LINAC Tolerances Flashcards
Daily
X-ray output consistency (all energies)
3%
Daily
Laser localization - 3D
2mm
Daily
Laser localization - IMRT
1.5mm
Daily
Laser localization - SRS/SBRT
1mm
Daily
ODI at Iso - 3D
2mm
Daily
ODI at Iso - IMRT
2mm
Daily
ODI at Iso - SRS/SBRT
2mm
Daily
Collimator size - 3D
2mm
Daily
Collimator size - IMRT
2mm
Daily
Collimator size - SRS/SBRT
1mm
Daily
Door Interlock
Functional
Daily
Door closing safety
Functional
Daily
Audio/Visual
Functional
Daily
Radiation area monitor
Functional
Daily
Beam On indicator
Functional
Monthly
X-ray output
2%
Monthly
Typical dose rate output accuracy - IMRT and SRS/SBRT
2% at dose rate
Monthly
Photon bean profile constancy
1%
Monthly
Electron bean profile constancy
1%
Monthly
Electron bean energy constancy
2% / 2mm
Monthly
Light/radiation field
2mm or 1% on each side
Monthly
Light/radiation field - asymmetric
1mm or 1% on each side
Monthly
Gantry/collimator indicators
1 degree
Monthly
Accessory trays
2mm
Monthly
Jaw position indicators - symmetric
2mm
Monthly
Jaw position indicators - asymmetric
1mm
Monthly
Cross hair centering
1mm
Monthly
Tx couch positioning - 3D & IMRT
2mm / 1 degree
Monthly
Tx couch positioning - SRS/SBRT
1mm / 0.5 degree
Monthly
Wedge placement accuracy
2mm
Monthly
Compensator placement accuracy
1mm
Monthly
Latching of wedges & blocking tray
Functional
Monthly
Localization lasers - 3D
+- 2mm
Monthly
Localization lasers -IMRT
+- 1mm
Monthly
Localization lasers - SRS/SBRT
< +- 1mm
Monthly
Beam output constancy
2%
Monthly
Phase, amplitude beam control
Functional
Monthly
In-room respiratory monitoring system
Functional
Monthly
Gating Interlock
Functional
CT Simulator tolerances
Daily
CT Number accuracy
CT Number for water - 0 +- 5 HU
CT Simulator tolerances
Monthly:
CT Number accuracy
4 to 5 different materials - 0 +- 5HU
CT Simulator tolerances
Annually
CT Number accuracy
Electron density phantom - 0 +- 5 HU
Profile Tolerance
1% from Baseline
Calibration TG-51 Tolerance
1%
MLC Picket Fence Test Tolerance
Weekly
MLC Step/Shoot & Sliding Window
Annual
PDD/TMR Tolerance
1%
IGRT (KVCT and MVCT) iso check
Daily
IGRT (KVCT and MVCT) iso check tolerance
Daily:
2mm / 1mm (SRS)
Dynamic Wedge Output
Monthly
Profile Tolerance
1% from Baseline
Calibration TG-51 Tolerance
1%
MLC Picket Fence Test Tolerance
Weekly
MLC Step/Shoot & Sliding Window
Annual
PDD/TMR Tolerance
1%
IGRT (KVCT and MVCT) iso check
Daily
IGRT (KVCT and MVCT) iso check tolerance
2mm / 1mm (SRS)
Dynamic Wedge Output
Monthly
Annual:
Temporal accuracy of phase/amplitude gating
100ms of expected
Annual Calibration of surrogate for respiratory phase/amplitude
100ms of expected
Annual
Gating Interlock testing
Functional
Annual
X-ray flatness change from baseline
1%
Annual
X-ray symmetry change from baseline
+- 1%
Annual
Electron flatness change from baseline
1%
Annual:
Electron symmetry change from baseline
+- 1%
SRS arc rotation mode (range: .5-1.0 MU/deg)
MU set vs. delivered: 1MU or 2% (whichever is greater)
Gantry arc set vs. delivered: 1 degree or 2% (whichever is greater)
Annual
Calibration TG-51
1% Annual
Annual
Output Factors for Small Fields
< 2%
Annual
PDD/TMR
1%
Annual
TBI PDD X-ray
1%
Annual
TSET: electron PDD
1mm
Annual
TBI/TSET Output
2%
LINAC Wedge Tests
Daily: Functional
Monthly: Output
Annual: Profile
LINAC MLC Tests - Weekly
Picket Fence - visual inspection
LINAC MLC Tests - Monthly
Leaf Position Accuracy - 1mm for leaf positions of IMRT field for 4 cardinal gantry angles;
Travel speed - loss of leaf speed > 0.5 cm/s;
Leaf Setting vs Radiation Field - 2mm
LINAC MLC Tests - Weekly
Transmission - 0.5% from baseline;
Leaf Position Repeatability - +- 1mm;
MLC Spoke shot - < 1mm radius;
Rad-Light Coincidence - +-2mm;
Step & Shoot test - <0.35cm max error RMS, 95% of error counts<0.35 cm;
Moving Window test - <0.35cm max error RMS, 95% of error counts<0.35 cm
LINAC Annual Calibration - TG-51:
- Frequency - Annual
- Specified - In Water
- Calibration Factor - NDw
- Photons - Ion Chamber
- Photon Measurement depth - 10cm
6 .Photon Calibration depth - Dmax - Electrons - Parallel Plate Ion Chamber
- e’ Measurement depth - d reference
- e’ Calibration depth - Dmax
- Photon measurements use Pb foil - remove e’ contamination
How often are Ion chambers calibrated?
every 2 years