Table 3.

Average execution time for each proposed level with the respected image size

No	Level (image size)	Average execution time (s)
1	Contrast adjustment block (original size)	0.68
2	Cropping block (original size)	0.15
3	Get spine axis (512 by 512 to get the spine, then reduced 256 by 256 when using HT)	0.29
4	Segmentation using GD, thresholding and FCM	13.71
	- Estimate lung outline (GD) (512 by 512)	(9.79)
	- Fill the lung outline (thresholding) (256 by 256)	(0.96)
	- Refine lung region (FCM) (256 by 256)	(2.96)