Linear and Shift Invariance of Magnetic Particle Imaging

Abstract

MPI is intrinsically a linear and shift-invariant (LSI) system as described in x-space theory [3,4] assuming perfect signal acquisition and that the imaging equation can be written as a convolution in realspace. However, the received MPI signal is corrupted by a direct feedthrough signal from the excitation source at the drive frequency, which is 10⁶ times larger than the nanoparticle signal. Hardware filtering is required to suppress the feedthroughsignalbutalso inevitably removes this frequency component from the particle signal. This signal loss in the received particle signalbreaks the LSI propertiesof x-space MPI. This study will investigate the impact of losing the fundamental frequency component in the image domain and propose an algorithm to recover the lost information. Finally, experimental results demonstrate that LSI propertiescan be restored after applying a simple and robust baseline recovery algorithm.