RTonc.site the Exam Preparation: LINAC QA
Task Group 142 report: Quality assurance of medical accelerators 2009
LINAC QA Parameters & Tolerances Reference
Study Guide • Reference Link: https://www.aapm.org/meetings/amos2/pdf/48-14355-85222-897.pdf
Watermarked Study Material — RTonc.site
Most Common and Important
| Parameter | Tolerance / Requirement |
|---|---|
| Laser | ±2 mm |
| ODI | ±2 mm |
| Couch movement / Jaw position | ±2 mm |
| Couch / Gantry / Collimator angle | ±1° |
| MLC leaf position | ±1 mm |
| Light vs radiation field | ±2 mm |
| Daily / Monthly / Annual Output | ±3% / ±2% / ±1% |
| Imaging coincidence | ±2 mm |
| SRS isocenter vs Conventional | ≤1 mm vs ≤2 mm diameter |
Daily QA
| Parameter | 3DCRT | IMRT/VMAT | SRS/SBRT |
|---|---|---|---|
| Output constancy | ±3% | ±3% | ±2% |
| Laser localization | ±2 mm | ±2 mm | ±1 mm |
| ODI | ±2 mm | ±2 mm | ±1 mm |
| Imaging & treatment coincidence | ±2 mm | ±2 mm | ±1 mm |
| Door interlock / Beam-on | Functional | ||
| Audiovisual monitor | Functional | ||
Monthly QA
| Parameter | Tolerance / Requirement |
|---|---|
| Output constancy (X-ray / Electron) | ±2% |
| Beam flatness & symmetry | ±2% |
| Laser alignment / ODI / Cross-hair | ±2 mm |
| Light vs radiation field / Jaw position | ±2 mm |
| Couch vertical/longitudinal/lateral | ±2 mm |
| Couch / Gantry / Collimator rotation | ±1° |
Mechanical QA
| Parameter | Tolerance / Requirement |
|---|---|
| Laser / ODI / Cross-hair | ±2 mm |
| Light & Radiation field size / Coincidence | ±2 mm |
| Jaw calibration / Couch motion | ±2 mm |
| Gantry / Collimator / Couch indicators | ±1° |
MLC QA
| Parameter | Tolerance / Requirement |
|---|---|
| Leaf position accuracy & reproducibility | ±1 mm |
| Dynamic leaf positioning / Picket Fence | ±1 mm |
| Leaf transmission | Baseline consistency |
| Leaf speed | Within baseline |
SRS/SBRT Specialized QA
| Parameter | Tolerance / Requirement |
|---|---|
| Winston–Lutz Test | ≤1 mm |
| Radiation isocenter | ≤1 mm |
| Laser / ODI / Couch position | ±1 mm |
| Imaging coincidence / MLC positioning | ±1 mm |
| Output constancy | ±2% |
Imaging Systems QA
| Parameter | Tolerance / Requirement |
|---|---|
| kV imaging coincidence | ±2 mm |
| MV imaging coincidence | ±2 mm |
| CBCT coincidence | ±2 mm |
| Imaging vs treatment isocenter | ±2 mm |
Annual QA
| Parameter | Tolerance / Requirement |
|---|---|
| Absolute dose calibration | ±1% |
| Photon / Electron output | ±1% |
| Beam quality / Flatness / Symmetry | ±1% |
| Radiation isocenter | ≤2 mm diameter |
Electron Beam QA
| Parameter | Tolerance / Requirement |
|---|---|
| Output constancy / Symmetry | ±2% |
| Beam energy (R50/practical range) | ±2 mm |
| Flatness | ±3% |
| Applicator positioning | ±2 mm |
Safety Systems Interlocks
Door Interlock
Emergency OFF
Beam Interrupt
Collision Interlock
Audiovisual Mon.
Rad Monitor
R&V Comm.
MUST FUNCTION
