Magnetic resonance imaging in preseptal ferromagnetic foreign bodies

To review the literature on safety of magnetic resonance imaging (MRI) in patients with preseptal ferromagnetic foreign bodies.

We describe 3 cases of MRI in patients with preseptal ferromagnetic foreign bodies (FFBs) from our institution.

The FFBs were all preseptal, adjacent to the medial canthus (n = 2) and lateral canthus (n = 1). None of the patients had any ocular complications post-MRI. The literature review identified an additional 7 cases with intraocular and preseptal FFBs that underwent MRI. The FFBs ranged in size from 1.0 mm to 3.5 mm. The FFBs were intraocular (n = 6), or preseptal (n = 1). The MRI field strength ranged from 0.35 T to 1.5 T. Five (83.3%) of the patients with intraocular FFBs had ocular complications, which included hyphema (n = 2), cataract (n = 3), vitreous haemorrhage (n = 1), and corneal scar (n = 1). The patient with preseptal FFB did not have post-MRI complications.

There is some evidence to suggest that patients with preseptal FFBs may be less likely to experience complications post-MRI compared to intraocular FFBs. Various factors affect the safety of MRIs, including FFB location, size, proximity to visually-significant structures, and MRI field strength.