Evaluation of Metal Artifacts from Stainless Steel and Titanium Alloy Orthopedic Screw in Computed Tomography Imaging

Abstract

Artifacts arising from metallic implant had been a concern for Computed Tomography (CT) imaging in obtaining optimal image quality. The main aim of this study was to evaluate the metal artifacts severity from two different types of orthopedics screw and to optimise CT imaging parameters for metallic implants. A water-based abdomen phantom of diameter 32 cm (adult body size) was fabricated using polymethyl methacrylate (PMMA) materials. The fabricated phantom was scanned with dual-energy CT at 80 and 140 kV, and single-energy CT at 120 kV. Two types of orthopedic screws; titanium alloy (grade 5) and stainless steel (grade 316L) was used in this study. A phantom with orthopedics metal screw was scanned at various pitch (0.35, 0.60, 1.20) and slice thickness of 1.0, 3.0, 5.0 mm. The tube current was applied automatically using tube current modulation. In this phantom study, the severity of stainless steel and titanium alloy was analysed. Results showed that the signal-to-noise ratio (SNR) of titanium alloy was higher than the SNR of stainless steel. The optimal image quality of metallic implant was obtained at imaging parameters of pitch at 0.60 and 5.0 mm slice thickness. The use of optimum CT imaging parameters for orthopedic screw resulted in an improved CT image, as the SNR increases. This finding proves that optimum CT imaging parameters are able to reduce the metal artifacts severity on CT images. Therefore, it has potential for improving diagnostic performance in patients with severe metallic artifacts.