Region of Interest Issues: The Relationship between Structure and Function in the Brain

Abstract

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.

Fast Nonsupervised 3D Registration of PET and MR Images of the Brain

“…Validation studies using a dedicated brain shaped phantom have shown that the maximum registra tion error was of the order of the PET pixel size (2 mm) for the wide variety of tested configurations. The soft ware is routinely used today in a clinical context by the physiCians of the Service Hospitalier Frt!deric loliot which rely on the identification of external or inter nal landmarks by an expert in anatomy (Bookstein, 1991;Ende et aI., 1991;Lemoine et aI., 1991) or on interactive tools allowing a manual registration based on visual criteria (Pietrzyk et aI., 1990;Evans et aI., 1991;Greitz et aI., 1991), are more satisfac tory but may suffer from lack of reproducibility. Therefore, semiautomatic retrospective methods have been proposed to register 3D medical images containing a relatively rigid portion of the human body.…”

A methodology for specifying PET VOIs using multimodality techniques

“…For example, in typical VOI's of cortical grey matter, there is both spill out of grey matter activity within the borders of the region as well as spill in from the activity of nearby grey and white matter. One approach to dealing with this problem is to define regions well within the anatomical borders to avoid the spillover effects on the boundaries [27], [28]. Indeed as was seen in Fig.…”

Comparison of five cluster validity indices performance in brain [18F]FET‐PET image segmentation using k‐means

“…Positron emission tomography (PET) imaging allows detecting physical, chemical, and physiological changes related to metabolism . In dynamic PET studies, a common approach to identify different functional structures is by drawing manually regions‐of‐interest (ROIs) directly on PET images, and extracting the tissue time‐activity curves (TACs) for further analysis . The manual delineation of ROIs is, however, operator dependent, time‐consuming and challenging due to the inability of the operator to integrate the full TACs of the voxels in the evaluation and also due to noise in the PET images .…”