An improved point spread function for complex susceptibility-based magnetic particle imaging

Spatial resolution is a key metric for characterizing magnetic particle imaging (MPI), and magnetic relaxation is a critical factor affecting the spatial resolution. This study investigates the point spread functions (PSFs) of MPI and analyzes the potential of breaking through the spatial resolution limit, which equals the full width at half maximum (FWHM) of the Langevin function derivative. In this work, different PSFs of MPI were built based on the magnitude and real and imaginary parts of complex susceptibility. The imaging performance was evaluated using the FWHM and a self-defined convergence parameter. The results show that image reconstruction can achieve a narrower PSF based on the imaginary part of complex susceptibility, and the heavy-tailed distribution of the derivative of the Langevin curve can be optimized. This suggests that there is scope to improve the spatial resolution and image contrast of MPI.