3D Printing of Subject‐Specific Passive Shims for In Vivo Small‐Animal Magnetic Resonance Imaging

PURPOSE: magnetic field to generate high-quality images. However, subject-specific inhomogeneities, induced by magnetic susceptibility differences, can degrade image quality and cause artifacts and are often inadequately corrected by traditional active or passive shimming methods. This work aims to create a new passive shimming method to overcome these problems. METHOD: This study introduces an innovative approach to developing custom, subject-specific passive shims 3D-printed with a binder and a ferromagnetic ink. The optimal spatial distribution and concentration of ferromagnetic material within the shim are calculated using a custom algorithm that minimizes the magnetic field standard deviation. RESULTS: The shim design and fabrication process is demonstrated for in vivo passive shimming of a rat brain, yielding 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. CONCLUSION: This approach highlights the potential of combining computational optimization with additive manufacturing for effective, subject-specific passive shimming in MRI.