Global spatial normalization of human brain using convex hulls

Jack L. Lancaster, Peter T. Fox, Hunter Downs, Daniel S. Nickerson, Trish A. Hander, Mohammed El Mallah, Peter V. Kochunov, Frank Zamarripa

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

Global spatial normalization transforms a brain image so that its principal global spatial features (position, orientation and dimensions) match those of a standard or atlas brain, supporting consistent analysis and referencing of brain locations. The convex hull (CH), derived from the brain's surface, was selected as the basis for automating and standardizing global spatial normalization. The accuracy and precision of OH global spatial normalization of PET and MR brain images were evaluated in normal human subjects. Methods: Software was developed to extract OHs of brain surfaces from tomographic brain images, Pelizzari's hat-to-head least-square-error surface-fitting method was modified to fit individual CHs (hats) to a template CH (head) and calculate a nine-parameter coordinate transformation to perform spatial normalization. A template OH was refined using MR images from 12 subjects to optimize global spatial feature conformance to the 1988 Talairach Atlas brain. The template was tested in 12 additional subjects. Three major performance characteristics were evaluated: (a) quality of spatial normalization with anatomical MR images, (b) optimal threshold for PET and (c) quality of spatial normalization for functional PET images. Results: As a surface model of the human brain, the CH was shown to be highly consistent across subjects and imaging modalities. In MR images (n = 24), mean errors for anterior and posterior commissures generally were <1 mm, with SDs < 1.5 mm. Mean brain-dimension errors generally were <1.3 mm, and bounding limits were within 1-2 mm of the Talairach Atlas values. The optimal threshold for defining brain boundaries in both 18F-fluorodeoxyglucose (n = 8) and 15O-water (n = 12) PET images was 40% of the brain maximum value. The accuracy of global spatial normalization of PET images was shown to be similar to that of MR images. Conclusion: The global features of CH-spatially normalized brain images (position, orientation and size) were consistently transformed to match the Talairach Atlas in both MR and PET images. The OH method supports intermodality and intersubject global spatial normalization of tomographic brain images.

Original languageEnglish (US)
Pages (from-to)942-955
Number of pages14
JournalJournal of Nuclear Medicine
Volume40
Issue number6
StatePublished - Jun 1999

Keywords

  • Convex hull
  • Global spatial normalization
  • Regional spatial normalization
  • Talairach Atlas

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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