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Brachytherapy Quiz Flashcards

1
Q

Iridium-192 (Ir-192) half life

A

73.8 days

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2
Q

Ir-192 clinical use

A

“Grain of rice” high dose rate (HDR) in remote afterloader for GYN and prostate interstitial implants; high specific activity (A) (HDR increases specific A)

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3
Q

Activity (A) per volume/unit of mass a radioactive material that dictates the total A a small source can have (Ci/g)

A

Specific activity

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4
Q

High activity/dose in a small volume

A

High specific activity

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5
Q

Iodine-131 (I-131) clinical use

A

Thyroid ablation uptakes iodine

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6
Q

Radon-222 (Rn-222) half life

A

3.83 days

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7
Q

Daughter of radium-226 (Ra-226)

A

Radon-222 (Rn-222)

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8
Q

First source

A

Radium-226 (Ra-226)

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9
Q

Amount of radium substitute source that gives the same output as a 1 mg Ra source encapsulated in 0.5 mm platinum (Pt) in the same output measurement geometry

A

Milligram radium equivalent (mgRaeq)

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10
Q

Cesium-137 (Cs-137) clinical use

A

LDR intracavitary and interstitial

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11
Q

Cs-137 half life

A

30 years

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12
Q

Cobalt-60 (Co-60) dual and average energies

A

Dual: 1.17 MeV and 1.33 MeV
Average: 1.25 MeV

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13
Q

3 clinical uses of Co-60 and why

A

HDR intracavitary because it has a higher energy than other sources
Machine testing and calibration because it is known how much it decays
EBRT source because its Dmax is 0.5 cm

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14
Q

Co-60 Dmax

A

0.5 cm

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15
Q

2 prostate seed sources

A

Iodine-125 (I-125)

Palladium-103 (Pd-103)

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16
Q

Iodine-125 (I-125) half life

A

59.6 days

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17
Q

Palladium-103 (Pd-103) half life

A

17 days

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18
Q

2 brachytherapy (brachy) seed arrangements

A

Linear

Planar

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19
Q

How long the beam is on and how long it takes to deliver dose

A

Milligram-hour (mghr)

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20
Q

Mghr _______ with distance from source

A

Increases

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21
Q

2 source types

A

Point

Linear

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22
Q

4 HDR treatments

A

Breast
GYN
Prostate
Interstitial STS and esophageal

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23
Q

HDR “egg whisk” surgically inserted in seroma cavity of breast once a day for five days

A

Savi applicator

24
Q

2 GYN HDR applicators

A

Vaginal cylinder

Tandem and ovoids (T&O): cervical

25
Q

HDR prostate source

A

Iridium-192 (Ir-192)

26
Q

1 mCi = ___ disintegration/sec

A

1 disintegration/sec

27
Q

Activity after time (At) formula

A

At = Aoe^-(0.693/T1/2)(t)

Ao = original activity
T1/2 = half life
t = time
28
Q

Rate between radium and current source

A

Exposure rate constant (Γ)

29
Q

Γ unit

A

Rcm^2/mCihr

30
Q

Exposure rate (X) follows _______

A

Inverse square law (ISL)

31
Q

Exposure rate (X) formula

A

X = ΓA/r^2

r = radius/distance

32
Q

Radium conversion/mgRaeq equation

A

Γ1A1 = Γ2A2

33
Q

Number of seeds (n) equation

A

AL = n x s

AL = active length
s = s[acomg
34
Q

Ovoids in _______, tandem in __________ (usually ___ dwell points

A

Fornices
Vaginal canal
3

35
Q

T&O along distance at point 1, 2, 3, 4, and 5

A

1: 3
2: 1
3: 1
4: 3
5: 0

36
Q

T&O away distance at point 1, 2, 3, 4, and 5

A

1: 2
2: 2
3: 2
4: 4
5: 3

37
Q

How is an implant’s effective area affected if both ends are closed, 1 is open, or 2/each end is open

A

Both: same as actual area
1 open: area reduced by 10% = (area)(0.9)
2 open: area reduced by another 10% = (area)(0.81)

38
Q

3 ovoid sizes

A

2 cm
2.5
3 cm

39
Q

Number of half lives (n) formula

A

(1/2)^n = At/Ao

40
Q

3 dose rate classifications

A

HDR: 12 or more Gy/hr
MDR: 12-2 Gy/hr
LDR: under 2 Gy/hr

41
Q

Parent’s half life is much greater than the daughter’s; ex: Ra (1626 yr)&raquo_space; Rn (3.83 days)

A

Secular equilibrium

42
Q

Parent’s half life is slightly longer than daughter’s; about 10 times
Ex: Mo-99 (67 hr) > Tc-99m (6.7 hr)

A

Transient equilibrium

43
Q

Mean life (Ta) formula

A

Ta = 1.44(T1/2)

44
Q

Technetium-99 clinical use

A

PET scan (transient equilibrium)

45
Q

Brand name of radium (isotope) for bone mets, absorbed like calcium

46
Q

Injection that mimics sugar uptake to see highly metabolic areas
False positive areas: brain, heart apex, bladder, etc.

A

Fludeoxyglucose (FDG-18)

47
Q

Breast initial and boost dose

A

Initial: 45-50 Gy
Boost: 1000 cGy

48
Q

Canadian breast protocol (higher daily dose and less total dose)

A

15 fractions x 287 cGy/day = 4005 cGy

49
Q

Treatment time _______ as Co-60 decreases

50
Q

Why do prostate sources usually have pointed ends?

A

To better stick to tissue

51
Q

Why are brachy dose distributions usually anisotropic?

A

Usually more shielding on ends of source so more filtration on ends and isodoses closer to end

52
Q

Non-isotropic, not equal in all directions

A

Anisotropic

53
Q

Ra-226 half life

A

1626 years

54
Q

Co-60 half life

A

5.26 years

55
Q

I-131 half life

56
Q

Decay constant formula

A

0.693/T1/2

RAD 400 (4 decks)

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