title: Anatomical accuracy of hybrid SPECT/spiral CT in the lower spine.
abstract: OBJECTIVE
  The anatomical accuracy of hardware-based registration of skeletal single photon emission computed tomography (SPECT) and X-ray computerized tomography (CT) has as yet not been studied. The aim of this study was to evaluate this variable in the lower spine for a newly introduced hybrid SPECT/spiral-CT camera.
  
  
  METHODS
  In 22 patients referred for degenerative joint disease or tumours, whole-body bone scintigraphy including hybrid SPECT/spiral CT of the lower spine was performed. Subsequent analyses were performed on these pairs of images as well as on data sets obtained after using a rigid automated fusion procedure in addition. Two observers independently measured the distances between the visually determined centres of gravity of the CT and SPECT representation of the fourth and fifth lumbar vertebral body in the X-, Y- and Z-directions (X-, Y- and Z-distances).
  
  
  RESULTS
  The distances determined by the two observers for the two vertebral bodies correlated significantly and were averaged for further analysis. For hybrid SPECT/spiral CT without consecutive automated registration, the mean X-, Y- and Z-distances were 1.6+/-1.9 mm, 1.7+/-1.3 mm and 0.9+/-0.5 mm, respectively. Additional automated registration lowered these values to 1.2+/-0.9 mm, 1.1+/-0.7 mm and 0.8+/-0.4 mm, respectively. The difference for the Y-distance proved statistically significant (P<0.05). Additional automated registration significantly reduced the number of subjects in whom at least one of the distances determined was greater than the SPECT pixel size of 4.6 mm from 14% (n=3) to 0% (P<0.05).
  
  
  CONCLUSIONS
  Hardware-based fusion between skeletal SPECT and CT offers a nearly perfect data match in the lower spine. The additional use of a tool for automated rigid registration has the potential to reduce the error of alignment even further and may be useful in patients with reduced compliance leading to movements between the two examinations.
authors.affiliation: Clinic of Nuclear Medicine, University of Erlangen/Nürnberg, Germany. Anton.Noemayr@nuklear.imed.unierlangen.de
authors.forename: Anton
authors.initials: A
authors.lastname: Nömayr
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Römer
authors.forename: Daniel
authors.initials: D
authors.lastname: Strobel
authors.forename: Werner
authors.initials: W
authors.lastname: Bautz
authors.forename: Torsten
authors.initials: T
authors.lastname: Kuwert
mesh_terms: D000368:Aged; D000465:Algorithms; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male; D015588:Observer Variation; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*