Evaluation of Harmonic Signals Derived From Multiple Spatially Separated Samples for Magnetic Particle Imaging

We studied the harmonic components of signals derived from magnetization of magnetic nanoparticles depending on the direct current magnetic field at magnetic particle imaging (MPI). When single sample was located, the field free point confirmed that the third harmonic has the maximum value and the second harmonic has the minimum value. We proposed a new analytical method that takes the ratio of the third harmonic to the second harmonic to improve the resolution. Moreover, the complex signal obtained from separately located two samples was measured under a gradient magnetic field. We discussed the important issues with respect to the even harmonics in application of MPI for diagnostics in human body.