3D Printing of Subject-Specific Passive Shims for In Vivo Small-Animal Magnetic Resonance Imaging @Magnetic Resonance in Medicine

Magnetic resonance imaging (MRI) relies on a highly homogeneous B0 magnetic field to produce high-quality images. However, subject-specific inhomogeneities caused by magnetic susceptibility differences can degrade image quality and introduce artifacts, and these are often not adequately corrected by traditional active or passive shimming methods.

In this work, we introduce a new passive shimming approach to overcome these limitations: custom, subject-specific shims 3D-printed using a binder and a ferromagnetic ink. A custom algorithm calculates the optimal spatial distribution and concentration of ferromagnetic material within the shim, minimizing the standard deviation of the magnetic field. We demonstrate the full design and fabrication process for in vivo passive shimming of a rat brain, achieving a 21% improvement in magnetic field homogeneity and improved image quality in spin-echo echo-planar imaging scans, with a 65% increase in the Dice-Sørensen similarity coefficient. These results highlight the potential of combining computational optimization with additive manufacturing for effective, subject-specific passive shimming in MRI. Read our work here!