Topic 10 QA Radiation Protection

Question 1

how often must you replace an HDR source?

Answer 1

There is no regulation.

Question 2

how often to check the CBCT phantom and check shifts?

Answer 2

Daily

Question 3

How often to check image quality for MV and kV?

Answer 3

Monthly

Question 4

How often to check for geometric accuracy?

Answer 4

Monthly

Question 5

How often to check for CBCT shifts?

Answer 5

Monthly

Question 6

frequency of picket fence test?

Answer 6

Weekly

Question 7

Is external scatter greater with metal blocks or with static MLCs?

Answer 7

metal blocks

Question 8

What is a TVL? how much will 3 TVLs decrease the dose?

Answer 8

A tenth value layer. 
3 TVLs will decrease dose by 0.1^3
Or
in order to reduce the dose by a factor of 5, 
10^n =5. or n=log10(5)

Question 9

Does scatter or leakage increase with IMRT over 3D?

Answer 9

leakage, due to increased MUs

Question 10

in FMEA (failure mode effects analysis, what is prioritized?

Answer 10

severity
frequency
detectability

Question 11

to release a patient with a permanent implant what is the maximum allowable dose to another individual?

Answer 11

5 mSv

Question 12

Who certifies the training needed to receive radioactive packages?

Answer 12

Dept of Transportation

Question 13

Sv is the SI unit of _____.

Answer 13

Equivalent dose

Just like Gy, it is J/kg

Question 14

What is not suitable for in vivo dosimetry?

• Diodes
• TLDs
• OSLDs
• MOSFETs
• Ion Chambers

Answer 14

Ion chambers - they require high voltage

Question 15

What is the most accurate way to measure surface dose?

Answer 15

Extrapolation chamber

Question 16

What measures dosimetry for electron beams <10 MeV?

Answer 16

Parallel plate chambers

Question 17

What is a parallel plate chamber used for?

Answer 17

dosimetry for electron beams <10 MeV
surface dose for photons
depth dose for photon/electron beams

Question 18

How often must survey meters be sent for calibration?

Answer 18

1 year

Question 19

how often must therapy dosimeters (chambers used to calibrate therapy beams) be sent for calibration?

Answer 19

2 years

Question 20

AAP recommends brachy souces are specifies in terms of their _____.

Answer 20

Air kerma strength

Question 21

How often are brachy souces leak tested?

Answer 21

q6 months

Question 22

How often/ who calibrates the Farmer Chamber?

Answer 22

Annually, in-house physicist

Question 23

How often do well chambers need to be calibrated?

Answer 23

every 2 years

Question 24

WHat energy beam produces unwanted neutrons?

Answer 24

higher energies like 15 MV

Question 25

What dosimeter does not have to be calibrated?

Answer 25

Free-air ionization chamber, this is an absolute dosimeter aka the primary standard

Question 26

What checks have to be performed monthly for the planar MV imaging system?

Answer 26

collision interlocks (to prevent colliding with patient)

Question 27

What tests MLC location?

Answer 27

picket fence test

Question 28

What is the cumulative dose limit for a radiation worker?

Answer 28

10 mSv * age

Question 29

Max dose allowed to the eye for a radiation worker

Answer 29

150 mSv or 0.15 Sv

non-stoichastic, so there is a threshold dose