CNS Location	Criteria
Calvarium	CT Focal lytic or sclerotic lesion	MRI Marrow replacing process with focal enhancement
Pachymeninges	CT Iso- to hyperdense dural thickening with enhancement. Often difficult to appreciate by non-contrast examinations	MRI Sheet or nodular dural thickening and enhancement
Leptomeninges	CT Sulcal or basilar cisternal enhancement. Often difficult to appreciate by CT unless florid disease	MRI Sulcal, cisternal, or cranial nerve FLAIR hyperintensity and enhancement. Often diffuse and linear.
Parenchyma	CT Regional hypodenisty sparing the cortical margin. Variable degrees of enhancement following intravenous contrast. Non- hemorrhagic metastatic foci are often occult by non-contrast CT.	MRI Focal enhancing mass at the grey white matter junction associated with robust vasogenic edema. Edema spares the surrounding grey matter.

Note: Common CT and MR imaging appearance by location. Metastatic disease can appear varied based on disease etiology.