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B. Whitcher

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YNIMG Journal 2011 Journal Article

Image analysis and statistical inference in neuroimaging with R

  • K. Tabelow
  • J.D. Clayden
  • P. Lafaye de Micheaux
  • J. Polzehl
  • V.J. Schmid
  • B. Whitcher

R is a language and environment for statistical computing and graphics. It can be considered an alternative implementation of the S language developed in the 1970s and 1980s for data analysis and graphics (Becker and Chambers, 1984; Becker et al. , 1988). The R language is part of the GNU project and offers versions that compile and run on almost every major operating system currently available. We highlight several R packages built specifically for the analysis of neuroimaging data in the context of functional MRI, diffusion tensor imaging, and dynamic contrast-enhanced MRI. We review their methodology and give an overview of their capabilities for neuroimaging. In addition we summarize some of the current activities in the area of neuroimaging software development in R.

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YNIMG Journal 2008 Journal Article

Reproducibility of fMRI in the clinical setting: Implications for trial designs

  • R. Bosnell
  • C. Wegner
  • Z.T. Kincses
  • T. Korteweg
  • F. Agosta
  • O. Ciccarelli
  • N. De Stefano
  • A. Gass

With expanding potential clinical applications of functional magnetic resonance imaging (fMRI) it is important to test how reliable different measures of fMRI activation are between subjects and sessions and between centres. This study compared variability across 17 patients with multiple sclerosis (MS) and 22 age-matched healthy controls (HC) in 5 European centres performing an fMRI block design with hand tapping. We recruited subjects from sites using 1. 5 T scanners from different manufacturers. 5 healthy volunteers also were studied at each of 4 of the centres. We found that reproducibility between runs and sessions for single individuals was consistently much greater than between individuals. There was greater run-to-run variability for MS patients than for HC. Measurements of maximum signal change (MSC) appeared to provide higher reproducibility within individuals and greater sensitivity to differences between individuals than region of interest (ROI) suprathreshold voxel counts. The variability in measurements between centres was not as great as that between individuals. Consistent with these observations, we estimated that power should not be reduced substantially with use of multi-, as opposed to single-, centre study designs with similar numbers of subjects. Multi-centre interventional studies in which fMRI is used as an outcome measure thus appear practical even when implemented in conventional clinical environments.

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