Table 3.

The “trachea” like region of a variant of the COPDGene phantom was scanned in SS mode (80, 100, 120 and 140 kVp), in the DSDE mode (80/140Sn kVp, 140/80 kVp, and 100/140Sn kVp), and in the DSDE-SS mode (the same combinations as in the DSDE mode but with tube A or B set at min mAs). A consistent CTDIvol of 12 (+/− 0.1) mGy was used for each. The results here show the mean HU for a sampling of the analyzed parameter changes. Additional controlled scans comparing slice thickness (0.6 or 0.75mm), slice spacing (0.5 or 0.6mm), and scan direction (cranio-caudal or caudo-cranial) were also analyzed but not shown to have any meaningful difference in mean values compared to the control.

Phantom “Trachea” values
	Scan Mode	Mean	Channels	Pitch	Rot. Time	Kernel	Tube	Sn filtered
80 kVp	SS	−987	128	0.55	0.5	B35f	A	-
	DSDE-SS	−1002	64	0.55	0.5	B35f	A	-
	DSDE-SS	−1002	128	0.55	0.5	B35f	A	-
	DSDE	−1002	128	0.55	0.5	B35f	A	-
	DSDE	−1002	128	1.0	0.5	B35f	A	-
	DSDE	−1001	128	0.55	0.33	B35f	A	-
	DSDE	−1003	128	0.55	0.5	D30f	A	-
	DSDE-SS	−1003	64	0.55	0.5	B35f	B	-
	DSDE-SS	−1004	128	0.55	0.5	B35f	B	-
	DSDE	−1003	128	0.55	0.5	B35f	B	-
	DSDE	−1002	128	1.0	0.5	B35f	B	-
	DSDE	−1003	128	0.55	0.33	B35f	B	-
	DSDE	−1002	128	0.55	0.5	D30f	B	-
100 kVp	SS	−988	128	0.55	0.5	B35f	A	-
	DSDE-SS	−1004	64	0.55	0.5	B35f	A	-
	DSDE-SS	−1007	128	0.55	0.5	B35f	A	-
	DSDE	−1002	128	0.55	0.5	B35f	A	-
120 kVp	SS	−985	128	0.55	0.5	B35f	A	-
140 kVp	SS	−987	128	0.55	0.5	B35f	A	-
	DSDE-SS	−1002	64	0.55	0.5	B35f	A	-
	DSDE-SS	−1007	128	0.55	0.5	B35f	A	-
	DSDE	−1002	128	0.55	0.5	B35f	A	-
	DSDE-SS	−1000	64	0.55	0.5	B35f	B	yes
	DSDE-SS	−1001	128	0.55	0.5	B35f	B	yes
	DSDE	−1003	128	0.55	0.5	B35f	B	yes

Note: Reference CT number for internal “trachea” air is −1000 HU.