title: Retrospective registration of PET and MR brain images: an algorithm and its stereotactic validation.
abstract: OBJECTIVE
  We present a validation study of an algorithm for retrospective registration of PET and MR brain images.
  
  
  METHODS
  This algorithm involves two steps. In the first step, the two volumes are reformatted by aligning their interhemispheric fissure planes (midsagittal plane). In the second step, the corresponding planes parallel to the midsagittal plane are further aligned in the reformatted volumes to produce a 3D rigid body registration of the two original volumes. It is an efficient algorithm because both steps are performed in 2D spaces, and in each step only a small number of landmarks are required. A user-friendly system has been implemented to facilitate easy and fast processing of registration and reformatting of image volumes. The accuracy of this algorithm is validated using clinical scans of neurosurgical patients with a stereotaxic frame attached to their skull. The frame-based stereotaxic system provides an effective method for transforming image coordinates from different image volumes into a common coordinate system. This common coordinate system is used for assessing the spatial correspondence of each pixel in the registered image volumes. Validation using the stereotaxic image volumes enables objective estimation of retrospective registration accuracy.
  
  
  RESULTS
  Analysis of 11 MR/PET image pairs indicates that our registration method not only is efficient but also provides adequate accuracy for most clinical evaluation of PET studies.
  
  
  CONCLUSIONS
  We have implemented and validated an efficient algorithm for retrospective registration of PET and MR brain images.
authors.affiliation: Department of Psychiatry, Vanderbilt University, Nashville, Tennessee.
authors.forename: Y
authors.initials: Y
authors.lastname: Ge
authors.forename: J M
authors.initials: JM
authors.lastname: Fitzpatrick
authors.forename: J R
authors.initials: JR
authors.lastname: Votaw
authors.forename: S
authors.initials: S
authors.lastname: Gadamsetty
authors.forename: R J
authors.initials: RJ
authors.lastname: Maciunas
authors.forename: R M
authors.initials: RM
authors.lastname: Kessler
authors.forename: R A
authors.initials: RA
authors.lastname: Margolin
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology*; D001932:Brain Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging; D003847:Deoxyglucose / Q000031:analogs & derivatives; D005260:Female; D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D008961:Models, Structural; D015203:Reproducibility of Results; D013238:Stereotaxic Techniques / Q000295:instrumentation; D014055:Tomography, Emission-Computed
chemical_list: D005462:Fluorine Radioisotopes; D019788:Fluorodeoxyglucose F18; D003847:Deoxyglucose