Brachytherapy Quiz

Question 1

Iridium-192 (Ir-192) half life

Answer 1

73.8 days

Question 2

Ir-192 clinical use

Answer 2

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

Question 3

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

Answer 3

Specific activity

Question 4

High activity/dose in a small volume

Answer 4

High specific activity

Question 5

Iodine-131 (I-131) clinical use

Answer 5

Thyroid ablation uptakes iodine

Question 6

Radon-222 (Rn-222) half life

Answer 6

3.83 days

Question 7

Daughter of radium-226 (Ra-226)

Answer 7

Radon-222 (Rn-222)

Question 8

First source

Answer 8

Radium-226 (Ra-226)

Question 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

Answer 9

Milligram radium equivalent (mgRaeq)

Question 10

Cesium-137 (Cs-137) clinical use

Answer 10

LDR intracavitary and interstitial

Question 11

Cs-137 half life

Answer 11

30 years

Question 12

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

Answer 12

Dual: 1.17 MeV and 1.33 MeV
Average: 1.25 MeV

Question 13

3 clinical uses of Co-60 and why

Answer 13

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

Question 14

Co-60 Dmax

Answer 14

0.5 cm

Question 15

2 prostate seed sources

Answer 15

Iodine-125 (I-125)

Palladium-103 (Pd-103)

Question 16

Iodine-125 (I-125) half life

Answer 16

59.6 days

Question 17

Palladium-103 (Pd-103) half life

Answer 17

17 days

Question 18

2 brachytherapy (brachy) seed arrangements

Answer 18

Linear

Planar

Question 19

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

Answer 19

Milligram-hour (mghr)

Question 20

Mghr _______ with distance from source

Answer 20

Increases

Question 21

2 source types

Answer 21

Point

Linear

Question 22

4 HDR treatments

Answer 22

Breast
GYN
Prostate
Interstitial STS and esophageal

Question 23

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

Answer 23

Savi applicator

Question 24

2 GYN HDR applicators

Answer 24

Vaginal cylinder

Tandem and ovoids (T&O): cervical

Question 25

HDR prostate source

Answer 25

Iridium-192 (Ir-192)

Question 26

1 mCi = ___ disintegration/sec

Answer 26

1 disintegration/sec

Question 27

Activity after time (At) formula

Answer 27

At = Aoe^-(0.693/T1/2)(t) ``` Ao = original activity T1/2 = half life t = time ```

Question 28

Rate between radium and current source

Answer 28

Exposure rate constant (Γ)

Question 29

Γ unit

Answer 29

Rcm^2/mCihr

Question 30

Exposure rate (X) follows _______

Answer 30

Inverse square law (ISL)

Question 31

Exposure rate (X) formula

Answer 31

X = ΓA/r^2 r = radius/distance

Question 32

Radium conversion/mgRaeq equation

Answer 32

Γ1A1 = Γ2A2

Question 33

Number of seeds (n) equation

Answer 33

AL = n x s ``` AL = active length s = s[acomg ```

Question 34

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

Answer 34

Fornices Vaginal canal 3

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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

Answer 37

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

Question 38

3 ovoid sizes

Answer 38

2 cm 2.5 3 cm

Question 39

Number of half lives (n) formula

Answer 39

(1/2)^n = At/Ao

Question 40

3 dose rate classifications

Answer 40

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

Question 41

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

Answer 41

Secular equilibrium

Question 42

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

Answer 42

Transient equilibrium

Question 43

Mean life (Ta) formula

Answer 43

Ta = 1.44(T1/2)

Question 44

Technetium-99 clinical use

Answer 44

PET scan (transient equilibrium)

Question 45

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

Answer 45

Zofigo

Question 46

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

Answer 46

Fludeoxyglucose (FDG-18)

Question 47

Breast initial and boost dose

Answer 47

Initial: 45-50 Gy Boost: 1000 cGy

Question 48

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

Answer 48

15 fractions x 287 cGy/day = 4005 cGy

Question 49

Treatment time _______ as Co-60 decreases

Answer 49

Increases

Question 50

Why do prostate sources usually have pointed ends?

Answer 50

To better stick to tissue

Question 51

Why are brachy dose distributions usually anisotropic?

Answer 51

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

Question 52

Non-isotropic, not equal in all directions

Answer 52

Anisotropic

Question 53

Ra-226 half life

Answer 53

1626 years

Question 54

Co-60 half life

Answer 54

5.26 years

Question 55

I-131 half life

Answer 55

8.06 days

Question 56

Decay constant formula

Answer 56

0.693/T1/2