Calculation of cerebral tissue and cerebrospinal fluid space volumes from computer tomograms.

The volumes of the cerebral tissue, and internal and external cerebrospinal fluid spaces were calculated from the computer tomograms of 28 patients. On the basis of their different absorption coefficients, cerebral tissue and CSF space were outlines and their volumes calculated by computer. The ratio of cerebral tissue volume to CSF space volume was expressed as an index. This correlated well with an objective grading of severity of hydrocephalus. The index in patients without pathology was between 10.5 and 18.4. In cerebral atrophy the index was between 2.1 and 6.7 depending upon the severity. In occlusive hydrocephalus it was between 1.0 and 5.6. The changes in the volume of the CSF space after treatment can easily by demonstrated by appropriate changes in the index.