what
A
pure gamma emitter
12
Q
Sr-90 emits what
A
pure beta emitter
13
Q
activity aka
A
- strength of source
- rate of decay
- # of nuclei decaying per sec
14
Q
decay constant incr then activity ?
A
incr; directly prop
15
Q
decay constant is the total # ? that decay per unit time
A
total # of atoms that decay per unit of time
16
Q
t1/2 incr then overall activity ?
A
decr; inv prop; decay decr
17
Q
average E is the avg value of ? from each isotope
A
all emitted photons from each isotope
18
Q
specific activity is the activity per unit ? of radioactive material
A
mass
19
Q
specific activity decr then activity per gram ?
A
decr; directly prop
20
Q
Ci is ? dps
A
3.7 x 10^10 dis/sec
21
Q
Bq is ? dps
A
1 dis/sec
22
Q
fletcher suite applicator is made up of ?
A
- uterine tandem
- cervical colpostats (ovoids)
- capsules for uterine
23
Q
heymans capsules are used when ? still intact
A
uterus
24
Q
delclos is used for ? afterloading
A
uterine-vag
25
burnett applicator is use for tx of ?
tx vaginal tissues
26
Ra-226 dose distrib based on
calcs
27
square or rectangular implants aka
planar implant
28
multiple plane implants are spaced how far apart
1 cm apart & parallel
29
with volume implants, more than ? planes of sources are used
2
30
quimby/memorial system is similar to ?
paterson
31
quimby system uses what calc system
long & away
32
paris system is ? distribution like ?
UNIFORM distrib like quimby
33
trocars are what used for what implants
hollow needles used for interstitial implants
34
anisotropy results when source construction causes ? dose distribution
non-uniform
35
mean life is the ? lifetime for decay of isotope
avg lifetime
36
exposure rate constant aka
gamma factor
37
objectives for implant dosimetry is to determine distribution of sources & type to provide ? dose distribution
optimum
38
autoradiograph determines
uniformity
39
full strength needles have ? mg Ra/cm
0.66 mg Ra/cm or 0.5
40
1/2 strength needles have ? mg Ra/cm
0.33 mg Ra/cm or 0.25
41
activity of 1g of Ra-226 in Ci
0.988 Ci
42
brachy shielding public continuous freq
0.1 rem or 1 mSv
43
brachy shielding public infreq
0.5 rem or 5 mSv
44
brachy shielding occupational
5 rem or 50 mSv
45
brachy dose in any UNRESTRICTED are must not exceed
2 mrem in 1 hr
46
threshold dose for hospitalized pts ? mCi
30 mCi
47
dose before release of implant pts ? mSv per hr @ ? distance
< 0.5 mSv per hr @ 1 m
48
waiting room adjacent to pt brachy room dose rate
below 2 mR/hr (2 mrem/hr) no action req'd
49
ophthalmic plaque isotopes used
- Co-60
- I-125
- Ru-106
- Ir-192
50
brain brachy isotope needs high/low activity?
high activity
51
annual report given to workers who exceed ? % of occup limit
10%
52
max leakage for walls, floors, etc ? mrem/wk
< 100
53
occupational workers per week
100 mrem
54
controlled area ? per hr or ? per wk
2 mrem/hr or 0.1 rem/wk
55
radiation area ? mrem/hr
5
56
brachy calib dosimetric protocol
TG-43
57
gyn low dose implants point A ? cGy/hr
50-60 cGy/hr
58
gyn low dose implants point B ? cGy/hr
18-20 cGy/hr
59
LDR dose rate definition ? cGy/hr
40-200 cGy/hr
60
MDR dose rate definition ? cGy/hr
200-1200 cGy/hr
61
HDR dose rate definition ?cGy/hr
> 1200 cGy/hr
62
Ra-226 to Cs-137 conversion
10mgRa= 25mCi
63
cumulative implant dose formula
1.44 x t1/2 x Do
64
shielding for stored radionuclides & generators reduce rad levels to < ? mrem/hr @ what distance
2 mrem/hr @ 1 m
65
Cs-137 decays to what? by what kind of decay?
decays by B- to Ba-137
66
Co-60 decays ? % per month
1%
67
Co-60 decays to what by what kind of decay?
decays by B- to Ni-60
68
Pd-103 is a ? emitter
pure gamma emitter
69
Ir-192 is created by ?
neutron activation in reactor
70
specific activity unit
Ci/g
71
1 Bq = ? Ci
2.7 x 10^-11 Ci
72
fletcher suite applicator produces a ? isodose distribution
pear shaped
73
ovoids are stabilized with
packing which also pushes bladder & rectum away
74
point A dose rate
50-60 cGy per hr
75
point B dose rate
18-20 cGy per hr
76
delclos allows for simultaneous tx of
- uterus
- vag walls
- cervix
77
packing for Burnett applicator is
at least 1.5cm
78
vag cylinder can be used for what other type of tx
interstitial
79
paterson parker provides dose of ? % within implanted area
+10% w/i implanted area (higher dose in periphery area)
80
paterson parker uses ? distribution to produce ? distribution
NON-UNIFORM; UNIFORM
81
multiple plane implants area should be reduced ? % for each uncrossed end
10%
82
volume implants are used for ? implants where activity is evenly spread out inside an organ or structure
seed **reduced 7.5% uncrossed ends**
83
in volume implants, dose is reduced by ? % at uncrossed ends
7.5
84
quimby memorial system uses ? distribution of activity to give ? dose
UNIFORM distribution; NON-UNIFORM dose
85
quimby prescribes ? arrangement of sources
uniform
86
quimby results in ? dose distribution with high/low dose in ? region
NON-UNIFORM dose distrib w/HIGH dose in CENTRAL region
87
quimby system used to plan what tx site
breast implants
88
paris system is used for implants with removable long lines of ? isotope
Ir-192
89
paris system reference dose is ? % of basal dose
85%
90
paris system has ? % decrease on uncrossed ends
15%
91
exposure rate constant is the exposure at ? distance from source
1 meter from radioactive source of known activity
92
exposure rate constant is the exposure at ? distance from ? volume of Ra filtered by ? mm of platinum
1cm, 1mg or 1mCi, 0.5 mm
93
leakage of sources has to be below
0.005 uCi
94
isotope used frequently for brain
I-125 (40 mCi/seed)
95
I-131 comes in what form
liquid or capsule
96
how does body eliminate I-131
excreted in urine
97
I-131 emits?
emits gamma & beta
98
Sr-90/Y-90 isotopes are loose/sealed
sealed
99
Sr-90/Y-90 emits
emits only low E beta particles
