Brachytherapy Quiz Flashcards Preview

RAD 400 > Brachytherapy Quiz > Flashcards

Flashcards in Brachytherapy Quiz Deck (56)
Loading flashcards...
1

Iridium-192 (Ir-192) half life

73.8 days

2

Ir-192 clinical use

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

3

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

Specific activity

4

High activity/dose in a small volume

High specific activity

5

Iodine-131 (I-131) clinical use

Thyroid ablation uptakes iodine

6

Radon-222 (Rn-222) half life

3.83 days

7

Daughter of radium-226 (Ra-226)

Radon-222 (Rn-222)

8

First source

Radium-226 (Ra-226)

9

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

Milligram radium equivalent (mgRaeq)

10

Cesium-137 (Cs-137) clinical use

LDR intracavitary and interstitial

11

Cs-137 half life

30 years

12

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

Dual: 1.17 MeV and 1.33 MeV
Average: 1.25 MeV

13

3 clinical uses of Co-60 and why

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

14

Co-60 Dmax

0.5 cm

15

2 prostate seed sources

Iodine-125 (I-125)
Palladium-103 (Pd-103)

16

Iodine-125 (I-125) half life

59.6 days

17

Palladium-103 (Pd-103) half life

17 days

18

2 brachytherapy (brachy) seed arrangements

Linear
Planar

19

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

Milligram-hour (mghr)

20

Mghr _______ with distance from source

Increases

21

2 source types

Point
Linear

22

4 HDR treatments

Breast
GYN
Prostate
Interstitial STS and esophageal

23

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

Savi applicator

24

2 GYN HDR applicators

Vaginal cylinder
Tandem and ovoids (T&O): cervical

25

HDR prostate source

Iridium-192 (Ir-192)

26

1 mCi = ___ disintegration/sec

1 disintegration/sec

27

Activity after time (At) formula

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

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

28

Rate between radium and current source

Exposure rate constant (Γ)

29

Γ unit

Rcm^2/mCihr

30

Exposure rate (X) follows _______

Inverse square law (ISL)

31

Exposure rate (X) formula

X = ΓA/r^2

r = radius/distance

32

Radium conversion/mgRaeq equation

Γ1A1 = Γ2A2

33

Number of seeds (n) equation

AL = n x s

AL = active length
s = s[acomg

34

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

Fornices
Vaginal canal
3

35

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

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

36

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

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

37

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

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

3 ovoid sizes

2 cm
2.5
3 cm

39

Number of half lives (n) formula

(1/2)^n = At/Ao

40

3 dose rate classifications

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

41

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

Secular equilibrium

42

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

Transient equilibrium

43

Mean life (Ta) formula

Ta = 1.44(T1/2)

44

Technetium-99 clinical use

PET scan (transient equilibrium)

45

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

Zofigo

46

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

Fludeoxyglucose (FDG-18)

47

Breast initial and boost dose

Initial: 45-50 Gy
Boost: 1000 cGy

48

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

15 fractions x 287 cGy/day = 4005 cGy

49

Treatment time _______ as Co-60 decreases

Increases

50

Why do prostate sources usually have pointed ends?

To better stick to tissue

51

Why are brachy dose distributions usually anisotropic?

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

52

Non-isotropic, not equal in all directions

Anisotropic

53

Ra-226 half life

1626 years

54

Co-60 half life

5.26 years

55

I-131 half life

8.06 days

56

Decay constant formula

0.693/T1/2