One topic of interest for statisticians working on brain imaging is the analysis of statistical parametric maps. These images are acquired under different experimental conditions in different subjects. For example, subjects are scanned with PET and water labeled with O 15 to measure their cerebral blood flow under different experimental conditions.
Blood flow is known to be closely coupled to functional activation.
Therefore it is of interest to detect the areas where blood flow changes since they involved in the particular task the subject is practicing in the scanner. Given the noise levels of PET scanners, studies of this kind need to be performed on a number of different subjects. Images of the same subject are re-aligned among themselves and than coregistered with the correspondent MRI volume. The latter is then used to compute the nonlinear transformation that warps images of all subjects in a standardized reference space. The output of this kind of processing is a large set of locations, an image or a volume, where at each anatomical site corresponds a test statistic.