Reliability of PET activation across statistical methods, subject groups, and sample sizes

Reliability of PET activation across statistical methods, subject groups, and sample sizes Four pixel‐based methods for estimating regional activation in positron emission tomography (PET) images were implemented so as to allow the comparison of their performances in the same dataset. Change distribution analysis, Worsley's method, a pixelwise general linear model, a nonparametric method, and several methods derived from them were investigated. Important technical factors, including the degree of smoothing, stereotactic transform, coregistration algorithm, search volume, and the volumetric alpha level, were held constant. The dataset, which was obtained with a verb generation paradigm, was large enough to permit assessment of concordance between independent samples of conventional size, as well assessment of within‐cohort replicability. (Eighteen normal subjects performed four GENERATE‐READ pairs each.) Same‐task (noise) images were also analyzed. In noise datasets, type I errors (false positives) occurred at the nominal rate (in 5% of datasets). Detected regions of activation were highly likely to be internally replicated (93%). The detected activations were a superset of activations previously reported using the same paradigm. The methods were chiefly distinguished by type II error rates and by the stability of the location of activation clusters. Those methods dependent on local variance estimates were less powerful with small sample sizes and less stable with respect to the attributed location of task‐induced changes. The use of pooled variance (Worsley's method) reduced these problems, but variance was not stationary. Overall, the power of all analyses was modest with samples of conventional size (nine subjects × one or two task‐pairs). Modeling of the sources of variance, particularly improvement of anatomical standardization, is likely to improve the power of pixel‐based analyses. © 1996 Wiley‐Liss, Inc. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Human Brain Mapping Wiley

Reliability of PET activation across statistical methods, subject groups, and sample sizes

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Publisher
Wiley
Copyright
Copyright © 1996 Wiley‐Liss, Inc.
ISSN
1065-9471
eISSN
1097-0193
DOI
10.1002/(SICI)1097-0193(1996)4:1<23::AID-HBM2>3.0.CO;2-R
pmid
20408184
Publisher site
See Article on Publisher Site

Abstract

Four pixel‐based methods for estimating regional activation in positron emission tomography (PET) images were implemented so as to allow the comparison of their performances in the same dataset. Change distribution analysis, Worsley's method, a pixelwise general linear model, a nonparametric method, and several methods derived from them were investigated. Important technical factors, including the degree of smoothing, stereotactic transform, coregistration algorithm, search volume, and the volumetric alpha level, were held constant. The dataset, which was obtained with a verb generation paradigm, was large enough to permit assessment of concordance between independent samples of conventional size, as well assessment of within‐cohort replicability. (Eighteen normal subjects performed four GENERATE‐READ pairs each.) Same‐task (noise) images were also analyzed. In noise datasets, type I errors (false positives) occurred at the nominal rate (in 5% of datasets). Detected regions of activation were highly likely to be internally replicated (93%). The detected activations were a superset of activations previously reported using the same paradigm. The methods were chiefly distinguished by type II error rates and by the stability of the location of activation clusters. Those methods dependent on local variance estimates were less powerful with small sample sizes and less stable with respect to the attributed location of task‐induced changes. The use of pooled variance (Worsley's method) reduced these problems, but variance was not stationary. Overall, the power of all analyses was modest with samples of conventional size (nine subjects × one or two task‐pairs). Modeling of the sources of variance, particularly improvement of anatomical standardization, is likely to improve the power of pixel‐based analyses. © 1996 Wiley‐Liss, Inc.

Journal

Human Brain MappingWiley

Published: Jan 1, 1996

References

  • Assessing the significance of focal activations using their spatial extent
    Friston, Friston; Worsley, Worsley; Frackowiak, Frackowiak; Mazziotta, Mazziotta; Evans, Evans
  • Statistical parametric maps in functional imaging: A general linear approach
    Friston, Friston; Holmes, Holmes; Worsley, Worsley; Poline, Poline; Frith, Frith; Frackowiack, Frackowiack
  • A new technique for PET slice orientation and MRI‐PET coregistration
    Grabowski, Grabowski; Damasio, Damasio; Frank, Frank; Hichwa, Hichwa; Boles Ponto, Boles Ponto; Watkins, Watkins
  • Cluster analysis in individual functional brain images: Some new techniques to enhance the sensitivity of activation detection methods
    Poline, Poline; Mazoyer, Mazoyer
  • Three‐dimensional analysis of clustered voxels in 15 O‐butanol brain activation images
    Roland, Roland; Levin, Levin; Kawashima, Kawashima; Akerman, Akerman

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