Improved metal suppression using new generation low-field MRI: a biophantom feasibility study.

Abstract

Novel 0.55 MRI scanners have the potential to reduce metal artifacts around orthopedic implants. The purpose of this study was to compare metal artifact size and depiction of anatomy between 0.55T and 3.0T MRI in a biophantom. Steel and titanium screws were implanted in 12 porcine knee specimens and imaging at 0.55T and 3T MRI was performed using the following sequences: turbo spin-echo (TSE), TSE with view angle tilting (VAT), and slice encoding for metal artifact correction (SEMAC) with proton-density (PD) and T2-weighted short-tau inversion-recovery (T2w-STIR) contrasts. Artifacts were measured, and visualization of anatomy (cartilage, bone, growth plates, cruciate ligaments) was assessed and compared between groups. Metal artifacts were significantly smaller at 0.55T. The smallest artifact sizes were achieved with SEMAC at 0.55T for both PD and T2w-STIR sequences; corresponding relative size reductions vs. 3.0T were 78.7% and 79.4% (stainless steel) and 45.3% and 1.4% (titanium). Depiction of anatomical structures was superior at 0.55T. Substantial reduction of artifact size resulting in superior depiction of anatomical structures is possible on novel 0.55T MRI systems. Further clinical studies are required to elucidate patient-relevant advantages.