Elimination of water-soluble contrast media from the subarachnoid space. Investigation with computer tomography.

Contrast media injected into the subarachnoid space may be eliminated in two different ways, by diffusion through the meningeal membranes or by transport through these CSF pathways. The latter mode of transport may be examined using computer assisted tomography of the head. Diffusion predominants with contrast media of low molecular weight, such as methiodal sodium. The transport through the CSF cihculation increases when contrast media of high molecular weight such as meglumine iocarmate and metrizamide are used.