Radiotherapy QA Flashcards
What are the mechanical uncertainties that come from a Linac?
- Jaw calibration
- Light-field coincidence
- Laser alignment
- Collimator rotation
- Gantry rotation and sag
- Table movements (3-axes and rotation)
What is the suspend tolerance for a Linac LASER?
+/- 2mm
What is the suspend tolerance for Gantry Rotation?
+/- 0.5deg
What is the suspend tolerance for collimator rotation?
+/- 0.5deg
What is the suspend tolerance for couch movements?
+/- 2mm
What is the suspend tolerance for couch rotation?
+/- 0.5deg
What is the suspend tolerance for radiation field size (jaw calibration)?
+/- 2mm (field size at isocentre)
What is the suspend tolerance for light field size?
+/- 2mm (field size at isocentre)
What are the dosimetric uncertainties that come from a Linac?
- Radiation output
- Beam energy
- Beam flatness and symmetry
- Dose delivery stability
What is the suspend tolerance for radiation output (absorbded dose to water per MU)?
+/- 3%
What is the suspend tolerance for beam energy (TPR-20/10)?
+/- 1.5%
What is the suspend tolerance for Beam flatness and symmetry?
+/- 3% basline profiles
What is the suspend tolerance for Dose delivery stability (radiation output with gantry rotation)?
+/- 2.5%
What is the suspend tolerance for Dose delivery stability (Radiation output with MUs)?
+/- 2%
What checks are likely to be part of daily QA?
- Output constancy
- Absolute dose (weekly)
- Safety interlocks
- LASER alignment
- Light-field and crosswire set-up