[Removal of high signal artifact (marching metal artifact) by the magnetic substance].

During this project, we evaluated methods to prevent high-signal artifact (marching metal artifact) that are caused by magnetic substance. Marching metal artifact is caused by the resonance frequency created by magnetic substance. Phase encoding and frequency encoding are often switched to minimize the influence that marching metal artifact have on the image. However, this method will only change the position at which marching metal artifact occur. It does not have the ability to completely prevent marching metal artifact. Our research illustrated that marching metal artifact can be prevented by changing the strength of the slice selective gradient field at the 90 degree RF pulse and 180 degree RF pulse. In other words, marching metal artifact can be prevented by changing the frequency bandwidth for the 90 degree RF pulse and 180 degree RF pulse. The incorporation of the phase correct option in the device used for our research (SIGNA LX and SIGNA CV/i) results in different slice selective gradient field strengths at the 90 degree RF pulse and the 180 degree RF pulse. This indicates that the use of phase correction enables marching metal artifact to be prevented.