“…Applications to volume measurement, three-dimensional (3D) visualization of data, and image feature analysis have been widespread (Condon et al, 1986;Gur et al, 1991;Jernigan et al, 1990;Jolles et al, 1989;Kerteaz et al, 1990;Pfefferbaum and Zipursky, 1991;Raine et al, 1990;Rusinek et al, 1991;Schwarzkopf et al, 1990;Seab et al, 1988;Simon et al, 1986;, and such techniques are now being used for practical applications such as drug trials and following the natural history of disease and response to therapy (Kikinis et al, 1992;Velthuzien et al, 1995;Mitchell et al, 1994Mitchell et al, , 1997Jackson et al, 1993;Vaidyanthan et al, 1995). The most prevalent techniques have used two or more images to enhance the information available from a single image alone and made use of analysis methods based upon cluster classification Cline et al, 1990Cline et al, , 1991Taxt et al, 1992;Brown et al, 1992;Gogahan et al, 1987;Vannier et al, 1985;Hyman et al, 1989;Jungke et al, 1988;Simmons et al, 1994;Bonar et al, 1993;Joliot and Mazoyer, 1993;Liang and MacFall, 1994;Taxt and Lundervold, 1994;Kao et al, 1996;Alfano et al, 1997;Bullmore et al, 1995).…”