Therapy

Question 1

What is the half-life of Co-60?

Answer 1

5.26 years

Question 2

What is the decay energy of Co-60?

Answer 2

1.25 MeV

Question 3

What is the depth of dmax for a Co-60 beam?

Answer 3

0.5 cm

Question 4

What is dmax for a 6MV beam?

Answer 4

1.5 cm

Question 5

What is dmax for a 10 MV beam?

Answer 5

2.5 cm

Question 6

What is dmax for an 18 MV beam?

Answer 6

3.2 cm

Question 7

How much less dense is lung than water?

Answer 7

~1/3

Question 8

How much more dense is bone than water?

Answer 8

~2x

Question 9

What does a proton beam transport system consist of?

Answer 9

Bending magnets, focusing magnets, diagnostic measurement tools

Question 10

What magnetic field is used in cyclotron-based proton accelerators?

Answer 10

2-4 Tesla

Question 11

What is actually accelerated by a cyclotron in a cyclotron-based proton system?

Answer 11

H2+ ions (2 protons + 1 electron)

Question 12

How do you extract the protons from the accelerator?

Answer 12

a process called stripping. You run them through a thin (usually graphite) foil, which removes the excess electron

Question 13

What is the klystron sitting in in a linac?

Answer 13

oil - for cooling

Question 14

What fills the waveguide and why?

Answer 14

sulfer hexafluoride (SF6) to prevent arcing

Question 15

What are some of the major annual QA tests performed on a linac?

Answer 15

Safety, Mechanicals, Visual (ODI, lasers), Film (star shot, light vs rad), scanning (PDD, flatness, symmetry), Chamber (output, wedge/tray factors, MU linearity, dose rate, TG51)