Standard brain spaces statistical parametric mapping and databases

A challenge for functional brain imaging is to maximize the detection of small signal changes whilst maintaining precision in the description of where signal change has occured.(23 and Many centres have approached these tasks, particularly for flow studies, by using one or more of the following: smoothing image data; stereotactic transformation of PET images, from individual subjects, into a standard brain space; and voxel by voxel analysis of signal change using statistical tests that account for the multiple comparisons made.

A standard brain space commonly used is that of Talairch and Tournoux. In this brain space, images are orientated in planes parallel to a transverse plane that passes through the anterior and posterior commisures. Thus, for example, images of regional cerebral blood flow from different subjects in an activation experiment can be transformed to match a template blood flow image in this space. The co-ordinates of signal change for the group can then be specified by co-ordinates in the x, y and z axes of the Talairch space allowing comparisons with other studies in other centres.

Voxel-by-voxel-based methods of image analysis, which reduce error variance and are devoid of observer bias, are now widespread. One such technique is statistical parametric mapping^4) which comprises realignment of images, spatial normalization, spatial smoothing, and voxel-wise statistical analysis. In the near future it is envisaged that a generic brain atlas database will be readily available in which PET, SPET, and functional MRI study results will be entered as standard co-ordinates allowing meta-analysis and easy comparison of results from different imaging centres.(4)

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