Three-dimensional quantification of susceptibility artifacts from various metals in magnetic resonance images

Susceptibility artifacts generated in magnetic resonance (MR) images were quantitatively evaluated for various metals using a three-dimensional (3-D) artifact rendering to demonstrate the correlation between magnetic susceptibility and artifact volume. Ten metals (stainless steel, Co-Cr alloy, Nb, Ti, Zr, Mo, Al, Sn, Cu and Ag) were prepared, and their magnetic susceptibilities measured using a magnetic balance. Each metal was embedded in a Ni-doped agarose gel phantom and the MR images of the metal-containing phantoms were taken using 1.5 and 3.0 T MR scanners under both fast spin echo and gradient echo conditions. 3-D renderings of the artifacts were constructed from the images and the artifact volumes were calculated for each metal. The artifact volumes of metals decreased with decreasing magnetic susceptibility, with the exception of Ag. Although Sn possesses the lowest absolute magnetic susceptibility (1.8 × 10−6), the artifact volume from Cu (−7.8 × 10−6) was smaller than that of Sn. This is because the magnetic susceptibility of Cu was close to that of the agarose gel phantom (−7.3 × 10−6). Since the difference in magnetic susceptibility between the agarose and Sn is close to that between the agarose and Ag (−17.5 × 10−6), their artifact volumes were almost the same, although they formed artifacts that were reversed in all three dimensions.