Role of metal artifact reduction software in computed tomography angiography of lower limb metallic prosthesis: A retrospective study

Table 1 Distribution of fixation device types

Fixation type	n	%
DHS	6	27.3
External fixation	3	13.6
Medullary nail	5	22.7
Plate and screws	6	27.3
Screws	1	4.5
THR	1	4.5

DHS: Dynamic hip screw; THR: Total hip replacement.

Table 2 Vascular pathology in study population

Pathology	n	%
Atherosclerosis	9	40.9
Normal	10	45.5
Tumor compression	3	13.6

Table 3 Location and laterality of prostheses

Parameter	n	%
Location
Femur	17	77.3
Tibia	5	22.7
Side
Right	11	50
Left	11	50

Table 4 Signal-to-noise ratio with and without metal artifact reduction, median (25^th percentile, 75^th percentile)

Observer	With MAR	Without MAR	Reference	P value
One	17.3 (8.5-30.2)	8.03 (1.99-26)	17.6 (6.65-42.5)	0.057
Two	12.98 (7.68-41.8)	5.74 (2.88-23.6)a	19.1 (8.2-36.5)	0.009
Three	16.5 (5.5-40.6)	6.5 (3.0-15.8)a	16.8 (7.1-43.0)	0.004

^aP < 0.05 signal-to-noise ratio without metal artifact reduction vs signal-to-noise ratio with metal artifact reduction.

Test of significance is Friedman’s test. MAR: Metal artifact reduction.

Table 5 Intraclass correlation coefficient for inter-observer agreement

Measurement	ICC	Absolute agreement	95%CI for ICC	P value
SNR
With MAR	0.751	Good	0.570-0.877	< 0.001
Without MAR	0.460	Poor	0.205-0.697	< 0.001
Reference	0.790	Good	0.628-0.898	< 0.001
CNR
With MAR	0.764	Good	0.488-0.809	< 0.001
Without MAR	0.487	Poor	0.230-0.717	< 0.001
Reference	0.810	Good	0.684-0.916	< 0.001

SNR: Signal-to-noise ratio; MAR: Metal artifact reduction; CNR: Contrast-to-noise ratio; ICC: Intraclass correlation coefficient; CI: Confidence interval.

Table 6 Overall artifact burden and image quality with vs without metal artifact reduction, median (minimum-maximum)

Characteristic	With MARS	Without MARS	MD1 (95%CI)	P value
Overall artifact	2 (2-5)	4 (3-5)	1.5 (1-2)	< 0.001
Overall image quality	1 (1-3)	2.5 (1-3)	1 (0.5-1)	< 0.001

¹MD = Hodges-Lehmann median difference.

Test of significance is Wilcoxon’s signed ranks test. MARS: Metal artifact reduction software; CI: Confidence interval.

Table 7 Inter-observer agreement of subjective assessment

Image type	Study quality assessment (W)	Study quality (P value)	Artifact assessment (W)	P value
MAR-reconstructed	0.899	< 0.001	0.918	< 0.001
Non-MAR	0.847	< 0.001	0.922	< 0.001

Kendall’s Coefficient of Concordance (W). MAR: Metal artifact reduction.