A NEW SEMIAUTOMATED, 3-DIMENSIONAL TECHNIQUE ALLOWING PRECISE QUANTIFICATION OF TOTAL AND REGIONAL CEREBELLAR VOLUME USING MRI

A new method was developed to measure total and regional cerebellar vo lumes using MRI, Previously, the volumes of the cerebellum and its sub structure had been studied planimetrically. The new method uses three- dimensional semiautomated volumetry with focus on reliability and perf ormance. The method consists of a manual presegmentation using landmar k-adjusted planes followed by region-growing segmentation and calculat ion of volume. The cerebellum is partitioned into 11 regions defined b y planes, which are adjusted for internal cerebellar landmarks (three radial regions inside the vermis that extend into the medial hemispher e tone-fourth of the transverse diameter of the hemisphere); one regio n in the lateral hemisphere (remaining three-fourths)). Forty-six heal thy volunteers were examined and the effects of age, gender, and symme try were estimated. Shrinkage in the vermis (especially anterior super ior compartment) was marked. Age effects diminished laterally and were not observed in the lateral hemisphere. Age effects on the total cere bellar volume were marginal. Effects of gender and symmetry were nonsi gnificant, Technique and results are discussed and related to methods and findings of others.