Assessment of sub-milli-sievert abdominal computed tomography with iterative reconstruction techniques of different vendors

Table 1 Mean age, weight, body mass index, and effective diameter for vendor A, B and C

	Vendor A	Vendor B	Vendor C
Age (yr)	60 ± 13	63 ± 12	58 ± 13
weight (kg)	84 ± 18	75 ± 16	89 ± 24
BMI (kg/m2)	28 ± 5	27 ± 5	30 ± 8
Effective diameter (cm)	31 ± 4	30 ± 4	31 ± 5

BMI: Body mass index.

Table 2 Mean computed tomography dose index volume, dose length product, and estimated effective dose for standard of care and reduced dose computed tomography for vendor A, B and C

	Vendor A		Vendor B		Vendor C		P value
	SD	RD	SD	RD	SD	RD
CTDIvol (mGy)	10 ± 3.4	1.2 ± 0.1	10 ± 3.4	1.3 ± 0.1	9 ± 5.3	1.4 ± 0.1	< 0.001
DLP (mGy*cm)	483 ± 187	64 ± 2	426 ± 204	61 ± 3	386 ± 259	61 ± 3	< 0.001
Estimated effective dose (mSv)	7 ± 3	0.9 ± 0.1	6 ± 3	0.9 ± 0.1	6 ± 4	0.9 ± 0.1	< 0.001

DLP: Dose length product; CTDI_vol: Computed tomography dose index volume; SD: Standard of care; RD: Reduced dose.

Table 3 Subjective image quality scores for reduced dose A-1, reduced dose A-2, and reduced dose A-3

	A-1		A-2		A-3
Reader 1
Lesions	1 (7/24)	2 (16/24)	1 (10/24)	2 (13/24)	1 (7/24)	2 (15/24)
	3 (1/24)		3 (1/24)		3 (2/24)
Liver margins	1 (18/22)	2 (4/22)	1 (20/22)	2 (2/22)	1 (17/22)	2 (5/22)
Liver parenchyma	1 (4/22)	2 (15/22)	1 (7/22)	2 (14/22)	1 (5/22)	2 (15/22)
	3 (3/22)		3 (1/22)		3 (2/22)
Adrenals bowels	1 (7/22)	2 (15/22)	1 (11/22)	2 (11/22)	1 (8/22)	2 (14/22)
	1 (7/22)	2 (14/22)	1 (10/22)	2 (12/22)	1 (8/22)	2 (14/22)
	3 (1/23)
Reader 2
Lesions	1 (5/25)	2 (17/25)	1 (8/25)	2 (12/25)	1 (7/25)	2 (13/25)
	3 (3/25)		3 (5/25)		3 (5/25)
Liver margins	1 (10/22)	2 (11/22)	1 (12/22)	2 (10/22)	1 (9/22)	2 (13/22)
	3 (1/22)
Liver parenchyma	1 (2/22)	2 (8/22)	1 (2/22)	2 (10/22)	1 (2/22)	2 (10/22)
	3 (12/22)		3 (10/22)		3 (10/22)
Adrenals	1 (7/22)	2 (12/22)	1 (9/22)	2 (11/22)	1 (7/22)	2 (13/22)
	3 (3/22)		3 (2/22)		3 (2/22)
Bowels	1 (12/22)	2 (8/22)	1 (12/22)	2 (8/22)	1 (10/22)	2 (10/22)
	3 (3/22)		3 (2/22)		3(2/22)

Score (seen by number of lesions or patients/total number of lesions or patients), score of 1 = sufficient, 2 = limited, 3 = unacceptable for clinical diagnostic confidence.

Table 4 Subjective image quality scores for reduced dose B-1, reduced dose B-2, and reduced dose B-3

