Magnetic resonance imaging for the determination of magnetic susceptibility of materials.

A magnetic resonance imaging method for volume magnetic susceptibility estimate of materials immersed in a liquid containing resonant nuclei is proposed. The method uses either the standard spin-echo Fourier imaging technique or the projection-reconstruction technique. Image distortions of cylindrical macroscopic susceptibility inhomomogeneities are analyzed and a correlation is established between the susceptibility value and the size of image deformation along the read gradient. For measurements, the susceptibility of the liquid surrounding the sample (here deionized water) serves as a reference, and characteristic distances between particular points, usually highlights in the distorted image, are related to the susceptibility difference between the two media. Different samples, mainly prosthetic materials with a large susceptibility range from 5 to 200 ppm in absolute value, have been investigated, and the accuracy of susceptibility determination is discussed.