Subtraction ictal SPECT co-registered to MRI improves clinical usefulness of SPECT in localizing the surgical seizure focus - O’Brien, TJ; So, EL; Mullan, BP; Hauser, MF; Brinkmann, BH; Bohnen, NI; Hanson, D; Cascino, GD; Jack, CR; Sharbrough, FW (Neurology, 1998)