Influence of signal bandwidth and phase delay on complex susceptibility based magnetic particle imaging

In this paper, the influences of signal bandwidth and phase delay on the spatial resolution of complex susceptibility based magnetic particle imaging (csMPI) are investigated by modeling the transfer function of the measurement circuit. Based on the simulation and experimental results, it is found that the signal bandwidth and the phase delay will significantly impact on the spatial resolution of csMPI. To avoid the influence of narrow signal bandwidth and phase delay of measurement circuit on csMPI, a resonance measurement circuit with −3 dB bandwidth of 2.3 kHz (much larger than the signal bandwidth of the desired csMPI signal) and resonance frequency of 12.8 kHz is adopted to measure the weak nonlinear magnetization of the magnetic nanoparticles; a phase compensation is used when calculating the real and the imaginary components of ac magnetic susceptibility.