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AJNR - American Journal of Neuroradiology

Published ahead of print on October 8, 2008
doi: 10.3174/ajnr.A1315

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MR Imaging of Orbital Inflammatory Syndrome, Orbital Cellulitis, and Orbital Lymphoid Lesions: The Role of Diffusion-Weighted Imaging

R. Kapur^a, A.R. Sepahdari^b, M.F. Mafee^c, A.M. Putterman^a, V. Aakalu^a, L.J.A. Wendel^d and P. Setabutr^a

^a Departments of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Ill
^b Radiology, University of Illinois at Chicago, Chicago, Ill
^c Department of Radiology, University of California, San Diego, Calif
^d Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa

View larger version (106K): [in this window] [in a new window]   Fig 1. OIS (A–C) compared with reactive lymphoid hyperplasia (D–F). A, Axial T1-weighted fat-suppressed postcontrast image shows intense ill-defined enhancement within the postseptal and retrobulbar fat (arrow). B, Axial T2-weighted image shows low signal intensity in the area of enhancing abnormality (arrow). C, Axial ADC image shows moderate signal intensity within the lesion (arrow). Slight heterogeneity is noted, with a focal area of slightly lower ADC at the anterior aspect of the lesion (small arrow). D, Coronal T1-weighted fat-suppressed postcontrast image shows ill-defined enhancement extending throughout the upper extraconal soft tissue (arrow). E, Axial T2-weighted image shows low signal intensity within the area of enhancing abnormality (arrow). F, Axial ADC image shows relatively low signal intensity within the lesion compared with the OIS lesion in Fig 1D (arrow). Lymphoid lesion ADC intensity is similar to that of brain parenchyma, whereas the OIS lesion shows relatively increased ADC.

View larger version (109K): [in this window] [in a new window]   Fig 2. Orbital lymphoma (A–C) compared with OIS (D–F). A, Axial T1-weighted image shows a rounded isointense mass at the upper aspect of the orbit (arrow). B, Axial T2-weighted image shows isointense signal intensity–to-brain parenchyma (arrow). C, Axial DWI shows high signal intensity relative to brain parenchyma (arrow). D, Axial T1-weighted image shows an isointense ovoid intraconal mass (arrow). E, Axial T2-weighted image shows slight hypointensity compared with parenchyma (arrow). F, Axial DWI shows even greater hypointensity compared with brain parenchyma (arrow). Comparison of quantitative ADC also showed a difference between these lesions.

View larger version (108K): [in this window] [in a new window]   Fig 3. OIS in 2 patients (A–C, D–F), showing the relationship between lesion location and susceptibility artifact. A, Parasagittal oblique T1-weighted fat-suppressed postcontrast image shows ill-defined enhancement extending along the posterior globe and optic nerve (arrow). B, Axial T2-weighted image shows isointense signal intensity in the area of enhancing abnormality (arrow). C, Axial DWI shows moderate signal intensity in this area (arrow). D, Axial T1-weighted fat-suppressed postcontrast image shows linear irregular enhancement in the region of the orbital apex, extending along the optic nerve course and middle cranial fossa dural surface (arrow). E, Axial T2-weighted image shows hypointense signal intensity in this area (arrow). F, Axial DWI demonstrates susceptibility artifact that obscures the lesion (asterisk).

View larger version (146K): [in this window] [in a new window]   Fig 4. Comparison of a sarcoid lesion (A and B) with cellulitis (C and D). A, Axial T1-weighted fat-suppressed postcontrast image shows ill-defined enhancement throughout the retrobulbar and periorbital soft tissues (arrow). B, Axial DWI image shows moderate signal intensity throughout the area of enhancing abnormality (arrow). C, Axial T1-weighted fat-suppressed postcontrast image shows similar ill-defined retrobulbar and periorbital enhancement (arrow). D, Axial DWI shows uniform low signal intensity throughout the area of abnormal enhancement (arrow).

View larger version (78K): [in this window] [in a new window]   Fig 5. Orbital cellulitis related to mucormycosis (A–C) and bacterial infection (D–F). A, Axial T1-weighted fat-suppressed postcontrast image shows an opacified right maxillary sinus and extensive enhancement throughout the infratemporal fossa tissues, involving the pterygoid muscles (arrow). B, Axial exponential ADC image shows low intensity throughout these tissues (arrow), indicating relatively increased ADC, best appreciated by comparison with the contralateral side. The area of restricted diffusion behind the right maxillary sinus represents abscess. C, Axial exponential ADC image through the orbit shows restricted diffusion within the infarcted posterior right optic nerve (arrow). D, Axial T1-weighted fat-suppressed postcontrast image shows intense enhancement within the periorbital soft tissue (arrow). E, Axial T2-weighted image shows moderate hyperintensity relative to extraocular muscle. F, Axial exponential ADC image slightly lower shows increased ADC throughout the region of nonspecific enhancement (arrow). Restricted diffusion is seen within an abscess (a), which corresponds with a nonenhancing T1 hypointense area. Diffusion is not restricted within the tissues immediately surrounding the focal abscess. G, Axial T1-weighted fat-suppressed postcontrast image shows no enhancement within an abscess (a), with marked enhancement in the area of cellulitis.

View larger version (16K): [in this window] [in a new window]   Fig 6. Graph shows lesion-thalamic DWI intensity ratio in patients with orbital lymphoid lesions, OIS, and orbital cellulitis. The mean for each group is given, and a vertical bar depicts the range for each lesion. Orbital lymphoid lesions demonstrate the brightest signal intensities, and OIS lesions are brighter than orbital cellulitis.