Overcoming artifacts from metallic orthopedic implants at high-field-strength MR imaging and multidetector CT

At magnetic resonance ( MR) imaging and multidetector computed tomography ( CT), artifacts arising from metallic orthopedic hardware are an obstacle to obtaining optimal images. Although various techniques for reducing such artifacts have been developed and corroborated by previous researchers, a new era of more powerful MR imaging and multidetector CT modalities has renewed the importance of a systematic consideration of methods for artifact reduction. Knowledge of the factors that contribute to artifacts, of related theories, and of artifact reduction techniques has become mandatory for radiologists. Factors that affect artifacts on MR images include the composition of the metallic hardware, the orientation of the hardware in relation to the direction of the main magnetic field, the strength of the magnetic field, the pulse sequence type, and other MR imaging parameters ( mainly voxel size, which is determined by the field of view, image matrix, section thickness, and echo train length). At multidetector CT, the factors that affect artifacts include the composition of the hardware, orientation of the hardware, acquisition parameters ( peak voltage, tube charge, collimation, and acquired section thickness), and reconstruction parameters ( reconstructed section thickness, reconstruction algorithm used, and whether an extended CT scale was used). A comparison of images obtained with different hardware and different acquisition and reconstruction parameters facilitates an understanding of methods for reducing or overcoming artifacts related to metallic implants. (C) RSNA, 2007.