60. RADIOTHERAPY: LINAC COMPONENTS

Question 1

1. Does this image make sense?

Answer 1

• yes

Question 2

2. How are LINACs often mounted?

Answer 2

• they are mounted isocentrically
• this means that all the beams that are being used in
  the radiation treatment
• all have a common focus point

Question 3

3. What 5 major and distinct sections of the machine are the Operational Systems distributed over?

Answer 3

1. the Gantry
2. the Gantry Stand (Support)
3. Modulator Cabinet
4. Patient Treatment Table
5. Control Console

Question 4

4. What is the Control Console?

Answer 4

• this is found outside the Treatment room
• the operator is responsible for this

Question 5

5. What is the advantage of the Gantry Stand?

Answer 5

• it maintains a constant temprature

Question 6

6. Does this image make sense?

Answer 6

• yes

ELECTRON BEAM:
- this is where the electrons are accelerated towards the
target

IONISATION CHAMBER:
- this measures the dose
- it indicates the amount of X-Rays

COLLIMATORS:
- this changes the diverging light coming from a point
source
- into a parallel beam

FILTERS ON CAROUSEL:
- this produces a flat radiation beam

Question 7

7. What does this image show?

Answer 7

• this is the Treatment Head

FLATTENING FILTER:
- flattens the beam

SCATTERING FOILS:
- make the electric field more uniform

DUAL IONISATION CHAMBER:
- measures the dose

Question 8

8. What does the length of the Accelerating Waveguide depend on?

Answer 8

• the final electron kinetic energy

Question 9

9. What are the lengths that the Accelerating Waveguide ranges from?

Answer 9

• it ranges from roughly 30 cm at 4 MeV
• to roughly 150 cm at 25 MeV

Question 10

10. What 6 classes are the main beam forming components of the modern medical LINAC grouped into?

Answer 10

1. Injection System
   (Electron Gun)
2. RF Power Generation System
3. Accelerating Waveguide
4. Auxiliary System
   (Shielding, Vacuum Pump, Cooling System)
5. Beam Transport System
6. Beam Collimation Systems
   (Beam Monitoring Systems)