A quantitative study of the pixel-shifting, blurring and nonlinear distortions in MRI images caused by the presence of metal implants.

Magnetic resonance imaging has found an increasing number of medical applications in recent years due to its technical merits as well as its non-invasive nature. However, its full potential has been severely limited by magnetic susceptibility difference artefacts caused by the presence of ferromagnetic sources such as orthopedic implants, dental work or metallic needles used in neurosurgery. In this study, we propose a method to numerically quantify the distortions resulting from the magnetic susceptibility differences by investigating the phenomena from three perspectives: (1) pixel displacement, (2) blurring and (3) nonlinearity. For this purpose, phantom images obtained from a magnetic resonance scanner were studied. Attempts made to reconstruct an ideal image from its distorted version by appropriately compensating for the three types of distortions yielded encouraging results.