title: Tiny ferromagnetic intraocular foreign bodies detected by magnetic resonance imaging: a report of two cases.
abstract: We report two cases with tiny ferromagnetic intraocular foreign bodies (FBs) that were demonstrated only on magnetic resonance imaging (MRI) and confirmed by subsequent ophthalmologic operation. Both of the patients had a history of ocular trauma and their clinical symptoms were compatible with an intraocular FB. Plain x-ray film, 3 mm slice thickness computed tomography (CT) scans (Toshiba TXT 600 system and GERP22 system), B-scan ultrasonography, and an MRI study (Siemens Impact 1.0 MR system) were acquired. MR examinations were performed using spin-echo (SE) T1, T2, and PD-weighted axial and sagittal or coronal images with 3 mm slice thickness. Plain x-ray film, 3 mm slice thickness CT scans and B-scan ultrasonography all failed to demonstrate any tiny intraocular FBs in these two patients, whereas MRI revealed tiny ferromagnetic FBs due to their characteristic magnetic susceptibility artifact. A ferromagnetic FB was found in the vitreous body of each patient, which were 0.375x0.3x0.15 mm and 0.5x0.4x0.2 mm, respectively, and there was no evidence of MR-induced damage. We suggest that tiny ferromagnetic fragments with a diameter below 0.5 mm, which are too small to be visualized by x-ray plain films and CT images, may be visualized on MR images. These tiny ferromagnetic particles may not be large enough to cause ocular damage during a 1.0T MRI examination. MRI may be a useful tool in the evaluation of tiny intraocular ferromagnetic FBs if other imaging modalities such as plain s-ray, CT scan, and ultrasonography failed to do so. Further evaluation with a large-scale study (in vitro and in vivo animal study) for the safety of detecting tiny (<0.5 mm) intraocular ferromagnetic particles is warranted.
authors.affiliation: Department of Radiology, First Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan, PR China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Jingliang
authors.initials: J
authors.lastname: Cheng
authors.forename: Jie
authors.initials: J
authors.lastname: Bai
authors.forename: Cuiping
authors.initials: C
authors.lastname: Ren
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xuemei
authors.initials: X
authors.lastname: Gao
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Cui
authors.forename: Yun Jun
authors.initials: YJ
authors.lastname: Yang
mesh_terms: D000328:Adult; D016477:Artifacts; D005123:Eye / Q000000981:diagnostic imaging / Q000473:pathology; D005129:Eye Foreign Bodies / Q000175:diagnosis*; D015807:Eye Injuries, Penetrating / Q000150:complications / Q000601:surgery; D005290:Ferric Compounds; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D013508:Ophthalmologic Surgical Procedures; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology / Q000601:surgery; D014792:Visual Acuity
chemical_list: D005290:Ferric Compounds