Magnetic field mapping around metal implants using an asymmetric spin-echo MRI sequence

Magnetic susceptibility of materials that are used for body implants causes much distortion in MR images. This paper deals with mapping the magnetic field induction in the vicinity of these materials. A modified spin-echo method is used, in which via inserting a time interval of a defined length the range of phase modulation is reduced below the value 2π. Even with a large B0 inhomogeneity it is not necessary to unwrap the phase jumps. The method is suitable for studying the effects of body-implant materials on MR images and for measuring their magnetic susceptibility.

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