RESUMO
INTRODUCTION: Visualization of passive devices during MRI-guided catheterizations often relies on a susceptibility artifact from the device itself or added susceptibility markers that impart a unique imaging signature. High-performance low field MRI systems offer reduced RF-induced heating of metallic devices during MRI-guided invasive procedures, but susceptibility artifacts are expected to diminish with field strength, reducing device visualization. In this study, field strength and orientation dependence of artifacts from susceptibility markers and metallic guidewires were evaluated using a prototype high-performance 0.55 T MRI system. MATERIALS AND METHODS: Artifact volume from nitinol and stainless steel passive susceptibility markers was quantified using histogram analysis of pixel intensities from three-dimensional gradient echo images at 0.55 T, 1.5 T and 3 T. In addition, visibility of commercially available clinical catheterization devices was compared between 0.55 T and 1.5 T using real-time bSSFP in phantoms and in vivo. RESULTS: A low-tensile strength stainless-steel marker produced field strength- and orientation-dependent artifact size (1.7 cm3, 1.95 cm3, 2.21 cm3 at 0.55 T, 1.5 T, 3 T, respectively). Whereas, a high-tensile strength steel marker, of the same alloy, produced field strength- and orientation-independent artifact size (3.35 cm3, 3.41 cm3, 3.42 cm3 at 0.55 T, 1.5 T, 3 T, respectively). Visibility of commercially available nitinol guidewires was reduced at 0.55 T, but imaging signature could be maintained using high-susceptibility stainless steel markers. DISCUSSION AND CONCLUSION: High-susceptibility stainless-steel markers generate field-independent artifacts between 0.55 T, 1.5 T and 3 T, indicating magnetic saturation at fields <0.55 T. Thus, artifact size can be tailored such that interventional devices produce identical imaging signatures across field strengths.