Design of Treatment Facilities

Question 1

What are the principles of radiation protection in radiotherapy treatment facility designs?

Answer 1

Time
Distance - Restrict access, large room
Shielding - Physical barriers, mazes/shielded doors, lead glass

Question 2

What shielding material is used in RT treatment facilities and why (advantages and disadvantages)?

Answer 2

(High density) Concrete - cheap and easy to source, but bulky (~2m for primary barriers)

Steel - heavy, expensive but more compact, can be used to enhance loacalised areas

Lead - heavy, toxic, expensive but very compact, good for low energy - rarely in RT

Question 3

What design features are there in a manual afterloading brachytherapy treatment facility?

Answer 3

Not particular room shielding
Movable lead shields
Consider time of staff and visitors present
For I-125 - patient should be enough shielding

Question 4

What design features are there in a HDR brachytherapy treatment facility?

Answer 4

A high dose rate unit will need a dedicated protected room, suitable for the energy of the sources used.
Thick concrete walls, maze entrance
Maze needs careful design (radiation not collimated)
Control desk outside treatment room
Will be a “controlled area” under the regulations
Radiation warning lights – independent of machine
Interlocked barrier at room entrance(s)
Audible alarm when source exposed
Simple scatter maze
High density concrete walls
Interlocked doors
Consider adjacent areas

Concrete walls (0.5m)
Small maze, door with Lead lining

Question 5

What design features are there in a kV treatment facility?

Answer 5

300-50kV energy domain
Beam may not be constrained in direction
Standard wall materials can be used
Lead is very efficient as an additional shielding material
Lead glass windows can be used
For 50kV machines can consider local operation – but generally easier to work behind a shield

Concrete walls (0.2m), sometimes additional lead

Door with Lead lining

Question 6

What design features are there in a proton treatment facility?

Answer 6

Can use beam scanning or scattering techniques
Big radiation protection issues:
Neutrons produced
Activation of materials
Cyclotron hall barriers 3-5m concrete. Gantry rooms 2m concrete

Maze with optional neutron door

Question 7

What design features are there in a linac treatment facility?

Answer 7

Primary/Secondary Barriers
(1-3m concrete)

Maze or v. large motorised door