Managing postoperative artifacts on computed tomography and magnetic resonance imaging.

Orthopedic hardware should not be considered a contraindication to computed tomography (CT) or magnetic resonance (MR) imaging. The hardware alloy, the geometry of the hardware, and the orientation of the hardware all affect the magnitude of image artifacts. For commonly encountered alloys, the severity of image artifacts is similar for CT and MR. Cobalt chrome or stainless steel hardware produces the most artifacts; titanium hardware produces the least. In general, image artifacts are most severe adjacent to the hardware. CT image artifacts are related to incomplete X-ray projection data resulting in streaks. These can be mitigated by increasing scan technique and using a smoother reconstruction filter. Hardware with a rectangular cross-sectional shape such as a fixation plate will cause more artifacts than a radially symmetrical device such as an intramedullary nail. Image artifacts at MR are caused by the hardware magnetic susceptibility and the induction of eddy currents within the metal. A turbo spin-echo sequence yields the best results. The use of larger image matrices, thinner slices, and a wide receiver bandwidth are recommended parameter adjustments when imaging patients with hardware. This article discusses how hardware-related artifacts can be minimized by altering scan technique and image reconstruction.