TG-142 Values Flashcards
Daily tolerance for laser localization, SRS/SBRT
1 mm
Daily tolerance for laser localization, IMRT
1.5 mm
Daily tolerance for ODI @ iso
2 mm
Daily tolerance for output
3%
Monthly tolerance for output constancy
2%
Monthly photon and electron beam profile constancy
1%
Monthly front pointer test tolerance
1 mm for 100 SSD
Monthly Gantry/collimator angle indicators vs digital level tolerance
1 degree
Monthly light/radiation field coincidence tolerance for symmetric and assymetric
Symmetric: 2 mm, or 1% on a side
Asymmetric: 1 mm or 1% on a side
Monthly Treatment couch LNG, VRT and LAT position indicators tolerance for SBRT/SRS and IMRT
IMRT: 2 mm
SBRT/SRS: 1 mm
Treatment couch position indicators pitch, roll and rotation, for SBRT/SRS and IMRT
IMRT: 1 degree
SBRT/SRS: 0.5 degree
Monthly CBCT geometric distortion
<= 1 mm
Monthly HU constancy tolerance
Baseline +- 50 HU
Monthly kV and MV scaling tolerance
MV: <= 2 mm
kV: <= 1 mm (SRS/SBRT)
Monthly pattern test tolerance
2 mm
Weekly picket fence tolerance
Visual inspection. Clinic chooses tolerance
Monthly picket fence tolerance
1 mm
Annual flatness and symmetry tolerance
1%
Monthly and annual roll-out test tolerance
1 mm
Annual temporal accuracy of phase/amplitude gate on and off
100 ms of expectation
Daily collimator size indicator tolerance
1 mm SRS/SBRT
2 mm IMRT
Annual x-ray output constancy vs dose rate
+- 2%
Annual x-ray output calibration tolerance
+- 1%
Annual photon beam quality tolerance
1% PDD10
Annual electron beam quality tolerance
+-1 mm R50
Annual physics wedge transmission factor constancy
+- 2%
Describe action level 1
Inspection action
Sudden and significant deviation from expected values that have become normal in your mind from QAing frequently
Values may still be within tolerance, but they should deem inspection if sudden jump
Actions: treatment may continue, but the cause should be investigated
Ex. WL max deltas of 0.8 - 0.9. It’s still within tolerance, but it’s just suspicious. Probably setup error
Describe action level 2
Scheduled action
Results of QA procedure that are at or near tolerance
Should cause investigation or scheduled maintence
If a single result exceeds tolerance value, but not by much, you should investigate or schedule maintence
Action: schedule time to correct within next week, but treatment may continue since clinical impact in short amount of time shouldn’t be major
Describe action level 3
Immediate action or stop treatment or correction action
Malfunctions or excessive errors that are too significant
You need to stop treatment until it gets fixed
Ex. nonfunctional safety interlocks
Ex. Excessive error in dosimetric quantity (like output)
What is the average leaf speed, and what is tolerance for a TG-142 month QA?
Typical average is 2.5 cm/s
Tolerance is - 0.5 cm/s
