Region of interest issues: the relationship between structure and function in the brain.

The comparison of data sets from individual subjects between imaging modalities is necessary in order to evaluate the normal physiologic responses of the brain or the pathophysiological changes that accompany disease states. Similarly, it is critical to compare data between individuals both within and across imaging modalities. In a collaborative project with a number of university groups, we have developed a system that allows for the within-subject alignment and registration of three-dimensional data sets obtained from different modalities for the same individuals. These data make use of proposed criteria for the optimal solution to positron emission tomography image acquisition and analysis originally established through a series of international workshops. The analysis takes into account errors induced by image acquisition, registration, and alignment with regard to scaling, translation, and rotation. Using the principles of morphometrics and homologous landmarks, the between-subject warping of individual brain anatomy to match that of other individuals, groups or an idealized model can be obtained. Resultant information can provide averaged between-subject data for populations of normal individuals or patients with specific neurologic disorders. Such a system, provides the means by which to compare objectively quantitative data between individuals in a highly automated fashion.