Artifacts in MRI of the temporomandibular joint caused by dental alloys: A phantom study at 1.5 T

Purpose: The influence of dental alloys on MRI of the temporomandibular joint was studied using a phantom model for this joint. Methods: At 1.5 T, 15 dental alloys and 14 of their most important components were investigated acquiring sagittal (FOV: 150 mm) and transverse (FOV: 250 mm) T-1-weighted SE images. In 11 cases, T-1- and T-2*-weighted FLASH images were measured additionally. The artifacts were assessed qualitatively as well as quantitatively, and the samples were subdivided into four artifact categories. Results: Ag, Cu, Ca, In, Ti, Sn, Zn, amalgam, the precious alloys, the Au-Pd and Ag-Pd alloys showed no artifacts (category I). Minimal artifacts below 10 mm on transverse images (category II) were found for Cr, Pd, Pt and for the Ni-Cr alloy. Mn and the remaining non-precious alloys induced artifacts up to 30 mm (category III). Significant artifacts - more than 30 mm - (category IV) were caused by Ni-Cr and 18/8 wires and by Co, Fe, and Ni. T-2*-weighted FLASH proved to be more susceptible for artifacts than T-1-weighted SE and FLASH techniques. Conclusions: In contrast to dental alloys for fixed prosthodontics, Ni-Cr- or 18/8 wires used for orthodontic bands can influence not only the image quality, but also the diagnostic reliability of MRI of the temporomandibular joint.