11. Materials for barriers & Neutron Protection

What materials are barriers in a vault room usually made of?

concrete cuz its cheaper (and also absorbs neutrons cuz it’s made out of water)

Recap: neutrons can be produced at energies around 10 MV due to photodisintegration

If space is at a premium, what materials can you use to make the Vault instead of concrete?

lead or steel, but it is more expensive

What is the primary barrier for orthovoltage made out of?

3/8 inch of lead sheet (4x lead sheet thickness of lead window)

Same thickness of a material for KV x-rays (diagnostic or therapy) 

Traditionally, on what floor is a radiation therapy room located in the hospital?

Ground floor or basement

Traditionally, the RTT vault Room Design is what?

a Maze

Why are RTT vault rooms designed as a maze?

Dramatically reduces shielding needs at the door

The maze should create at least __ scatters (#)

2 scatters

Lead shielding at the door if the room is designed as a maze should be about __ thick

6 mm (~ 3/8 inch) lead

Room design should be undertaken by a team (designing team) that should include about 6 people:

1. hospital administrator - heads the project

2. architect

3. physicist

4. department director

5. chief tech

6. equipment rep

Neutron protection is needed for energies greater than __

10 MV

Neutron contamination peaks at about ___ energy, and then levels off after that

20 MV

What is the most practical material for neutron contamination?

Concrete (cuz the water absorbs neutrons)

Door shielding for neutrons. What materials are used?

Most common material: Boron or Polyethylene

You still need: lead or steel for x-ray protection