CT-Guided Intervention: Reduction of Metal Artifact Using an Off-Axis Reconstruction Method

OBJECTIVE: Needle artifact redistribution technique (Needle-ART) is a recently developed image artifact-reduction method for CT-guided needle procedures. The principle of this technique is to create an angle between the needle and imaging plane by tilting the CT gantry, then reformatting images along the needle plane, thus redistributing the artifact out of the viewing plane. The purpose of this study is to evaluate the feasibility, artifact reduction, and clinical applicability of Needle-ART for the placement of biopsy introducer needles into the liver, kidneys, and lungs of a deceased animal model. METHODS: A paired before-and-after study was performed in 2 deceased swine to evaluate the effectiveness of Needle-ART in reducing metal artifacts during CT-guided interventions. A 17G co-axial needle was inserted into the liver, kidney, and lung at 6 sites per organ and scanned at each site with both 0-degree gantry tilt (standard axial as the control group) and 6-degree tilted gantry on Needle-ART. A total of 48 scans with 24 control and 24 Needle-ART were collected. Images were reformatted to align with the needle trajectory. Collected images were evaluated for overall artifact severity by 3 blinded radiologists. RESULTS: Needle-ART significantly reduced metal artifacts across all quantitative metrics, which was consistent with blinded reader assessments. Mean artifact length was reduced by 35.5% (P=0.0019) in liver, 65.9% (P=0.003) in kidney, and 59.4% (P=0.0021) in lung. Median artifact width decreased by 30% (P=0.028) in liver, 24.3% (P=0.028) in kidney, and 8.3% (P=0.017) in lung. Median artifact intensity was reduced by 38.8% (P=0.011) in liver, 35.4% (P=0.028) in kidney, and 23.6% (P=0.021) in lung. The radiologists scored conventional CT images (with non-tilted gantry) significantly worse artifacts compared with Needle-ART (with tilted gantry) (P=0.000041). CONCLUSIONS: The off-axis reconstruction method is a novel technique that effectively reduces artifacts by acquiring scans with the CT gantry tilted 6 degrees relative to the plane containing the needle and target.