Spatially-selective RF pulse design for magnetic resonance imaging of samples including conductive implants

Abstract

Magnetic resonance imaging (MRI) applies radiofrequency (RF) electromagnetic field to scan human bodies. Quantitative evaluations of MRI images are difficult due to the interference between the RF field and conductive implants. In this study, we designed RF pulses for mitigating the inhomogeneity of signal intensities in MRI image induced by interference between RF field and conductive implants. The adaptive RF pulse was calculated by analyzing the Bloch equation inversely. We carried out MRI simulation with a numerical model of inhomogeneous signal intensities. The homogeneity of signal intensities was improved by applying the adaptive RF pulse in the simulation results. We could determine the spatial resolution and excitation field of view (FOV) by changing the amplitude and the number of oscillating gradient field, respectively. The effectiveness of the designed RF pulse waveform was evaluated by performing numerical simulation and experiments with metallic implants.