Answer:
Patrick De Potter, in Clinical Ophthalmic Oncology, 2007
Content
Information on the content of the lesion (cystic or solid; homogeneous or heterogeneous) can be obtained by both CT and MR imaging techniques. Both techniques also detect the presence of fluid–fluid or fluid–air levels. When lesion density is higher than that of the vitreous, CT images identify the lesion as solid. As wide range of tissue densities on CT scans or signal intensities on MR images relate to the internal architecture and the presence of proteinaceous or blood products, it is not always possible to differentiate a solid from a cystic orbital lesion. MRI images identify tissue compounds such as melanin, methemoglobin, deoxyhemoglobin, ferritin, and proteinaceous material. Punctate or conglomerate increased densities on CT scans or foci of signal void on MRI may be seen in trauma, vascular tumors, optic nerve sheath tumors (meningioma), epithelial lacrimal gland tumors, and malignant osseous tumors (osteosarcoma). In general, MR images provide more information about the content of the lesion and than do CT images. However, CT is best suited for the detection of calcification.