[A quantitative study of brain atrophy on computed tomography--multivariate analysis for comparison between the linear measurement method and the pixel count method].

We previously reported the newly developed quantitative measurement of the cerebral atrophy. The data indicated that the volume of the cerebrospinal fluid not always gradually increases during the life course but remains relatively constant until age 50 and thereafter increases with a wide variation. Though the technique, which is called the pixel count method, is highly quantitative, it is quite troublesome as it needs the computer to count out each pixels. On the other hand, the linear measurement method is easier than the pixel count method, but is far less quantitative. We examined seventy four subjects using both the linear measurement method and the pixel count method, and compared them by means of the multivariant analysis. Three different linear measurement methods were selected by the stepwise multiple regression analysis, those are B (distance between the caudate nuclei), E (greatest distance between the lateral ventricles at the level of the cella media) and G (number of visible sulci whose width are more than 3.1 mm at the level of 3 cm above the corpus callosum). B and E were calibrated by the maximum internal width of the skull (H). The highest correlation was achieved with a formula employing these parameters as follows; y = 42.66 X B/H + 12.52 X E/H + 0.232 X G - 2.92 (y means the estimated value of the CCR (CSF-cranial ratio), which is obtained by dividing the CSF volume by the cranial cavity). Multiple correlation coefficient was 0.76, and was statistically significant (p less than 0.001). The authors emphasized that using this formula we can easily predict CCR as the index of the brain atrophy without any computer.