Lesion segmentation and manual warping to a reference brain: Intra- and interobserver reliability

The study of subjects with acquired brain damage has been an invaluable too l fur exploring human brain function, and the description of lesion locatio ns within and across subjects is an important component of this method. Suc h descriptions usually involve the separation of lesioned from nonlesioned tissue (lesion segmentation) and the description of the lesion location in terms of a standard anatomical reference space (lesion warping). The object ives of this study were to determine the sources and magnitude of variabili ty involved in lesion segmentation and warping using the MAP-3 approach. Ea ch of two observers segmented the lesion volume in ten brain-damaged subjec ts twice, so as to permit pairwise comparisons of both intra- and interobse rver agreement. The segmented volumes were then warped to a reference brain using both a manual (MAPS) and an automated (AIR-3) technique. Observer ag reement between segmented and warped volumes was analyzed using four measur es: volume size, distance between the volume surfaces, percentage of nonove rlapping voxels, and percentage of highly discrepant voxels. The techniques for segmentation and warping produced high agreement within and between ob servers. For example, in most instances, the warped volume surfaces created by different observers were separated by less than 3 mm. The performance o f the automated warping technique compared favorably to the manual techniqu e in most subjects, although important exceptions were found. Overall, thes e results establish benchmark parameters fur expert and automated lesion tr ansfer, and indicate that a high degree of confidence can be placed in the detailed anatomical interpretation of focal brain damage based upon the MAP -3 technique. (C) 2000 Wiley-Liss, Inc.