ABSTRACT
Abstract@#Introduction: Computed tomography (CT) has been widely used for postoperative spine assessment. However, the effectiveness of CT is limited by the presence of multiple artefacts surrounding metal implants. An artefact causes degradation of image quality and obscures the interpretation of spine CT images by a radiologist. The purpose of this study was to evaluate the optimum angle of gantry tilt and metal rod placement which produced the least metal artefact on CT images. Methods: A customised phantom was developed with different transverse angles of metal placement. The transverse angles of metal placement inside the phantom varied at 20°, 30°, 40° and 45°. The phantom was scanned with CT scanner at 0° axial scan angle. It was followed by acquisitions at different gantry tilt angles ranging from −12° to 20°. Quantitative and qualitative assessment by determining the signal-to-noise ratios (SNRs) of the CT images was performed. Results: The severity of the metal streak artefact increased as the metal insertion angles became wider up to 45° due to the widespread of streaking area. The severity of artefacts was reduced with the increment of the gantry tilt angle, which was observed in images acquired at 20°. Conclusion: For the gantry tilt angulation technique, the optimum gantry angle for metal artefact reduction is at the widest angle, which is +20° angulation. Although the gantry tilt technique did not eliminate the metal artefacts, it enabled a significant reduction of metal artefacts and improved image quality.