title: The impact of transmission-emission misregistration on the interpretation of SPET/CT myocardial perfusion studies and the value of misregistration correction.
abstract: OBJECTIVE
  Previous studies indicate that the quality of single photon emission tomography/computed tomography (SPET/CT) myocardial perfusion imaging (MPI) is degraded by even mild transmission-emission misregistrations. The purpose of the current study was to investigate the impact of SPET/CT misalignment on the interpretation of MPI and examine the value of a commercial software application for registration correction.
  
  
  METHODS
  A total of 255 technetium-99m ((99m)Tc)-tetrofosmin stress/rest MPI examinations in 150 patients were reviewed for SPET/CT misalignment. After registration correction by the software, images were reassessed for interpretation differences from the misregistered study. The diagnostic benefit of reregistration was determined by taking into account the non-attenuation compensated image pattern, combined stress-rest evaluation, gated-SPET data and patient's history. In a phantom experiment and in 3 representative clinical cases, SPET/CT misalignment was purposely created by the software by sequential slice shifts and its effect was evaluated quantitatively.
  
  
  RESULTS
  Misregistration ≥1 pixel in at least one direction was observed in 24% of studies. Interpretation of MPI changed after registration correction in 11% of cases with misalignment <1 pixel, in 18% with 1-2 and in 73% with ≥2 pixels. The diagnostic information seemed to improve after registration correction in 58% of studies irrespective of the degree of misregistration. Software-simulated misregistration had dissimilar effects in the phantom and the 3 selected clinical cases.
  
  
  CONCLUSIONS
  The impact of SPET/CT misregistration on MPI interpretation although influenced by the degree and direction of slice misplacement, it is also case-specific and hardly predictable. Registration restoration by the software seems worthwhile regardless of misregistration magnitude.
authors.affiliation: University Hospital of Patras, Department of Nuclear Medicine, Rion Patras 265004, Greece. dimap@med.upatras.gr, dimap_med@hotmail.com.
authors.forename: Dimitris J
authors.initials: DJ
authors.lastname: Apostolopoulos
authors.forename: Martyna
authors.initials: M
authors.lastname: Gąsowska
authors.forename: Christos A
authors.initials: CA
authors.lastname: Savvopoulos
authors.forename: Theodoros
authors.initials: T
authors.lastname: Skouras
authors.forename: Trifon
authors.initials: T
authors.lastname: Spyridonidis
authors.forename: Andrzej
authors.initials: A
authors.lastname: Andrejczuk
authors.forename: Pavlos J
authors.initials: PJ
authors.lastname: Vassilakos
mesh_terms: D016477:Artifacts; D003324:Coronary Artery Disease / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D055414:Myocardial Perfusion Imaging / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*