Correlating the Evans index and bicaudate index with ventricle volume at the three kinds of scanning baselines

Evans' Index (EI) and Bicaudate Index (BCI), as two-dimensional linear indexes, are commonly used to evaluate ventricle size. This study is investigated the differences in linear measures at the three kinds of scanning baselines and their correlations with ventricle volume.

In 186 healthy volunteers,117 hydrocephalus patients with complete skull and 72 hydrocephalus patients without complete skull, the linear indexes, intracranial volume and ventricle volume were calculated by 3D Slicer. Wilcoxon rank test was used for comparisons of the linear indexes at the scanning baselines respectively. Spearman analysis was applied for the correlations between linear indexes and ventricle volume respectively.

There were statistical differences in the linear indexes of the three scanning baselines. Comparison of the linear indexes in people from three groups, the difference of linear indexes was minimum at Reid's base line (RBL), but max at supraorbitomeatal line (SML). Compared with the third and the fourth ventricle, the linear indexes had a stronger correlation with lateral ventricle volume or total ventricle volume. On the other hand, EI at RBL had a stronger correlation with ventricle volume, compared with other two kinds of scanning baselines.

For consistent and representative linear measurements, we recommend using the Evans Index at Reid's baseline (RBL). However, the correlations between linear indices and ventricular volume were only modest, underscoring the limitation of 2D indices for precise volumetric assessment.