| Popis: |
Intracranial volume (ICV) is an important adjustment factor in many volumetric brain studies. Several different methods exist for computing ICV based on structural MR images and estimates are known to vary between methods. These methods can be broadly classified as either voxel-based, where the compartments within the skull are segmented and the ICV is calculated as a voxel count, and registration-based, where the scaling factor of a transformation to a common template is used as a proxy for ICV. While most previous studies report no age-related changes to ICV beyond adolescence or young adulthood, a few studies find decreasing ICV with increasing age in adults (0.1-0.3% decrease per year). However, the effect of the ICV estimation method on age trajectories is not well characterised, and it has been suggested that registration-based ICV measures may be susceptible to age-dependent bias due to brain atrophy. In this study, we estimate ICV using two voxel-based ICV measures (SPM12 and CAT12) and two registration-based ICV measures (FreeSurfer v6.0.0 and FSL 5.0.9) in a cross-sectional sample of healthy adolescents, adults, and elderly controls. We examine the test-retest reliability, correlation, and agreement between estimation methods, test for the presence of age effects and investigate if any effects are dependent on the type of ICV estimation method. |
