Table 7.

Monthly routine QA for EPID-based QA systems

2D PTQA
Test	Technique	Metric	Tolerance
Dose constancy	10 × 10cm static field	% Dose difference*	±2%
2D static field	25 × 25cm static field	2D γ	Baseline ± 2%†
Patient/test plan	IMRT	2D γ	Baseline ± 2%†
Patient/test plan	VMAT	2D γ	Baseline ± 2%†
Positioning	25 × 25cm static field	Distance	±2 mm (non-SBRT/SRS)
	@ Cardinal angles		±1 mm (SBRT/SRS)
Scaling	25 × 25cm static field	Distance	±2 mm
2D Transit Dosimetry QA
Test	Technique	Comparison Method	Tolerance
Dose constancy	25 × 25cm	% Dose difference	±2%
2D static field	25 × 25cm	2D γ	Baseline ± 3%†
Patient/test plan	IMRT	2D γ	Baseline ± 3%†
Patient/test plan	VMAT	2D γ	Baseline ± 3%†

^*Mean dose of small area around the central axis no larger than 1 × 1 cm.

^†Baseline pass rates should be established during EPID QA system commissioning and deviations in the pass rate in either direction should be monitored. For example, if an institution’s baseline was 95% pass rate at (3%/2 mm), the tolerance limits should be 93–97% with ±2% tolerance and 92–98% with ±3% tolerance using the same criteria.