The ventricular-brain ratio on computed tomography scans: validity and proper use.

The planimetric measurement of the area of the ventricles on a computed tomographic section is a convenient and useful method of assessing ventricular size when more sophisticated techniques are not available. It is commonly reported as a planimetric ventricular-brain ratio or VBR. Ventricular size is related to cranial size in normal adults which provides a rationale for the use of a ratio of areas. The ratio might not be an appropriate measure to use when studying conditions acquired in childhood. Guidelines are suggested for the use of planimetric methods to prevent bias in the experimental results.