Format

Send to:

Choose Destination
See comment in PubMed Commons below
Psychiatry Res. 2011 Aug 30;193(2):113-22. doi: 10.1016/j.pscychresns.2011.01.007.

Statistical adjustments for brain size in volumetric neuroimaging studies: some practical implications in methods.

Author information

  • 1Department of Mathematics and Statistics, Colby College, Waterville, ME 04901, USA. lobrien@colby.edu

Abstract

Volumetric magnetic resonance imaging (MRI) brain data provide a valuable tool for detecting structural differences associated with various neurological and psychiatric disorders. Analysis of such data, however, is not always straightforward, and complications can arise when trying to determine which brain structures are "smaller" or "larger" in light of the high degree of individual variability across the population. Several statistical methods for adjusting for individual differences in overall cranial or brain size have been used in the literature, but critical differences exist between them. Using agreement among those methods as an indication of stronger support of a hypothesis is dangerous given that each requires a different set of assumptions be met. Here we examine the theoretical underpinnings of three of these adjustment methods (proportion, residual, and analysis of covariance) and apply them to a volumetric MRI data set. These three methods used for adjusting for brain size are specific cases of a generalized approach which we propose as a recommended modeling strategy. We assess the level of agreement among methods and provide graphical tools to assist researchers in determining how they differ in the types of relationships they can unmask, and provide a useful method by which researchers may tease out important relationships in volumetric MRI data. We conclude with the recommended procedure involving the use of graphical analyses to help uncover potential relationships the ROI volumes may have with head size and give a generalized modeling strategy by which researchers can make such adjustments that include as special cases the three commonly employed methods mentioned above.

Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

PMID:
21684724
[PubMed - indexed for MEDLINE]
PMCID:
PMC3510982
Free PMC Article
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science Icon for PubMed Central
    Loading ...
    Write to the Help Desk