Proof-of-Concept Simulation Study: An Open-sided Hybrid MPI and Low-Field MRI Scanner

Abstract

This work aims to investigate the feasibility of performing hybrid magnetic particle imaging (MPI) and low-field magnetic resonance imaging (MRI) on our in-house preclinical open-sided MPI prototype system. The primary advantage of the system lies in the interchangeable use of coil groups between MPI and MRI modes, facilitating the generation of a hybrid image that features high sensitivity and contrast imaging of magnetic nanoparticle distribution by MPI, together with the anatomical information from MRI. In the prototype system, the selection field of MPI is generated via two bi-planar gradient coil groups, producing a Field-Free Line (FFL) in the xy-plane. These coil groups generate the gradient fields in x- and y-directions in MRI mode. A coil group in Helmholtz configuration produces the focus field in MPI mode, while generating the main static B₀ field in z-direction in MRI mode. Another coil group creates the drive field when used in Helmholtz configuration in MPI mode, and provides the z-gradient field when used in Maxwell configuration in MRI mode. In this work, experimental measurements were conducted to obtain magnetic field maps for all coil groups. The acquired field maps reveal that the system creates an FFL featuring a 0.3 T/m gradient for MPI mode and B₀ field ranging from 5 mT to 65 mT , exhibiting approximately 3500 ppm inhomogeneity for low-field MRI mode. Simulations performed using the measured fields affirm the capability of the system to perform hybrid MPI and low-field MRI imaging.