title: Realignment of emission contaminated attenuation maps with uncontaminated attenuation maps for attenuation correction in PET.
abstract: OBJECTIVE
  We investigated aligning a transmission (T) scan with a subsequent emission contaminated transmission (T+E) scan. This would permit correction for patient motion and thereby use of a single T scan to correct E scans taken hours or days apart.
  
  
  METHODS
  Scans from 15 patients were used to produce 200 T scans contaminated with two levels of either [18F]fluorodeoxyglucose or [13N]ammonia E data. Known misalignments were introduced between each T+E scan and the corresponding T scan, and each pair was subsequently realigned. Realignment errors were compared with those obtained for uncontaminated T scans.
  
  
  RESULTS
  The realignment errors increase with the contamination level and depend slightly on the contaminant. However, even at the highest level of contamination studied, the mean absolute translation errors remained less than the voxel size and the mean absolute rotation errors were < 2.5 degrees.
  
  
  CONCLUSIONS
  AT+E scan can be accurately realigned with a T scan. This suggests that attenuation correction could be performed by using a high quality T scan taken days or hours earlier and aligning this T scan with a short T scan taken immediately after E imaging.
authors.affiliation: Department of Nuclear Medicine, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: I
authors.initials: I
authors.lastname: Buvat
authors.forename: N M
authors.initials: NM
authors.lastname: Freedman
authors.forename: V
authors.initials: V
authors.lastname: Dilsizian
authors.forename: S L
authors.initials: SL
authors.lastname: Bacharach
mesh_terms: D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D007089:Image Enhancement; D014055:Tomography, Emission-Computed / Q000379:methods*