Table 2.

The dice similarity coefficient (DSC) values between 4D cone-beam computed tomography (CBCT) ventilation images from different methods and clinical standard SPECT ventilation image for different functional lung regions and the statistical differences for these different methods.

	DSC				P-value
	High functional lung (HFL) region	Medium functional lung (MFL) region	Low functional lung (LFL) region	Average	HFL	MFL	LFL	Average
CBCT-VI derived methods
HU	0.34 ± 0.04	0.34 ± 0.02	0.34 ± 0.06	0.34 ± 0.04
JAC	0.34 ± 0.04	0.34 ± 0.03	0.34 ± 0.04	0.34 ± 0.03
DL (1)	0.60 ± 0.10	0.47 ± 0.07	0.70 ± 0.07	0.59 ± 0.08
DL (2)	0.59 ± 0.10	0.46 ± 0.08	0.70 ± 0.08	0.58 ± 0.09
Comparison for the different methods
HU and DL (1)/HU and DL (2)					<10−8/10−8	<10−8/10−8	<10−8/10−8	<10−8/10−8
JAC and DL (1)/JAC and DL (2)					<10−8/10−8	<10−8/10−8	<10−8/10−8	<10−8/10−8
HU and JAC					0.9999	0.9868	1.0000	1.0000
DL (1) and DL (2)					0.9964	0.9916	0.9971	0.9953