	B-1		B-2		B-3
Reader 1
Lesions	1 (4/27)	2 (22/27)	1 (4/27)	2 (19/27)	1 (7/27)	2 (18/27)
	3 (1/27)		3 (4/27)		3 (2/27)
Liver margins	1 (14/22)	2 (8/22)	1 (12/22)	2 (10/22)	1 (16/22)	2 (6/22)
Liver parenchyma	1 (1/22)	2 (16/22)	1 (1/22)	2 (14/22)	1 (1/22)	2 (16/22)
	3 (5/22)		3 (7/22)		3 (5/22)
Adrenals	1 (2/22)	2 (14/22)	1 (2/22)	2 (13/22)	1 (3/22)	2 (15/22)
	3 (6/22)		3 (7/22)		3 (4/22)
Bowels	3 (7/23)	2 (15/22)	3 (7/23)	2 (15/22)	3 (6/23)	2 (16/22)
Reader 2
Lesions	1 (5/30)	2 (19/30)	1 (8/30)	2 (18/28)	1 (7/30)	2 (15/30)
	3 (6/30)		3 (4/30)		3 (8/30)
Liver margins	1 (6/22)	2 (14/22)	1 (8/22)	2 (13/22)	1 (6/22)	2 (14/22)
	3 (2/22)		3 (1/22)		3 (2/22)
Liver parenchyma	3 (17/22)	2 (5/22)	3 (16/22)	2 (6/22)	3 (18/22)	2 (4/22)
Adrenals	1 (3/22)	2 (10/22)	1 (4/22)	2 (11/22)	1 (2/22)	2 (9/22)
	3 (9/22)		3 (7/22)		3 (11/22)
	3 (4/22)		3 (1/22)		3 (5/22)
Bowels	1 (4/22)	2 (16/22)	1 (5/22)	2 (16/22)	1 (3/22)	2 (17/22)
	3 (2/22)		3 (1/22)		3 (2/22)

Score (seen by number of lesions or patients/total number of lesions or patients), score of 1 = sufficient, 2 = limited, 3 = unacceptable for clinical diagnostic confidence.

Table 5 Subjective image quality scores for reduced dose C-1, reduced dose C-2, and reduced dose C-3

	C-1		C-2		C-3
Reader 1
Lesions	1 (2/19)	2 (11/19)	1 (5/19)	2 (10/19)	1 (7/19)	2 (9/19)
	3 (6/19)		3 (4/19)		3 (3/19)
Liver margins	1 (8/22)	2 (14/22)	1 (13/22)	2 (9/22)	1 (16/22)	2 (6/22)
Liver parenchyma	1 (1/22)	2 (13/22)	1 (2/22)	2 (14/22)	1 (2/22)	2 (17/22)
	3 (8/22)		3 (6/22)		3 (3/22)
Adrenals	1 (4/22)	2 (13/22)	1 (5/22)	2 (14/22)	1 (7/22)	2 (12/22)
	3 (5/22)		3 (3/22)		3 (3/22)
Bowels	1 (4/22)	2 (14/22)	1 (4/22)	2 (13/22)	1 (5/22)	2 (14/22)
	3 (4/23)		3 (5/23)		3 (3/23)
Reader 2
Lesions	1 (6/20)	2 (9/20)	1 (7/20)	2 (10/20)	1 (13/20)	2 (6/20)
	3 (5/20)		3 (3/20)		3 (1/20)
Liver margins	1 (6/22)	2 (12/22)	1 (7/22)	2 (11/22)	1 (9/22)	2 (11/22)
	3 (4/22)		3 (4/22)		3 (2/22)
Liver parenchyma	1 (2/22)	2 (5/22)	1 (3/22)	2 (6/22)	1 (4/22)	2 (5/22)
	3 (15/22)		3 (13/22)		3 (13/22)
Adrenals	1 (5/22)	2 (8/22)	1 (6/22)	2 (7/22)	1 (9/22)	2 (6/22)
	3 (10/22)		3 (9/22)		3 (7/22)
Bowels	1 (10/22)	2 (10/22)	1 (12/22)	2 (8/22)	1 (13/22)	2 (8/22)
	3 (2/22)		3 (2/22)		3 (1/22)

Score (seen by number of lesions or patients/total number of lesions or patients) score of 1 = sufficient, 2 = limited, 3 = unacceptable for clinical diagnostic confidence.

Table 6 Mean HU values and objective image noise in region of interest placed in liver for standard of care filtered back projection and reduced dose iterative reconstruction techniques

		HU values	Objective image noise
Vendor A	SD FBP	104 ± 30	17 ± 3
	RD A-1	93 ± 35	16 ± 4
	RD A-2	97 ± 29	19 ± 4
	RD A-3	98 ± 29 (P = 0.9)	24 ± 5 (P < 0.001)
Vendor B	SD FBP	101 ± 28	26 ± 5
	RD B-1	100 ± 25	29 ± 5
	RD B-2	98 ± 24	14 ± 3
	RD B-3	107 ± 23 (P = 0.3)	33 ± 11 (P < 0.001)
Vendor C	SD FBP	103 ± 28	23 ± 7
	RD C-1	97 ± 26	36 ± 18
	RD C-2	97 ± 26	28 ± 14
	RD C-3	98 ± 25 (P = 0.9)	23 ± 11 (P = 0.016)

FBP: Filtered back projection; SD: Standard of care; RD: Reduced dose.