Table 3.

Tests performed to characterize kV‐IGRT system and suggested tolerances

Detailed tests		Test results	Suggested tolerances
Mechanical accuracy	Laser localization	<1 mm	1 mm
	kV imager projection offset	<0.2 mm	0.5 mm
	kV field edge accuracy	<1.7 mm	2 mm
Geometric accuracy	Imaging and treatment coordinate coincidence	<1 mm	2 mm
Patient setup accuracy	kV 3D–3D match	<0.5 mm	1 mm
Image quality tests (regular and iCBCT reconstructions on all protocols)	Spatial resolution	C: ≥5 lp/cm	C: not worse than 5 lp/cm
		Q: per protocol (0.25–0.68 cycles/mm)	Q: per protocol
	Low‐contrast resolution	C: all HU inserts are visible	C: all HU inserts are visible
		Q: per protocol (2–20 for regular CBCT)	Q: >2
	CT number uniformity	C: ±30 HU	±40 HU
		Q: ±30 HU
	CT number consistency	C: ±50 HU	±50 HU
		Q: ±50 HU
	Slice thickness	C: <0.5 mm	0.5 mm
		Q: <0.5 mm
	Spatial linearity	<1 mm	1 mm
Dosimetry	kV CBCT dose accuracy	<20 mGy within specs	Per protocol (1–40 mGy)
	kV CBCT dose consistency	<20 mGy within baseline	Per protocol (1–40 mGy)

In the table, C represents the measurements with the Catphan phantom, and Q represents the measurement with the QUART phantom.