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

Abstract

BACKGROUND AND PURPOSE Orbital inflammatory syndrome (OIS) has clinical features that overlap with orbital lymphoid lesions and orbital cellulitis. Prompt diagnosis is needed in all 3 conditions because the management of each one differs greatly. CT and MR imaging, though useful, do not always distinguish among these conditions. The aim of this study was to identify the role of diffusion-weighted imaging (DWI) in differentiating these 3 diagnoses. MATERIALS AND METHODS A retrospective analysis of orbital MR imaging was conducted. T1- and T2-weighted and postcontrast images were analyzed. Region-of-interest analysis was performed by using measurements in areas of abnormality seen on conventional MR imaging sequences and measurements of the ipsilateral thalamus for each patient. The DWI signal intensity of the lesion was expressed as a percentage of average thalamic intensity in each patient. Similarly, lesion apparent diffusion coefficients (ADCs) and lesion-thalamus ADC ratios were calculated. Statistical significance was determined by the Kruskal-Wallis test, and post hoc pairwise comparisons, by the Mann-Whitney U test for DWI-intensity ratio, ADC, and ADC ratio. RESULTS A significant difference was noted in DWI intensities, ADC, and ADC ratio between OIS, orbital lymphoid lesions, and orbital cellulitis (P < .05). Lymphoid lesions were significantly brighter than OIS, and OIS lesions were significantly brighter than cellulitis. Lymphoid lesions showed lower ADC than OIS and cellulitis. A trend was seen toward lower ADC in OIS than in cellulitis (P = .17). CONCLUSIONS DWI may help differentiate OIS from lymphoid lesions and cellulitis and may allow more rapid management.

Diffusion Changes in the Vitreous Humor of the Eye during Aging

“…15,16 DWI has been a complementary technique useful in the differential diagnosis of orbital pathologies such as orbital inflammatory syndrome, orbital lymphoid lesion, orbital cellulitis, acute optic nerve infarction, endophthalmitis, acute ischemic homonymous hemianopsia, indeterminate orbital masses, and optic neuritis. [18][19][20][21][22][23] Also, Politi et al 24 recorded the ADC of the vitreous humor in healthy subjects as part of a normative data collection for a larger study of orbital masses and found a mean vitreal ADC that is significantly lower than that in our results; the difference might be due to different techniques used in the studies.…”

Single-Shot Turbo Spin-Echo Diffusion-Weighted Imaging for Retinoblastoma: Initial Experience

“…Recently, first applications of EP DWI in the orbit enabled successful differentiation of malignant (lymphoid) lesions, benign lesions, and inflammatory conditions. [11][12][13][14] In our study, we explored the potential of a non-EP DWI technique based on a HASTE sequence. Because the image acquisition is based on turbo spin-echo, it does not have image distortions and susceptibility artifacts present in EP-based techniques.…”

Diffusion-Weighted Imaging of Malignant Ocular Masses: Initial Results and Directions for Further Study

“…Several case series and case reports have used DWI to characterize orbital masses, inflammatory lesions, and infection; and additional scattered case reports are available describing the use of DWI to characterize ocular lesions such as endophthalmitis. [6][7][8][9][10] Isolated examples of DWI of retinoblastoma have also been reported (Castillo M, "More on DWI of Head and Neck Lesions" January 1, 2009; ajnrblog.org). 11 To our knowledge, there has not yet been a systematic analysis of ocular masses by using DWI.…”