Evaluation of elastic matching system for anatomic (CT, MR) and functional (PET) cerebral images

To evaluate the performance of our elastic matching system, we have created a digitized atlas from the brain of a normal young man, using 135 myelin-stained sections at 700 microns spacing. Software was written to enter and edit regional anatomic contours, which were stacked and aligned to create a three-dimensional atlas. We then evaluated the matching system by comparing computer generated contours with expert defined contours for several subcortical structures, based on CT scans from six neurologically normal patients. The error in positioning, as defined by the distance between the centers of gravity, averaged 4.2 mm for the computer and 1.7 mm for the worst expert's reading, with the computer drawn region frequently inscribed within that of the expert. Comparison was also made for each structure by determining the volume of overlap and the volumes not overlapping. On average, the computer's agreement with the experts was approximately 20% less than the agreement among the experts. This was a preliminary test of the system using only subcortical structures. The results are promising, and techniques are being implemented to overcome the current deficiencies.