Table 4.

Difference in the mean between the pre‐calibration and post‐calibration data on three TrueBeam® machines (TB1, TB2, and TB3). Items in bold are statistically significant (P < 0.05).

Parameter	Head			Spotlight			Thorax			Pelvis
	TB1	TB2	TB3	TB1	TB2	TB3	TB1	TB2	TB3	TB1	TB2	TB3
Geometric distortion (mm)	−0.03	0.00	−0.01	0.00	0.00	0.00	0.07	−0.01	−0.05	0.02	−0.02	−0.05
Spatial resolution (lp/mm)	0.00	0.01	0.03	0.00	0.02	0.01	−0.04	0.00	0.00	−0.04	0.03	0.01
Uniformity (HU)	10.47	−30.73	−7.39	−12.95	−11.68	−14.04	−10.10	−12.16	0.98	−14.61	−17.26	6.83
Contrast (−)	−0.01	0.01	0.00	−0.01	0.00	0.00	−0.01	0.00	0.00	0.00	0.00	0.00
Noise (HU)	1.73	−2.02	−0.41	0.00	−0.03	−0.57	1.60	0.48	0.30	−0.40	0.24	−0.97
Air HU constancy (HU)	−3.20	2.24	−0.16	0.29	0.42	0.04	−0.47	0.51	0.09	−1.23	0.32	0.06
Teflon HU constancy (HU)	116.1	−31.72	2.90	8.10	−8.40	−5.05	42.62	−9.40	−0.33	14.19	−4.75	−12.93
Delrin HU constancy (HU)	50.62	−14.53	2.11	4.57	−4.53	−5.03	22.31	−3.31	4.43	7.84	−1.09	−4.38
Acrylic HU constancy (HU)	31.67	−9.06	1.91	2.88	−3.77	−6.16	17.63	−3.23	2.30	4.89	−0.45	−4.91
Polystyrene HU constancy (HU)	15.39	−5.32	0.04	1.66	−2.03	−4.66	10.14	−1.05	0.70	3.22	−0.35	−3.98
LDPE HU constancy (HU)	10.39	−3.47	−1.26	1.78	−2.91	−4.59	9.39	−1.65	3.73	3.04	−0.35	−3.89
PMP HU constancy (HU)	4.05	−3.98	−0.18	2.10	−1.32	−5.27	7.95	−1.50	6.17	2.45	1.02	0.91
20% bone HU constancy (HU)	39.82	−13.41	6.18	1.51	−6.45	−3.99	20.02	−4.55	6.55	7.44	−1.41	−3.77
50% bone HU constancy (HU)	93.39	−25.59	−11.08	2.22	−9.39	−15.70	34.12	−6.30	−7.60	10.07	−3.13	−23.39
Slice thickness (mm)	0.11	0.01	0.00	0.04	0.02	−0.08	−0.07	0.03	0.06	−0.01	−0.02	0.04