Optimizing imaging techniques in the postoperative patient.

Postoperative patients may develop complications requiring imaging. Although any imaging technique can be used to investigate these patients, the presence of metal hardware in the region of interest may distort the image and interfere with diagnosis. It is important to understand why this distortion occurs and how to compensate for it. Because some of the most common cross-sectional imaging methods used to image this patient population are computed tomography (CT) and magnetic resonance imaging (MRI), this article focuses on these imaging methods. Metal-related artifacts on CT depend on the hardware alloy, the geometry of the hardware, and the location of the hardware relative to the region of interest. The artifacts may be reduced or eliminated by altering the scan technique, changing the patient position, selecting a smoother CT reconstruction algorithm, and by creating thicker slice multiplanar reformations. Like CT, metal artifacts at MR imaging depend on the type of hardware alloy. Hardware-related artifacts at MR imaging can be reduced by using appropriate pulse sequences, such as fast or turbo spin echo and inversion recovery. Additionally, important pulse sequence modifications that are addressed here include manipulation of the receiver bandwidth and orientation of the frequency encode axis.