Influence of medical metal implants in the craniofacial area on the accuracy of quantitative magnetic resonance relaxometry within brain-related ranges at 3 T

<i>Objective.</i>To evaluate how medical metal implants influence<i>T</i>₁and<i>T</i>₂mapping in magnetic resonance imaging (MRI), focusing on relaxation quantification accuracy and repeatability.<i>Approach.</i>The National Institute of Standards and Technology/International Society for Magnetic Resonance in Medicine phantom was scanned on three 3 T MRI systems at different sites using variable flip angle (VFA), multi-echo fast spin echo (ME-FSE), and MR fingerprinting (MRF). Repeatability and accuracy were assessed, followed by analysis of the effects of aneurysm clips, cranial plates, and orthodontic materials.<i>Main results.</i>Coefficient of variation of 2.44%-10.81% for VFA/ME-FSE and 1.67%-16.31% for MRF. Deviations from reference values ranged from 5.96%-132.26% for VFA/ME-FSE and -36.87%-17.17% for MRF. When metal implants were introduced, VFA remained more robust for<i>T</i>₁mapping while MRF and ME-FSE only quantified spheres distal to the metal reliably.<i>B</i>₀/<i>B</i>₁⁺mapping sequence effectively delineated artifact boundaries and guide reliable regions for relaxometry imaging.<i>Significance.</i>Medical metal implants can substantially affect relaxation quantification in MRI, with distortion severity depending on implant type and distance. These findings highlight the importance of accounting for these effects when interpreting quantitative MRI results in both clinical and research settings.