Quantitative Volumetric Assessment of Orbital Soft Tissue
In orbital disease, exophthalmos, being the net effect of the volumetric changes of the soft tissues, is expressed as the distance between the cornea and the line connecting the lateral orbital margins (Hertel value). It does not explain, however, which tissues were responsible for the volumetric change. Because orbital soft tissues present with an inherent contrast due to the background of orbital fat on CT images, it was possible to apply interactive segmentation, as used in 3-D imaging, to sepatate the voxels belonging to these tissues. With voxel summation the volume could be calcualted of fat, muscle, globe, optic nerve and lacrimal gland, as well as that of the bony orbit. We have applied this technique to Graves’ ophthalmopathy and space-occupying orbital lesions (tumor volume calculation).
KeywordsOptic Nerve Lacrimal Gland Muscle Thickness Interactive Segmentation Orbital Disease
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