Table 3.

Global parenchymal results. Difference measures comparing parenchymal values between control and target protocols and between the two target protocols acquired for the mean, median, standard deviation, and percent emphysema (% < −910 HU). Values were not reported for the second target volume for the control variability set indicated with an n/a

	Mean (HU)			Median (HU)			Standard deviation (HU)			% < −910 HU (%)
Average across all control protocols	−814.25 ± 10.38			−836.6 ± 7.47			86.47 ± 9.31			0.40 ± 0.09
Protocol	X1–Xc	X2–Xc	X2–X1	X1–Xc	X2–Xc	X2–X1	X1–Xc	X2–Xc	X2–X1	X1–Xc	X2–Xc	X2–X1
Control variability	−1.06	n/a	n/a	0.00	n/a	n/a	−1.49	n/a	n/a	0.11	n/a	n/a
No‐TCM	−2.60	−4.96	2.37	−2.00	−5.00	3.00	−0.24	−1.46	1.22	0.11	0.21	−0.10
Low‐dose	−2.00	−6.64	4.63	−1.00	−5.00	4.00	−0.03	−1.92	1.89	0.90	1.26	−0.36
Ultralow‐dose	0.68	−1.14	1.82	3.00	1.00	2.00	1.08	0.65	0.43	2.07	2.29	−0.22
Tin‐filtered ultralow‐dose	1.90	0.19	1.71	5.00	2.00	3.00	2.91	4.21	−1.31	2.97	3.03	−0.06