Table 2.

Median and ranges of differences between the original pCT and the CBCT DVHs for primary (PTV74) and nodal (PTV60) planning target volumes, together with rectum and bladder as OARs (prostate patients)

Target & OAR	Constraint	Standard pCT calibration curve	CBCT site-specific calibration curve	HU density over ride	Deformable registration
		Median difference (min;max)	Median difference (min;max)	Median difference (min;max)	Median difference (min;max)
PTV74	Dose to 99%	0.0	–0.2	0.3	0.1
	of the volume [%]	( _0.3; 1.1)	(–0.7; 0.7)	(0.2; 0.4)	(–-0.4; 0.9)
	Dose to 98%	0.1	–0.5	0.4	0.2
	of the volume [%]	(–0.3; 1.1)	(0.7; 0.6)	(0.0; 0.4)	(–0.4; 0.7)
	Max dose to 1%	0.6	0.2	0.6	0.1
	of the volume [%]	(0.0; 1.4)	(–0.5; 1.0)	(0.4; 0.8)	(–0.4; 0.9)
PTV60	Dose to 99%	–0.3	–0.3	–0.2	0.2
	of the volume [%]	(–1.1; 0.3)	(–1.4; 0.3)	(0.4; 0.7)	(–0.6; 0.6)
	Dose to 98%	0.2	–0.2	0.0	0.1
	of the volume [%]	(–0.9; 0.5)	(–1.2; 0.1)	(–0.4; 0.8)	(–0.4; 1.0)
	Max dose to 1%	0.2	–0.3	0.0	0.0
	of the volume [%]	(–0.5; 1.3)	(–0.8; 0.7)	(–0.3; 0.5)	(–0.5; 1.0)
Rectum	Dose to 60%	0.4	-0.1	0.1	0.1
	of the volume [Gy]	(0.0; 1.5)	(-0.7; 0.4)	(-–0.1; 1.1)	(–0.5; 0.7)
	Dose to 15%	1.0	0.3	0.4	0.2
	of the volume [Gy]	(0.1; 1.8)	(–-0.3; 1.0)	(0.3; 1.0)	(–0.3; 1.2)
Bladder	Dose to 50%	0.0	0.0	0.1	0.0
	of the volume [Gy]	(–0.2; 0.6)	(–0.3; 0.5)	(–0.2; 0.3)	(–0.2; 0.6)
	Dose to 35%	0.1	0.0	0.2	0.1
	of the volume [Gy]	(–0.2; 0.6)	(–0.4; 0.4)	(–0.2; 0.3)	(–0.3; 0.6)

CBCT, cone beam CT; DVH, dose volume histogram; HU, Hounsfield unit; OAR, organ at risk; PTV, planning target volume.