Linac Faults

Question 1

What must you consider regarding patient safety?

Answer 1

• Is patient comfortable
• Is it possible with patient on the couch
• Is patient wearing uncomfortable immobilisation equipment

Question 2

What if it is a gun fault?

Answer 2

• No gun, no electrons, linac will absolutely not work
• Where is the gun, what else will be affected, what other components?
• Not easy to get a new gun, maybe ONE spare
• Replacing the gun is a major task as it disrupts multiple parts of the linac and all must be checked
• Machine may be out of use for up to two days

Question 3

What if it is a vacuum fault?

Answer 3

• ion pumps must be switched off before looking for vacuum fault.
• Must then check each seal and find the leak.

Question 4

What if there is a steering fault?

Answer 4

• If the electron beam hits the target offset, it will produce a beam profile but they will be incorrect
• A monitoring system will stop the machine (ion chamber)
• Physics and engineers will need to be consulted