Effects of spatial transformation on regional brain volume estimates

Abstract

Spatial transformation of MR brain images is a standard tool used in automated anatomical parcellation and other quantitative and qualitative methods to assess brain tissue volume, composition, and distribution. Despite widespread use, the quantitative effects of spatial transformation on regional brain volume estimates have been little studied. We report on the effects of transformation on regional brain volumes of 38 (17M, 21F) manually parcellated brains. After tracing in native space, regions of interest were transformed using a classic piecewise linear Talairach transformation (Tal) or a nonlinear registration (AIR 5 th order nonlinear algorithm, 158 parameters) to one of three Talairach-based templates: 1) Tal50, constructed from 50 Talairach-transformed normal brains, 2) the MNI 305 atlas, 3) IA38, constructed from MNI305-transformed scans of the 38 subjects used in this study. Native volumes were compared to the transformed volumes. We found that: 1) significant group level differences can be obtained in transformed data sets that are in the opposite direction of effects obtained in native space; 2) the effects of transformation are heterogeneous across brain regions, even after covarying for total brain volume and age; 3) volumetric intra-class correlations between native and transformed brains differ by registration method and template choice, region, and tissue type; and 4) transformed brains produced hippocampus and corpus callosum volume proportions that were significantly different from those obtained in native space. Our results suggest that region-based volumetric differences uncovered by spatial-transformation-based methods should be replicated in native-space brains, and that metaanalyses should take into account whether volumes are determined using spatially-transformed images and/or specific automated methods.

Ventral aspect of the visual form pathway is not critical for the perception of biological motion

“…EBA partitions: v-EBA, aspect of EBA ventral to MT/V5; mt-EBA, aspect of EBA overlapping MT/V5; a-EBA, aspect of EBA anterior to MT/V5 (46,47). *GB's, CR's, and EC's lesion sizes were approximated on an MNI template brain and therefore provided in MNI normalized space units (mm 3 ), which might be an overestimation relative to native space volume (82). pSTS and vPMC are critical for biological motion perception (11,15,16,41,62,63), we speculate that the ventral regions of the form visual pathway are critical for recognizing the person performing the movement, but not for recognizing the motion being performed.…”

Hippocampal Shape Deformation in Female Patients with Unremitting Major Depressive Disorder

“…This asymmetric characteristic has been reported previously in the normal male brain, but not in the female brain. 24,25 The hippocampal asymmetry of the healthy human is debatable, because some articles have reported hippocampal asymmetry, 26,27 whereas others have reported hippocampal symmetry. [28][29][30][31] The present study seems to support the hypothesis that hippocampal volume is not asymmetric in healthy women.…”

Disease classification: A probabilistic approach

“…A recent study by [7] has shown that registration can introduce unwanted effects in the data set. In this work, we avoid the errors accrued during registration by using a probability density based classifier.…”

“…However, as has been shown by the authors in [7], transforming the images from subject space to atlas space can significantly change certain quantities under study (for example, volume). Thus, errors accrued during registration are carried forward in subsequent analysis, in particular in classification tasks.…”