Ablation margin assessment of liver tumors with intravenous contrast-enhanced C-arm computed tomography

Table 1 Patient size, computed tomography numbers and quantitative image noise at different magnitude and direction of off-centering (mean±SD)

Distance (#patients)	Direction (#patients)	BMI (kg)	Weight (mGy)	AP diameter (cm)	CTDIvol	aHU	pHU	LivHU	aSD	pSD	LivSD
0-5 mm (n = 75)	Ideal centering	27 (18-59)	77 (31-181)	28 (17-52)	13.4 (5.2-48.3)	-97.5 ± 27.2 (-117~-45)	-92.8 ± 14.9 (-121~-34)	117.0 ± 43.4 (63~153)	9.9 ± 4.9 (5~45)	11.8 ± 4.3 (4~33)	17.0 ± 3.7 (9~15)
6-10 mm (n = 47)	A (n = 20)	28 (20-38)	76 (54-107)	27 (17-33)	14.1 (9.0-33.0)	-98.2 ± 9.3 (-115~-78)	-90.9 ± 9.5 (-106~ -71)	114.0 ± 20.0 (55~153)	11.0 ± 2.6 (6~18)	12.3 ± 3.0 (7~16)	17.8 ± 3.4 (10~30)
	B (n = 27)	28 (21-40)	79 (54-127)	29 (20-53)	13 (7.2-23.4)	-95.1 ± 13.1 (-115~-60)	-88.7 ± 19.3 (-109~-59)	117.6 ± 26.9 (80~167)	9.7 ± 2.3 (6~15)	13.4 ± 4.01 (8~23)	17.4 ± 5.2 (13~23)
11-20 mm (n = 125)	A (n = 47)	30 (19-51)	88 (54-130)	31 (23-40)	15.4 (9.2-42.2)	-96.9 ± 13.4 (-116~-45)	-93.3 ± 14.0 (-114~-44)	109.9 ± 22.5 (63~158)	11.0 ± 3.6 (5~22)	12.6 ± 3.7 (7~23)	18.1 ± 4.9 (11~31)
	B (n = 78)	27 (17-49)	74 (35-136)	28 (15-44)	13.2 (5.8-34.5)	-97.1 ± 13.1 (-115~-53)	-92.9 ± 11.8 (-124~63)	119.3 ± 25.2 (31~175)	9.5 ± 2.4 (6~18)	11.9 ± 3.2 (8~21)	17.9 ± 4.3 (11~29)
21-30 mm (n = 85)	A (n = 22)	29 (20-37)	89 (46-129)	32 (19-53)	13.9 (6.2-26.7)	-96.5 ± 10.9 (-112~-74)	-89.0 ± 12.8 (-118~-56)	107.4 ± 26.31 (40~142)	12.4 ± 3.31 (7~20)	13.6 ± 3.91 (9~24)	18.7 ± 3.81 (6~20)
	B (n = 63)	26 (15-35)	73 (40-109)	27 (17-38)	12.7 (5.9-23.5)	-94.6 ± 13.7 (-113~-44)	-85.3 ± 13.01 (-110~-43)	122.3 ± 25.1 (55~177)	10.4 ± 2.8 (6~23)	13.3 ± 3.71 (6~22)	17.9 ± 4.9 (11~34)
³31 mm (n = 63)	A (n = 10)	36 (22-52)	96 (65-141)	34 (28-46)	14.2 (10.1-21.1)	-94.3 ± 7.4 (-103~-80)	-89.1 ± 16.6 (-100~-77)	116.6 ± 24.8 (81~153)	16.4 ± 7.01 (9~29)	14.0 ± 5.0 (8~24)	26.7 ± 4.01 (21~38)
	B (n = 53)	26 (19-38)	74 (49-118)	27 (19-36)	14.1 (6.1-42.6)	-94.1 ± 13.7 (-129~-68)	-87.1 ± 13.5a (-113~-61)	125.0 ± 24.8a (63~167)	9.4 ± 2.5 (6~18)	13.5 ± 4.7a (8~30)	17.2 ± 4.0 (11~30)

^aImplies significant statistical difference (P < 0.05). Off-centering distance and direction had a greater effect on image noise as compared to the mean computed tomography (CT) numbers. Numbers in parentheses are ranges. A: Superior off-centering; B: Inferior off-centering; aHU: Mean CT numbers in the anterior abdominal wall; pHU: Mean CT numbers in the posterior abdominal wall; LivHU: Mean CT numbers in liver, aSD: Quantitative noise in the anterior abdominal wall; pSD: Quantitative noise in the posterior abdominal wall; LivSD: Quantitative noise in the liver.