ROBUST MULTIMODALITY REGISTRATION FOR BRAIN MAPPING

We present a robust intrasubject registration method for the synergist ic use of multiple neuroimaging modalities, with applications to magne tic resonance imaging (MRI), functional MRI, perfusion MRI, MR spectro scopy, and single-photon emission computed tomography (SPECT). This me thod allows user-friendly processing of difficult examinations (low sp atial resolution, advanced pathology, motion during acquisition, and l arge areas of focal activation). Registration of three-dimensional (3D ) brain scans is initially estimated by first-order moment matching, f ollowed by iterative anisotrophic chamfer matching of brain surfaces. Automatic brain surface extraction is performed in all imaging modalit ies. A new generalized distance definition and new specific methodolog ies allow registration of scans that cover only a limited range of bra in surface. A new semiautomated supervision scheme allows fast and int uitive corrections of possible false automatic registration results. T he accuracy of the MRI/SPECT anatomical-functional correspondence obta ined was evaluated using simulations and two difficult clinical popula tions (tumors and degenerative brain disorders). The average discrimin ation capability of SPECT (12.4 mm in-plane resolution, 20 mm slice th ickness) was found to be better than 5 mm after registration with MRI (5 mm slice thickness). Registration accuracy was always better than i maging resolution. Complete 3D MRI and SPECT registration time ranged between 6-11 min, in which surface matching represented 2-3 min. No re gistration failure occurred. In conclusion, the application of several new image processing techniques allowed efficient and robust registra tion. (C) 1997 Wiley-Liss, Inc.