Automated interhemispheric surface extraction in T1-weighted MRI using intensity and symmetry information.
BACKGROUND
Localizing the human interhemispheric region is of interest in image analysis mainly because it can be used for hemisphere separation and as a preprocessing step for interhemispheric structure localization. Many existing methods focus on only one of these applications.


METHODS
Here a new Intensity and Symmetry based Interhemispheric Surface extraction method (ISIS) that enables both applications is presented. A combination of voxel intensity and local symmetry is used to optimize a surface from T1-weighted MRI.


RESULTS
ISIS was evaluated in regard to cerebral hemisphere separation using manual segmentations. It was also evaluated in regard to being a preprocessing step for interhemispheric structure localization using manually placed landmarks.


METHODS
Results were compared to cerebral hemisphere separations by BrainVisa and Freesurfer as well as to a midsagittal plane (MSP) extraction method. ISIS had less misclassified voxels than BrainVisa (ISIS: 0.119±0.114%, BrainVisa: 0.138±0.084%, p=0.020). Freesurfer had less misclassified voxels than ISIS for one dataset (ISIS: 0.063±0.056%, Freesurfer: 0.049±0.044%, p=0.019), but failed to produce usable results for another. Total voxel distance from all manual landmarks did not differ significantly between ISIS and the MSP method (ISIS: 4.00±1.88, MSP: 4.47±4.97).


CONCLUSIONS
ISIS was found successful in both cerebral hemisphere separation and as a preprocessing step for interhemispheric structure localization. It needs no time consuming preprocessing and extracts the interhemispheric surface in less than 30 s.
Department of Radiology, Uppsala University, Uppsala University Hospital, SE-751 85, Uppsala, Sweden. Electronic address: richard.nordenskjold@radiol.uu.se.
Richard
R
Nordenskjöld
Department of Radiology, Uppsala University, Uppsala University Hospital, SE-751 85, Uppsala, Sweden.
Elna-Marie
EM
Larsson
Department of Radiology, Uppsala University, Uppsala University Hospital, SE-751 85, Uppsala, Sweden.
Håkan
H
Ahlström
Department of Radiology, Uppsala University, Uppsala University Hospital, SE-751 85, Uppsala, Sweden; AstraZeneca, Mölndal, Sweden.
Lars
L
Johansson
Department of Radiology, Uppsala University, Uppsala University Hospital, SE-751 85, Uppsala, Sweden.
Joel
J
Kullberg
D000368:Aged; D000369:Aged, 80 and over; D016477:Artifacts; D001921:Brain / Q000033:anatomy & histology*; D002535:Cerebral Aqueduct / Q000033:anatomy & histology; D016208:Databases, Factual; D001330:Electronic Data Processing; D006257:Head; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009434:Neural Pathways / Q000033:anatomy & histology; D012688:Septum Pellucidum / Q000033:anatomy & histology; D012984:Software; D013995:Time
Anterior commissure; Graph cut; Hemisphere separation; Interhemispheric surface; Midsagittal plane; Posterior commissure