Design of Treatment Facilities Flashcards
(21 cards)
What are the 5 categories in the Hierarchy of controls?
Describe 1 way to reduce the time an employee is exposed to radiation in radiotherapy
Permit to work
Describe 2 ways to reduce the distance an employee is from radiation in radiotherapy
Restricting access
Large rooms
Describe 3 way to sheild an employee from radiation in radiotherapy
Physical barriers
Maze/shielded doors
Lead glass
State the 4 commonly used materials that shield radiation facilities and their applications
- Concrete: high-energy (radiotherapy) facilities
- High density concrete: high-energy (radiotherapy) facilities
- Steel: enhancing linac bunkers
- Lead: low-energy (diagnostic) facilities
Describe the typical design of a linear accelerator bunker
- Maze
- Primary barrier
- Secondary barrier
(1-3m of concrete)
What shielding is required for a Cyberknife?
An all-round primary barrier
What shielding is required for a TomoTherapy/Halycon unit?
The unit has integral shielding so only secondary barriers are required
Describe the main radiation protection requirements for a brachytherapy suite (with manual afterloading)
- Moveable lead shields
- Timers to calculate the time staff/visitors can be present
Describe the main radiation protection requirements for a HDR brachytherapy suite
- Dedicated, protected room designated as a ‘controlled area’ (suitable for the source energies used)
- Thick concrete walls (0.5m)
- Carefully designed maze entrance (as the radiation is not collimated)
- Radiation warning lights (independent of the machine)
- Interlocked barrier at room entrance(s)
- Audible alarm when the source is exposed
- Control desk outside of the treatment room
Describe the main radiation protection requirements for an orthovoltage (therapeutic kV) room
- For walls, standard materials can be used (0.2m concrete)
- Additional lead shielding for doors
- Lead glass windows
What are the 2 main radiation protection issues for proton therapy?
- Neutron production
- Activation of materials
Decribe the main radiation protection requirements for proton beam therapy
- Cyclotron hall barriers 3-5m of concrete
- Gantry rooms 2m of concrete
- Maze with optional neutron door
What is the ICRP radition weighting factor for photons?
1
The radiation weighting factor for neutrons changes with _______.
Energy
What is the radiation weighting factor for protons?
2
When should radiation shielding be tested?
As early as possible after new equipment is installed or following any structural changes to a bunker.
What are the typical energies of a linac beam?
6-15 MV
What are the typical energies of HDR brachytherapy?
380 keV
What are the typical energies of an orthovoltage beam?
50-300 kV
What are the typical energies of proton therapy?
62-250 MeV
