Penetration of the brain by nonionic water soluble tri- and hexaiodinated contrast media. Experimental autoradiographic study of two contrast media: Iotrol and Iopamidol labelled with iodine 125.

After suboccipital injection of Iotrol and Iopamidol labelled with iodine 125 in rabbits, we measured residual radioactivity in the whole brain and optical density on autoradiographs of brain sections obtained 2, 8 and 24 h after injection. Residual radioactivity is higher with Iotrol than with Iopamidol after 8 h and 24 h. At densitometry, while the penetration of the cortex is the same with both media at 2 h (although subcortical passage of Iotrol is greater), by 8 h the concentration of Iopamidol is twice that of Iotrol, and at 24 h it is three times as high. A similar pattern was seen in the subcortical region. These densitometric findings are in agreement with previous electrophysiological studies, in which changes were less severe and more transient with Iotrol than with Iohexol. There is nevertheless an apparent lack of agreement between the studies of radioactivity and the electrical findings. The lower neurotoxicity of Iotrol may be explained by: a longer half-life in the subarachnoid space; its larger molecules, which inhibit diffusion in the extracellular fluid, and its more hydrophilic nature, which reduces intracellular penetration.